Latest
Longer-form technical writing, published as it is finished and revised as field experience corrects it. Every entry carries its published and updated dates.
444 entries
PLC Architecture
How a programmable logic controller is physically organized: the chassis, backplane, processor, I/O modules, remote racks, and what those choices mean for wiring, expansion, and failure.
8 min readUpdated Sep 5, 2026
The PLC Processor
What the processor module does on every scan, how its memory is organized, what the mode switch and status lights mean, and how it faults and recovers.
8 min readUpdated Sep 5, 2026
Control Power Supplies
Sizing the 24 VDC supplies that run a controller and its field devices, separating loads that should not share a supply, and keeping the controller alive through a power event.
8 min readUpdated Sep 5, 2026
PLC I/O Systems
Discrete and analog input and output modules, sinking and sourcing, relay and transistor outputs, wiring conventions, and the module diagnostics that find field faults from the panel.
9 min readUpdated Sep 5, 2026
Controller Memory and Addressing
How a controller organizes its data: data tables and tags, the input and output images, the elementary data types and what they hold, and the naming discipline that keeps a program readable years later.
8 min readUpdated Sep 5, 2026
Tasks and Execution Priority
How a controller schedules its work: the continuous task, periodic tasks at a fixed rate, event tasks triggered by something happening, how priority preempts, and where each kind of logic belongs.
7 min readUpdated Sep 5, 2026
The Watchdog Timer
What the scan watchdog protects against, why it faults the controller instead of pausing it, what makes a scan run long, and why raising the limit is the wrong first response.
6 min readUpdated Sep 5, 2026
Retentive Memory
What survives a power cycle in a controller and what does not, how retention is backed up by battery, capacitor, or nonvolatile storage, what should be retentive, and how retained data gets lost.
8 min readUpdated Sep 5, 2026
IEC 61131-3
The standard behind PLC programming languages: the five languages, the common elements of data types, variables, and program organization units, what conformance actually means, and how the standard shows up in real platforms.
9 min readUpdated Sep 5, 2026
Structured Text
The text language of IEC 61131-3: syntax, control structures, how it fits alongside ladder, the conventions that keep it readable for the next person, and the mistakes that make structured text a liability in a plant that troubleshoots online.
10 min readUpdated Sep 5, 2026
Function Block Diagram
The graphical data-flow language of IEC 61131-3: how blocks, pins, and wires work, execution order, where FBD beats ladder and structured text, building reusable equipment blocks, and the habits that keep a diagram readable.
9 min readUpdated Sep 5, 2026
State Machines in PLC Programs
Writing sequences as explicit states instead of tangled interlock chains: what a state is, how transitions are written, the pattern in structured text and in ladder, publishing the state to the HMI, and the failure handling every state machine needs.
11 min readUpdated Sep 5, 2026
PLC Will Not Run
A controller that stays in program mode, faults on every attempt to run, or will not power up: the mode switch, the major fault log, the power supply, the memory and battery, the firmware and program mismatch, and the I/O configuration errors that stop a processor, in the order that finds them.
9 min readUpdated Sep 5, 2026
I/O Not Updating
Inputs that do not change and outputs that do not respond while the controller runs: the module and rack status, the inhibited and faulted connections, the input filter and the scan, the remote adapter link, the forced points, and the program that stopped writing the tag.
9 min readUpdated Sep 5, 2026
Permissives
The conditions that must be true before a device may start: how permissives differ from interlocks and trips, the list a pump or feeder usually needs, coding them so the HMI can say why a start was refused, and the rules for time delays and bypasses.
9 min readUpdated Sep 5, 2026
Sequencers
Step-based control for operations that always run in the same order: backwash, pump and valve startup, batch makeup, membrane cleans. What every step needs, three ways to implement one, handling faults and power loss mid-sequence, and what the HMI shows.
10 min readUpdated Sep 5, 2026
Program Organization
Structuring a controller program so that someone else can maintain it: a layout that follows the plant, one routine per job, standard device blocks, I/O mapped in one place, a fixed execution order, naming that means something, and comments that say why.
10 min readUpdated Sep 5, 2026
Control Strategies
Choosing how a loop is controlled before choosing how to program it: on-off with deadband, staging, PID, ratio and feedforward, cascade, split range, and override, with the water and wastewater applications each fits and the questions that pick between them.
11 min readUpdated Sep 5, 2026
Alarms in the Controller
Generating alarm conditions in the controller rather than in the graphics: why the PLC should own the alarm state, a standard alarm block with setpoints, deadband, and delays, equipment alarms, and packing alarm bits for SCADA.
9 min readUpdated Sep 5, 2026
Sequential Function Chart
The IEC 61131-3 language for sequences: steps, transitions, actions and their qualifiers, alternative and simultaneous branches, where it fits in water and wastewater, and the rules that keep a chart from sticking in a step.
9 min readUpdated Sep 5, 2026
Analog Signal Problems
The controller side of a bad analog value: raw counts against the module range, channel diagnostics, scaling that does not match the transmitter, wiring by device type, noise and filtering, resolution, and a symptom table that points at the check.
8 min readUpdated Sep 5, 2026
Communication Failures
What to read when a controller stops talking to a device, another controller, or SCADA: port and connection status, message error codes, timeouts and retries, addressing, limits, and the order of checks that separates controller, cable, device, and network.
8 min readUpdated Sep 5, 2026
Network Problems
The controller as a network device: addressing, duplicate addresses, link speed and duplex, connection limits, packet rate and storms, multicast for remote I/O, ring protocols, and time synchronization, with the diagnostics that show which is wrong.
8 min readUpdated Sep 5, 2026
Program Faults
Faults the program causes: an index out of range, division by zero, an invalid indirect address, a missing routine, a type mismatch, or task overlap. Reading the fault record, what a fault handler should do, clearing safely, and logic that does not fault.
8 min readUpdated Sep 5, 2026
Watchdog Faults
A task that did not finish in time: what the watchdog protects, why the scan grew, and how to fix it. Measuring task times, finding the loop or instruction that took the time, communications load, and when raising the watchdog is legitimate.
7 min readUpdated Sep 5, 2026
Modicon M340
Field notes on the Schneider Electric Modicon M340, a rack-based mid-range controller common in water plants: rack and CPU layout, X80 I/O, memory card behavior, Ethernet and serial communications, programming in Control Expert, and what to check on site.
8 min readUpdated Sep 5, 2026
Modicon M580
Field notes on the Schneider Electric Modicon M580, the Ethernet-backplane controller at the top of the range: remote I/O drops on a ring, hot standby CPUs, built-in security features, the networks it defines, Quantum migration, and what to check on site.
9 min readUpdated Sep 5, 2026
Control Expert
Field notes on Control Expert, the Schneider Electric engineering software for the Modicon M340 and M580: project structure, the five languages and derived function blocks, versions and files, online changes, upload information, and security settings.
8 min readUpdated Sep 5, 2026
Unity Pro
Field notes on Unity Pro, the earlier name of Control Expert and the software behind most installed Modicon M340, Quantum, and Premium applications: versions, moving projects to Control Expert, keeping an old version alive, and the Concept and PL7 originals.
7 min readUpdated Sep 5, 2026
ControlLogix
Field notes on the Rockwell Automation ControlLogix, the chassis-based controller of larger water plants: chassis and modules, tag-based memory and tasks, EtherNet/IP and older networks, controller redundancy, version matching, and what to check on site.
9 min readUpdated Sep 5, 2026
CompactLogix
Field notes on the Rockwell Automation CompactLogix, the smaller Logix controller behind most lift stations and small plants: families and I/O, the two Ethernet ports, what it shares with ControlLogix and what it lacks, and what to check on site.
8 min readUpdated Sep 5, 2026
Studio 5000
Field notes on Studio 5000, the Rockwell Automation software for ControlLogix and CompactLogix: the version-to-firmware rule, side-by-side installs, project files, add-on instructions, online editing, documentation in the controller, source protection.
8 min readUpdated Sep 5, 2026
Siemens
Field notes on Siemens controllers in water and wastewater: the S7-1200 and S7-1500 with TIA Portal, the older S7-300 and S7-400, PROFINET and PROFIBUS, the block model and memory cards, protection levels, and why it arrives inside packaged equipment.
8 min readUpdated Sep 5, 2026
AutomationDirect
Field notes on AutomationDirect controllers in water and wastewater: the Productivity, Do-more and BRX, and CLICK families with free software, the legacy DirectLOGIC line, Modbus and EtherNet/IP support, what they suit, and what to check on site.
8 min readUpdated Sep 5, 2026
Legacy Systems
Keeping older controllers running and planning a migration: the families still found in water plants, the risks that grow each year, software to keep alive, batteries and memory, tested spares, the security problem, and a migration the plant can survive.
9 min readUpdated Sep 5, 2026
Raw Counts
What an analog input module actually hands the program: the count range, where 4 mA and 20 mA fall in it, how under-range and over-range show up, and why the module manual is the only source that counts.
7 min readUpdated Sep 5, 2026
Filtering Analog Inputs
How to damp a noisy analog input in the controller without hiding a real process change: the first-order filter, the moving average, the median, where each belongs, and what never to filter.
8 min readUpdated Sep 5, 2026
Deadband and Hysteresis
Why a single setpoint chatters, how a deadband turns it into a start point and a stop point, how wide to make it, and where deadbands belong in alarms, level control, and controller outputs.
7 min readUpdated Sep 5, 2026
Signal Validation
Catching a failed analog input in logic before it runs a pump on a dead transmitter: range checks, module status bits, frozen-value detection, rate checks, and what the program does with a bad value.
8 min readUpdated Sep 5, 2026
Engineering Units
Choosing and documenting the units a tag carries: where the unit is decided, how it flows from transmitter range to controller scaling to screen and historian, the conventions used in water and wastewater, and the mismatches that put a wrong number on screen.
7 min readUpdated Sep 5, 2026
EtherNet/IP
How EtherNet/IP moves control data: CIP over standard Ethernet, implicit I/O connections on a requested packet interval, explicit messaging, producer and consumer tags, and what the network has to provide.
9 min readUpdated Sep 5, 2026
DNP3
The protocol built for utility telemetry: master and outstation, static and event data classes, unsolicited reporting, time-stamped events, and why it suits slow links that Modbus does not.
8 min readUpdated Sep 5, 2026
OPC UA
What OPC UA is for, how its information model, security, and transports differ from OPC Classic, where it belongs in a plant, and what to check before relying on it.
8 min readUpdated Sep 5, 2026
Serial Communications
RS-232, RS-422, and RS-485 in practice: which is which, cable and distance, termination, biasing, the common reference wire everyone leaves off, and the settings that have to match at both ends.
9 min readUpdated Sep 5, 2026
Protocol Gateways
Protocol converters between a controller and devices that do not speak its language: what a gateway does, the common pairings in water and wastewater, the mapping table that is the whole configuration, the failure modes a gateway adds, and when to use a native interface instead.
9 min readUpdated Sep 5, 2026
Remote I/O
Extending controller I/O to another panel or another site over a network: the adapter and the rack, the update rate and what it costs, what the outputs do when the link fails, the difference between remote I/O and a remote controller, and the wiring, addressing, and diagnostics that make it dependable.
9 min readUpdated Sep 5, 2026
ISA-101: Human Machine Interfaces
What the ISA-101 standard for human machine interfaces covers, its lifecycle from philosophy to maintenance, the display hierarchy, and what adopting it changes on a project.
8 min readUpdated Sep 5, 2026
SCADA Architecture
The parts of a SCADA system and how data moves between them: I/O servers, the tag database, clients, the historian, the alarm server, and the topologies from a single panel PC to a redundant, distributed plant.
9 min readUpdated Sep 5, 2026
Historians
What a process historian does that a database does not, how data gets into it, how compression and retrieval work, how to size and keep it, and the settings that quietly throw data away.
8 min readUpdated Sep 5, 2026
SCADA Redundancy
What redundant SCADA servers protect against and what they do not, how failover works for tags, alarms, history, and clients, the network and controller layers beneath it, and why an untested failover is not redundancy.
8 min readUpdated Sep 5, 2026
The Alarm Philosophy
The document that decides what is allowed to be an alarm: the definition, the criteria, the priorities and their meaning, the performance targets, the handling rules, and who owns it. Under ISA-18.2 it comes first.
9 min readUpdated Sep 5, 2026
Alarm Priority
How to assign alarm priorities that operators trust: a consequence-and-time matrix, three or four levels, the target distribution from ISA-18.2 and EEMUA 191, and the mistakes that make every alarm high.
9 min readUpdated Sep 5, 2026
Alarm Rationalization
The meeting where every alarm earns its place: who attends, what is decided for each alarm, how to document it in a master alarm database, and how to run it at a utility that cannot spare a week.
10 min readUpdated Sep 5, 2026
Alarm Floods
What an alarm flood is, why it happens at exactly the wrong moment, the ISA-18.2 rate targets, and the design measures that keep a power failure or a communication loss from burying the one alarm that matters.
10 min readUpdated Sep 5, 2026
Alarm Notification and Callout
Getting the alarm to the person on call when no one is watching the screen: notification paths, escalation, acknowledgment from the field, which alarms qualify, and the failure modes that leave a station in high level with nobody paged.
10 min readUpdated Sep 5, 2026
HMI Faceplates
The pop-up that controls one device: what a pump, valve, or loop faceplate must show, the mode and command layout, interlock and permissive display, security by role, and building faceplates from a standard object so every device behaves the same.
10 min readUpdated Sep 5, 2026
Trends on the HMI
Trend displays that answer questions: embedded sparklines on process displays, pre-configured trend groups, the axes and time spans that make a trend readable, and the difference between a trend for operating and a trend for investigating.
9 min readUpdated Sep 5, 2026
Alarm Indication on the HMI
How an alarm looks and sounds on the operator screen: the ISA-101 and ISA-18.2 rules for color, shape, and blink, the alarm banner and summary, acknowledgment behavior, navigation to the alarm, and indication that survives colorblindness and a noisy control room.
10 min readUpdated Sep 5, 2026
HMI Navigation
How operators move through the displays: the display hierarchy from overview to detail, a fixed navigation bar with area alarm indication, one-click paths from an alarm to the device, the rules that keep any display within two clicks, and what to leave out.
9 min readUpdated Sep 5, 2026
Historian Architecture
How process history is collected, stored, and served: the collector, the archive, and the client layers, where the historian sits relative to SCADA and the DMZ, single-server and tiered designs for a utility, the store-and-forward buffer that survives outages, and the sizing that decides how many years fit on a disk.
9 min readUpdated Sep 5, 2026
Historian Data Collection
Deciding what the historian stores and how often: polled versus exception collection, the deadband per tag, rates for control loops, levels, totals, and compliance values, timestamps at the source, quality codes, calculated tags, and the tag list review that keeps a historian from filling with noise and missing what matters.
9 min readUpdated Sep 5, 2026
Historian Compression
How historians store years of data on a disk: exception deadbands at the collector, swinging door compression at the archive, what each discards and what it keeps, the settings that turn a trend into a staircase, lossless alternatives, and how to check that the compressed data still tells the truth.
8 min readUpdated Sep 5, 2026
Reporting from the Historian
Turning history into the reports a utility must produce: the monthly operating report, compliance reports for the regulator, daily operator summaries, pump run and energy reports, the calculations behind daily minimums, maximums, and totals, handling bad quality and gaps, and building reports once so they run every month without an engineer.
9 min readUpdated Sep 5, 2026
SCADA Servers
What the servers in a SCADA system do and what a utility should expect of them: the I/O, alarm, historian, and client roles, physical versus virtual, redundancy, sizing, placement, backup, patching, licensing, and monitoring.
10 min readUpdated Sep 5, 2026
SCADA Clients
The workstations, browsers, and mobile devices operators use to see and control the system: thick, thin, web, and mobile clients, roles and permissions, where control is allowed from, workstation design, session policy, licensing, and failover behavior.
9 min readUpdated Sep 5, 2026
Alarm Servers
The part of SCADA that turns a condition into an alarm and manages its life: where detection happens, the alarm state machine, priority, deadband and delays, acknowledgment across clients, the journal, notification, redundancy, timestamps, and flood behavior.
10 min readUpdated Sep 5, 2026
SCADA Communications
How SCADA servers talk to controllers and the field: polling and report by exception, the protocols and what each is for, media from plant Ethernet to radio and cellular, poll rate arithmetic, timeouts and quality, time sync, store and forward, and security.
11 min readUpdated Sep 5, 2026
Color in HMI Design
How color is used on a high performance HMI: a gray palette for normal operation so that color means something, alarm colors reserved by priority, equipment state by fill and text rather than red and green, color-blind safe choices, and the palette table.
9 min readUpdated Sep 5, 2026
Situational Awareness
Designing displays so an operator knows what is happening, what it means, and what comes next: the three levels of awareness, the display hierarchy, analog indicators with normal ranges, embedded trends, time-to-limit predictions, and a test for any display.
10 min readUpdated Sep 5, 2026
Alarm Shelving
The operator tool for temporarily silencing a nuisance alarm: what shelving is and is not, the rules a philosophy sets, who may shelve what and for how long, automatic unshelving, the shelved list, the record, and how to implement it on any platform.
8 min readUpdated Sep 5, 2026
Alarm Suppression
Suppressing alarms by design: state-based logic that removes alarms that mean nothing in the current state, parent-child logic that stops a flood at its source, out-of-service suppression for maintenance, the rules that keep it safe, and how to test it.
9 min readUpdated Sep 5, 2026
Trending
Using historian trends to understand a process and diagnose a problem: pens that belong together, scaling and time ranges, raw versus averaged data and what compression hides, overlays and cursors, event markers, and the patterns that point at each cause.
9 min readUpdated Sep 5, 2026
Frozen Values
Why a SCADA value stops changing while looking normal: the five layers where it can freeze, from a transmitter holding its output to a client that lost its server, how to find the layer by comparing each, and the heartbeat that makes a freeze announce itself.
9 min readUpdated Sep 5, 2026
Lost Communications
What should happen when SCADA loses a device, a site, or everything, how the pattern tells which, the diagnostic order from the server outward through network, firewall, medium, and site, and the design that makes a lost link an alarm rather than an incident.
9 min readUpdated Sep 5, 2026
Bad Quality
What a quality flag means and where it comes from: good, uncertain, and bad with substatus codes, how quality propagates from device through driver, tag, display, alarm, and historian, the causes by layer, and the rule that a bad value is never a number.
9 min readUpdated Sep 5, 2026
Server Failure
How SCADA servers fail and what to do when one does: failure modes from a full disk to a dead hypervisor host, what the plant experiences with and without redundancy, the recovery sequence from restore to alarm verification, and the monitoring that warns.
9 min readUpdated Sep 5, 2026
Client Problems
Diagnosing the operator station rather than the system: a client that will not connect, shows nothing, runs slowly, freezes, or stays silent on an alarm, with the causes, the order of checks, and the standard build and spare that make the fix a swap.
8 min readUpdated Sep 5, 2026
Historian Problems
How a historian goes wrong and how to find each fault: gaps, wrong values, detail never stored, disks that fill, slow queries, backfill that never arrives, and unreadable archives, with the collector, queue, configuration, and storage checks that locate it.
9 min readUpdated Sep 5, 2026
Alarm Problems
How an alarm system fails: alarms that never raise, raise unheard, stick, chatter, or flood, acknowledgments that do not propagate, and notifications that never arrive, with the causes by layer and the end-to-end test that proves the whole chain.
9 min readUpdated Sep 5, 2026
Time Synchronization
Why every clock in a control system must agree and what happens when they do not: out-of-order events, historian gaps at daylight saving, authentication failures, wrong totals. The time source and hierarchy, how each device is synchronized, and the checks.
9 min readUpdated Sep 5, 2026
Long-Term Storage
Keeping historian data for years: a retention policy by data class that follows the record rules, tiered storage from online to offline copies, downsampling, archive management, exports that outlive the historian, and the annual proof that old data reads.
9 min readUpdated Sep 5, 2026
SQL Integration
Connecting SCADA and historian data to relational databases: why a utility does it, the methods, a schema that handles time series, the query patterns for totals and reports, the mistakes that flood a database or stall a server, and security.
10 min readUpdated Sep 5, 2026
VTScada
Field notes on VTScada, the Trihedral platform widely used by municipal water utilities: the all-in-one design with historian, alarm notification, and thin clients built in, server redundancy, application versioning, telemetry drivers, and licensing by tags.
8 min readUpdated Sep 5, 2026
Ignition
Field notes on Ignition from Inductive Automation: gateway and modules, unlimited licensing per server, Perspective and Vision clients, the SQL-based historian, Python scripting, redundancy, Edge for small sites, and what to decide before building on it.
8 min readUpdated Sep 5, 2026
GE iFIX
Field notes on iFIX, the long-established SCADA from the Intellution and GE lineage now sold by GE Vernova: SCADA nodes and the process database, I/O drivers, view and web clients, the Proficy Historian, enhanced failover, scripting, and licensing by points.
8 min readUpdated Sep 5, 2026
AVEVA
Field notes on the AVEVA operations software family, formerly Wonderware: InTouch HMI, System Platform and its object model, the Historian, Plant SCADA from the Citect lineage, and AVEVA Edge. Which product does what, and what to check on site.
8 min readUpdated Sep 5, 2026
Rockwell FactoryTalk
Field notes on the Rockwell Automation FactoryTalk family: View Site Edition and Machine Edition, the directory, Linx with direct controller tag access, device-based Alarms and Events, the PI-based Historian, ViewPoint and Optix, redundancy, and site checks.
8 min readUpdated Sep 5, 2026
Schneider SCADA
Field notes on Schneider Electric SCADA for water: EcoStruxure Geo SCADA Expert, formerly ClearSCADA, the telemetry platform built around DNP3 events, an object database, and hot standby servers, with SCADAPack RTUs, and how it relates to the AVEVA products.
8 min readUpdated Sep 5, 2026
Other Platforms
The SCADA and HMI products a water utility may meet beyond the common ones: Siemens WinCC, distributed control systems, independent SCADA products, hosted lift station monitoring, and open-source tools, and the questions that decide whether one belongs.
8 min readUpdated Sep 5, 2026
4-20 mA Signals from the Instrument Side
How a 4-20 mA current loop is powered and wired at the transmitter, why the loop resistance budget matters, and how to check a loop with a meter.
9 min readUpdated Sep 5, 2026
Wet Well Level Measurement
How lift station wet well level is measured, which technology suits which well, the failure modes that flood a station, and why the high level float must stay hardwired.
8 min readUpdated Sep 5, 2026
Hydrostatic Level Measurement
Measuring level from the pressure of the liquid above a sensor: submersible transducers, bubblers, and base-mounted transmitters, the density assumption behind all of them, venting, installation, and what makes them drift.
8 min readUpdated Sep 5, 2026
Ultrasonic Level Measurement
Non-contact level by time of flight: how the sensor works, the blanking zone and beam angle, temperature compensation, the surfaces and vapors that defeat it, mounting rules, and what to do when it loses its echo.
8 min readUpdated Sep 5, 2026
Float Switches
The oldest level instrument and still the one that saves a station: how tilt and stem floats work, the wiring conventions, mounting and spacing in a wet well, classified-area ratings, and how to use them alongside a continuous instrument.
7 min readUpdated Sep 5, 2026
Pressure Transmitters
Gauge, absolute, and differential pressure transmitters: how they sense, how range, turndown, and accuracy specifications work, the process connection and its accessories, and the installation errors that show up as calibration problems.
8 min readUpdated Sep 5, 2026
HART
Digital data riding on the 4-20 mA loop: how HART signaling works, what a handheld or a HART-enabled input can read, multidrop and burst modes, and the wiring conditions that make HART fail while the current loop keeps working.
10 min readUpdated Sep 5, 2026
Differential Pressure Flow Measurement
Orifice plates, venturis, and flow nozzles: the square-root relationship, why turndown is limited, where the square root is taken, impulse line rules, and when a DP element is still the right choice against a mag meter.
10 min readUpdated Sep 5, 2026
Open Channel Flow Measurement
Flumes and weirs with a level sensor: how the head-discharge relationship works, Parshall flume and weir equations, where to put the sensor, submergence, and the errors that make a permit-reporting flow meter wrong.
11 min readUpdated Sep 5, 2026
Chlorine Residual Analyzers
Amperometric and colorimetric residual analyzers: what each measures, free versus total chlorine, pH and flow dependence, sample line design, calibration against a DPD grab sample, and using the signal for feed control.
11 min readUpdated Sep 5, 2026
pH Measurement
Glass electrodes, reference junctions, and why pH is the measurement that drifts: how the sensor works, temperature compensation, two-point buffer calibration, mounting rules, the failure modes of the reference, and using the signal for chemical feed control.
11 min readUpdated Sep 5, 2026
Dissolved Oxygen Measurement
Optical and membrane DO sensors for aeration control: how each measures, why optical has taken over, air calibration with pressure and salinity corrections, sensor placement in an aeration basin, fouling and cleaning, and the response time that limits the control loop.
11 min readUpdated Sep 5, 2026
Turbidity Measurement
Nephelometric turbidimeters for filter effluent and raw water: how 90-degree scattering is measured, the methods and the NTU, low-range versus high-range instruments, bubbles and the debubbler, formazin calibration and verification standards, and the compliance record the instrument exists to produce.
11 min readUpdated Sep 5, 2026
Surge Protection for Signal Circuits
Protecting 4-20 mA loops, discrete inputs, network cables, and radio feeds from lightning and switching surges: where surges enter, the device types and how they clamp, the grounding that makes them work, the resistance and capacitance they add, and where to put them at a remote site.
10 min readUpdated Sep 5, 2026
Loop Checks
Proving every I/O point end to end before a system goes live: what a loop check is and is not, the three-point analog check, discrete and output checks, the two-person method with the sheet that records it, what to do with a point that fails, and why a loop check is not a calibration.
9 min readUpdated Sep 5, 2026
Calibration Procedures
How a utility calibrates its instruments consistently: the as-found and as-left discipline, tolerance from the loop rather than the data sheet, the reference standard and its traceability, the five-point check with hysteresis, adjusting only when needed, intervals set from history, and the procedure written once per instrument type.
9 min readUpdated Sep 5, 2026
Calibration Documentation
The records a calibration program produces and what each is for: the calibration certificate per event, the instrument history, the reference standard file, the schedule, the tolerance and interval register, and how the records are organized so a regulator, an auditor, or the next technician can find what they need.
8 min readUpdated Sep 5, 2026
Impulse Lines
The tubing between the process tap and the pressure or DP transmitter, and everything that goes wrong in it: slope and routing for liquid and gas, elevation head and how to correct for it, air and condensate, blocking and manifold valves, freezing, plugging on dirty service, and the diaphragm seal alternative.
9 min readUpdated Sep 5, 2026
Ultrasonic Flowmeters
Transit-time and Doppler ultrasonic flow measurement: how each works, which liquids each suits, clamp-on versus wetted transducers, the pipe data the meter needs, the accuracy to expect, and the installation details that decide whether to trust the reading.
10 min readUpdated Sep 5, 2026
Flowmeter Installation
The installation rules that decide whether a flowmeter reads correctly: straight run by meter type, keeping the pipe full, orientation, velocity range, grounding for magnetic meters, isolation and access, and the commissioning checks that prove the meter.
10 min readUpdated Sep 5, 2026
Flow Troubleshooting
A method for a flow reading that is wrong, noisy, zero, or disputed: establish the truth with an independent check, separate installation from configuration from signal chain, then the specific checks for magnetic, ultrasonic, and DP meters.
10 min readUpdated Sep 5, 2026
Differential Pressure Level
Measuring level in a closed or pressurized vessel with a DP transmitter: high and low side connections, dry legs and wet legs, zero suppression and elevation, the range calculation with a worked example, remote seals, and the density dependence.
10 min readUpdated Sep 5, 2026
Level Troubleshooting
A method for a level reading that is wrong, frozen, jumping, or lost: establish the true level, check the signal chain and configuration, then the checks for ultrasonic, radar, hydrostatic, DP, and float instruments, and the failure behavior to design in.
10 min readUpdated Sep 5, 2026
Differential Pressure
The differential pressure transmitter as an instrument: what it measures, static and overrange ratings, the three-valve manifold and the order of operations that protects the cell, and the applications from filter head loss to membrane TMP, flow, and level.
9 min readUpdated Sep 5, 2026
Pressure Transmitter Installation
Where and how to install a pressure transmitter so it reads the process and not its own plumbing: tap location, mounting above or below the tap, isolation and bleed valves, line slope, pulsation, elevation, freeze protection, seals, vibration, and sun.
10 min readUpdated Sep 5, 2026
Pressure Calibration
What calibrating a pressure transmitter means: as-found and as-left, the five-point test and hysteresis, tolerance and the reference standard, sensor trim versus output trim versus reranging on a smart transmitter, gauge versus absolute, and intervals.
10 min readUpdated Sep 5, 2026
Ammonia Analyzers
Online ammonia measurement in water and wastewater: ion-selective probes, gas-sensing electrodes, and wet-chemistry analyzers, what each is good for, the interferences that decide accuracy, and the maintenance and calibration it demands.
9 min readUpdated Sep 5, 2026
Conductivity
Conductivity measurement in water systems: what it indicates, contacting and inductive sensors, cell constants and ranges, temperature compensation, the relation to total dissolved solids, uses from membrane monitoring to blending, and fouling problems.
8 min readUpdated Sep 5, 2026
Nitrate Analyzers
Online nitrate measurement: ultraviolet absorbance probes and analyzers, ion-selective electrodes, and wet chemistry, the interferences from organics, turbidity, and chloride, the uses in denitrification and source monitoring, and maintenance.
8 min readUpdated Sep 5, 2026
ORP
Oxidation-reduction potential: what the millivolt reading means and does not, the platinum and reference pair, uses in dechlorination control, disinfection indication, anoxic monitoring, and chemical treatment, checking with standards, and electrode drift.
7 min readUpdated Sep 5, 2026
Calibration Troubleshooting
When an instrument will not calibrate or stay calibrated: wrong or expired standards, slope and offset out of range, compensation errors, procedure mistakes, loop scaling that disagrees with the instrument, and deciding when to adjust, replace.
8 min readUpdated Sep 5, 2026
Digital Signals
Discrete signals between instruments and controllers: dry and wetted contacts, sinking and sourcing transistor outputs, two-wire sensor leakage, NAMUR sensors with wire-break detection, contact ratings at low current, and wiring conventions.
8 min readUpdated Sep 5, 2026
Frequency Signals
Frequency as a process signal: the instruments that produce it, how frequency differs from pulse counting, the K-factor and the conversion to flow, frequency inputs and period measurement at low rates, converters to 4-20 mA, noise, and how to verify one.
7 min readUpdated Sep 5, 2026
Pulse Signals
Pulse outputs for totalizing: flowmeters, energy meters, rain gauges, and feeders, output types, scaling in volume per pulse, counter inputs, pulse width and rate, debouncing reeds, totalizer retention and rollover, and verifying against the register.
7 min readUpdated Sep 5, 2026
Signal Isolation
Isolating analog signals: loop isolators and their variants, splitters that feed two receivers, converters, the common-mode problem isolation solves, ratings, accuracy and response costs, and when an isolated input module makes the isolator unnecessary.
8 min readUpdated Sep 5, 2026
Short-Circuit Current Rating (SCCR)
What a control panel’s short-circuit current rating means, how it is determined under UL 508A, why the NEC requires it on the label, and why the number is usually smaller than people expect.
9 min readUpdated Sep 5, 2026
Enclosure Selection
Choosing the box: NEMA and UL 50 type ratings, materials for corrosive and outdoor sites, sizing for heat and wire bending space, and the details at the conduit entries and the door that decide whether the rating survives installation.
8 min readUpdated Sep 5, 2026
Enclosure Heat Calculations
Estimating the temperature inside a control panel from the power its contents dissipate and the surface that carries it out, what to do when the answer is too hot, and why drives change everything.
8 min readUpdated Sep 5, 2026
Component Layout
Arranging a panel so it is safe to work in, cool enough to run, quiet enough for its signals, and possible to modify: power and control separation, heat, wireways, terminals, and the working space rules.
8 min readUpdated Sep 5, 2026
Hand-Off-Auto Selectors
What each position of an HOA selector does, how it is wired into the starter circuit, which protections must survive Hand, what the controller should see, and the mistakes that let a pump run with nobody watching.
7 min readUpdated Sep 5, 2026
Variable Frequency Drives in Pump Panels
What a drive adds to a pump panel and what it costs: speed control, soft start, reduced inrush, and diagnostics against heat, harmonics, cable and motor stress, bypass, and the minimum speed below which a pump does no work.
11 min readUpdated Sep 5, 2026
Soft Starters
Reduced-voltage solid-state starters: how they ramp a motor, what they do for inrush, water hammer, and mechanical stress, where they beat a drive and where they do not, bypass contactors, and the settings that matter on a pump.
9 min readUpdated Sep 5, 2026
Circuit Breakers in Control Panels
Miniature, molded-case, and supplementary protectors: what each is listed to do, how a trip curve is read, where the NEC and UL 508A set the rules, and how breaker choice drives the short-circuit current rating of the whole panel.
10 min readUpdated Sep 5, 2026
Fuses in Control Panels
Fuse classes, time-delay and fast-acting types, current limitation and what it does for the panel short-circuit rating, semiconductor fuses for drives, control circuit and DC fusing, and the habits that make a blown fuse a diagnosis instead of a mystery.
10 min readUpdated Sep 5, 2026
Panel Power Supplies
The 24 V DC supply behind everything in a modern panel: sizing with real inrush and duty, single versus redundant with diode modules, how a switch-mode supply behaves under a short, distribution and fusing per branch, monitoring, and the failure modes that take out a whole panel at once.
9 min readUpdated Sep 5, 2026
Control Relays
The interposing and logic relays in a control panel: why a controller output drives a relay instead of a starter coil, contact ratings and the difference between resistive and inductive loads, coil suppression, ice cube relays versus terminal relays versus solid-state, and the failure modes that make a relay the first suspect in a dead circuit.
8 min readUpdated Sep 5, 2026
Terminal Blocks
The point where field wiring meets the panel: screw, spring, and push-in terminals, ratings and the UL 1059 groups, fused and disconnect terminals for instrument loops, grounding terminals, multi-level blocks, jumpers and marking, and the layout that makes a loop check or a field change a five-minute job.
8 min readUpdated Sep 5, 2026
UPS for Control Panels
Keeping the controller, the radio, and the SCADA server alive through an outage: AC and DC UPS types, what to put on the UPS and what not to, sizing for runtime and inrush, the battery as a maintenance item, the alarms a UPS must provide, and what happens when the UPS is the thing that fails.
8 min readUpdated Sep 5, 2026
Noise Problems
Electrical noise as a panel problem: the four ways it couples, the design features that keep it out, the sources people forget such as unsuppressed coils and unbonded doors, and the sequence for finding where noise gets into a panel that should be clean.
10 min readUpdated Sep 5, 2026
Ground Faults
Ground faults in and around control panels: what happens on grounded 120 VAC circuits, on grounded and ungrounded 24 VDC systems, and on drive outputs; where they hide, from chafed wire to flooded boxes; and the divide-and-conquer method that finds them.
10 min readUpdated Sep 5, 2026
No Control Power
The control power path from the disconnect to the last relay, and how to work along it when the panel is dead: transformer and fuses, control breaker, emergency stop and safety relay, DC supply and distribution, what trips them, and design that makes it easy.
10 min readUpdated Sep 5, 2026
NFPA 70 and the Control Panel
The National Electrical Code inside an industrial control panel: Article 409 and the listing it points to, the short-circuit current rating, overcurrent protection for control circuits, grounding and bonding, working space, and what an inspector asks.
9 min readUpdated Sep 5, 2026
UL 698A
Industrial control panels for hazardous locations: what UL 698A adds to UL 508A, a panel in a classified area or a safe-area panel with intrinsically safe circuits, barriers and isolators, the control drawing, and where utilities meet classified areas.
8 min readUpdated Sep 5, 2026
Wireways
Panel wireway design: fill limits and the space terminations need, separating power, control, and signal wiring, routing around heat and drives, sizing rules, the cases where wireway is the wrong choice, and the habits that keep a panel serviceable.
7 min readUpdated Sep 5, 2026
Terminals
Designing the terminal strips of a control panel: grouping by voltage and function, numbering that matches the drawings, fused and disconnect terminals for instrument loops, shield and ground terminals, spares, ferrules and torque, and the terminal schedule.
7 min readUpdated Sep 5, 2026
Surge Devices
Surge protective devices in a control panel: the types and where each belongs, the ratings that matter, supply protection, signal and network protection on conductors that leave the building, stage coordination, grounding, indication, and replacement.
8 min readUpdated Sep 5, 2026
Network Switches
Selecting and installing the Ethernet switch in a control panel: managed against unmanaged, industrial ratings and DIN rail mounting, ports and media including fiber, ring protocols, power and grounding, and the configuration documented with the panel.
8 min readUpdated Sep 5, 2026
Blown Fuses
Working a blown fuse in a control panel: reading the circuit before replacing anything, fault against overload, finding a short by sectioning, the transformer and power supply cases, fuse types that must match, indicating holders, and replacement rules.
8 min readUpdated Sep 5, 2026
Failed Power Supplies
Diagnosing the 24 volt supply in a control panel: dead, low, noisy, or cycling, a failed supply against an overloaded one, loads that grew, heat and capacitor aging, redundant supplies, sag on the input, and what to specify so the next failure is an alarm.
8 min readUpdated Sep 5, 2026
Panel PLC Faults
Working a controller fault from the panel side: reading the indicators before opening the software, faults caused by the panel rather than the program, power and grounding, I/O module and wiring faults, heat, loose connections, and the order of checks.
8 min readUpdated Sep 5, 2026
Relay Problems
Diagnosing control relays in a panel: contacts that do not make or that weld, coils that fail or chatter, drop-out on sag, interposing relays on controller outputs, loads that burn contacts, suppression, sockets, and replacing against fixing the cause.
7 min readUpdated Sep 5, 2026
PLC Power
Powering the controller section of a panel: the control transformer and 24 volt supplies, separating controller power from field I/O power, sizing with margin, the UPS and what rides through, protection and monitoring, the DC ground, and restart sequencing.
8 min readUpdated Sep 5, 2026
Panel I/O
Arranging the I/O in a controller panel: module types for the field devices, sinking, sourcing, and isolated inputs, fused and relay outputs, the path from field terminal to module, spare capacity, and addressing that follows the I/O list.
8 min readUpdated Sep 5, 2026
Relays in the PLC Panel
The relays a controller panel needs and why: interposing relays between outputs and loads, input relays for high-voltage and remote signals, isolation and safety relays, monitoring relays, coil and contact selection, and keeping logic out of relays.
7 min readUpdated Sep 5, 2026
Isolation
Isolating the controller from the field: why grounds differ and what that does to signals, signal isolators and isolated channels, isolation transformers and their limits, relays as isolation, fiber as the ultimate isolator, and when isolation is worth it.
8 min readUpdated Sep 5, 2026
Panel Surge Protection
Surge protection of a controller panel as a system: a single entrance and the ground bar it lands on, staged protection on the power, protectors on every loop and data line that leaves the building, the radio feed, layout, and the checklist after a strike.
8 min readUpdated Sep 5, 2026
Panel Networking
The network inside a controller panel: which networks exist and how they are kept apart, where the switch sits, copper patching and fiber entry, the radio or cellular router as a panel component, cable management, shield grounding, and labeling.
7 min readUpdated Sep 5, 2026
Duplex Pump Panels
The duplex control panel: two pumps on one wet well and the sections every duplex panel contains, from power and starters through level control, alternation, hand-off-auto, alarms, and the backup float circuit to telemetry, with the failure responses.
9 min readUpdated Sep 5, 2026
Triplex Pump Panels
The triplex control panel: three pumps on one wet well, the alternation schemes that keep three pumps evenly used, staging levels and standby logic, power, drives and their coordination, the backup circuit for three pumps, and what a duplex never decides.
8 min readUpdated Sep 5, 2026
Alternation
Pump alternation at the panel level: what it is for, the alternator relay against controller logic, schemes from alternate-every-cycle to runtime balancing, manual lead selection, skipping a failed pump, alternation in the backup circuit, and the tests.
7 min readUpdated Sep 5, 2026
Distribution Pressure Control
How a booster or high service pump station holds discharge pressure with variable speed pumps, how pumps are staged, and what stops the system hunting.
9 min readUpdated Sep 5, 2026
Tank Level Control
How a storage tank is filled and drawn on level setpoints, how the setpoints are chosen to keep the water turning over, and what the station does when the tank stops talking.
8 min readUpdated Sep 5, 2026
Lift Station Lead/Lag Control
How a duplex or triplex station decides when one pump is enough and when it is not: the setpoint ladder, cycle volume, the lag call, parallel pumping, and what to do when the lead pump fails.
12 min readUpdated Sep 5, 2026
Lift Station Pump Alternation
Which pump leads, how the lead role rotates, what an alternator relay does, and why equal run hours are not always the goal. Includes the logic rules that keep alternation from causing trouble.
10 min readUpdated Sep 5, 2026
Lift Station High Level
The alarm that stands between a lift station and an overflow: where the high-level float goes, what it must do on its own, how much response time the well provides, and how to diagnose a high level that should not be happening.
11 min readUpdated Sep 5, 2026
Lift Station Backup Control
How a lift station keeps pumping when the transmitter, the PLC, or the SCADA link is gone: float backup logic, the control transfer relay, redundant-off protection, and how to test it with the controller actually dead.
12 min readUpdated Sep 5, 2026
Wet Well Level PID Control
Holding a wet well level with a variable speed pump instead of bang-bang control: the loop structure, the minimum speed floor, the stop and restart logic at low inflow, tuning for a slow integrating process, and where level PID is the wrong idea.
11 min readUpdated Sep 5, 2026
VFD Pump Control in Wastewater
The control modes for a variable speed wastewater pump: level control, flow pacing, fixed speed with soft start, and drawdown modes, plus the wastewater-specific rules: minimum speed, ragging at low speed, force main velocity, and the periodic full-speed run.
10 min readUpdated Sep 5, 2026
Triplex Lift Station Controls
What changes when a station has three pumps: the lead, lag, and standby roles, rotation with three positions, the diminishing return of the third pump on the system curve, availability logic, and the power and panel arrangements that three pumps require.
10 min readUpdated Sep 5, 2026
Lift Station Generator Operation
Standby power at a lift station: what the transfer switch does, how the controls ride through the transfer, staggered pump restarts, what SCADA should see, load testing, and the portable generator connection.
10 min readUpdated Sep 5, 2026
Well Pump Control
Controlling a groundwater well: submersible and line-shaft turbine pumps, the pump-to-waste start, drawdown and the low-water cutoff, cycling limits from the well and the aquifer, and what the controller monitors to protect a pump that cannot be seen.
10 min readUpdated Sep 5, 2026
Booster Pump Stations
Inline stations that raise pressure from one zone to another: suction pressure protection, discharge pressure control with drives, staging, the hydropneumatic tank alternative, surge and check valve behavior, and the interlocks that keep a booster from collapsing the zone it draws from.
9 min readUpdated Sep 5, 2026
Elevated Tank Control
The tank on legs that sets the zone pressure: how level equals pressure, the operating band, the altitude valve and its telemetry, turnover for water quality, filling by pumps far away, freeze protection, and what the level signal does when the tank is holding the system together.
10 min readUpdated Sep 5, 2026
Disinfection Control
Controlling chlorine and chloramine dosing at a water plant: the CT concept and how contact time is credited, flow-paced and residual-trimmed feed, gas, hypochlorite, and on-site generation systems, the point-of-entry residual as the compliance measurement, and the interlocks that stop a feed system from over- or under-dosing.
11 min readUpdated Sep 5, 2026
Aeration Control
Controlling the largest energy user at a wastewater plant: the DO cascade to airflow, blower staging and turndown, most-open-valve pressure control across basins, ammonia-based aeration control, the instruments each strategy depends on, and the interlocks that keep blowers out of surge.
11 min readUpdated Sep 5, 2026
Headworks Control
The first stop for raw wastewater: influent flow measurement, mechanical screens and their differential level control, grit removal, influent pumping where the plant needs it, the odor and hazardous atmosphere considerations that shape the electrical design, and what SCADA needs from the headworks.
10 min readUpdated Sep 5, 2026
Clarifier Control
Primary and secondary clarifiers from the control room: the mechanism drive and its torque protection, sludge blanket measurement and sludge withdrawal control, scum removal, the weir and the effluent turbidity, and the sludge blanket as the early warning for a secondary process losing its footing.
9 min readUpdated Sep 5, 2026
RAS and WAS Control
Return and waste activated sludge: what each flow does for the process, RAS control by influent flow ratio or by blanket level, WAS control to a target sludge age or a target mixed liquor concentration, the flow and solids measurements each needs, and the pump and valve arrangements that make the setpoints achievable.
10 min readUpdated Sep 5, 2026
Raw Water
Controlling the front of a surface water plant: intake and screens, low-lift pumping, the raw water flow that paces the whole plant, the online quality instruments that warn of a changing source, and the alarms and ramp limits that keep the train stable.
9 min readUpdated Sep 5, 2026
Wells
Operating a wellfield as a water source: selecting and rotating wells, pump-to-waste on start, drawdown and specific capacity, wellhead chemical feed, blending for nitrate or arsenic, the telemetry a well needs, and the interlocks that protect the pump.
10 min readUpdated Sep 5, 2026
Aeration
Aeration in drinking water treatment: stripping carbon dioxide, hydrogen sulfide, radon, and volatile organics, and oxidizing iron and manganese ahead of filtration. The aerator types, what each needs from the control system, the pH shift, and the interlocks.
9 min readUpdated Sep 5, 2026
Filtration
Controlling gravity and pressure filters: effluent rate and level control, head loss and turbidity on every filter, the backwash triggers and sequence, filter-to-waste and ripening, the turbidity rules that filter monitoring answers to, and the operator view.
11 min readUpdated Sep 5, 2026
Chemical Feed
Chemical feed from the control side: the chemicals and where they go, metering pumps and dry feeders, flow pacing with residual trim, the dose arithmetic, day tanks and drawdown tests, loss-of-feed detection, interlocks, and overfeed protection.
11 min readUpdated Sep 5, 2026
Finished Water Storage
Storage inside the plant: the clearwell that provides contact time and high service suction, backwash supply tanks, and how their levels drive production and pumping. The contact time calculation and the minimum level it demands, water age, and alarms.
9 min readUpdated Sep 5, 2026
High Service Pumping
Pumping finished water into distribution: the control modes of tank level, pressure, and flow, how they interact with the clearwell and contact time, staging and surge, the telemetry the station depends on and its fallback, energy scheduling, and the alarms.
10 min readUpdated Sep 5, 2026
High Service Pumps
The pumps that carry finished water into distribution: types, the pump curve against the system curve, best efficiency point, the affinity laws and where a drive pays, parallel operation, valves, protection, and the efficiency monitoring that shows wear.
11 min readUpdated Sep 5, 2026
VFD Control for Water Pumping
Variable speed pumping and where it earns its cost: the affinity laws and how static head limits the savings, the minimum speed a pump can run, pressure, flow, and level control with a drive, and how to estimate the savings before buying.
9 min readUpdated Sep 5, 2026
Flow Control in Water Pumping
Controlling the flow a pumping system delivers: speed against valves, flow-paced pumping to a treatment rate, the flow loop with its ramp limits and its meter placement, and the loop tuning that keeps a flow controller steady.
8 min readUpdated Sep 5, 2026
Ground Storage Tanks
Controls for ground storage tanks: level measurement and its datum, filling from wells and treatment by pump control or altitude valve, and the telemetry that ties the tank to the system.
8 min readUpdated Sep 5, 2026
Pump Sequencing for Storage
Sequencing the pumps that fill and draw from storage: staging on level bands, rotating wells and sources for even use and water quality, time-of-day and demand-based scheduling, and the records that show the sequence is doing its job.
8 min readUpdated Sep 5, 2026
Reverse Osmosis
Reverse osmosis from the controls side: what the skid contains, the instruments that matter, the numbers an operator watches, recovery, rejection, normalized permeate flow, and the trends that say when the membranes need cleaning or replacement.
10 min readUpdated Sep 5, 2026
Nanofiltration
Nanofiltration from the controls side: how it differs from reverse osmosis in pressure, recovery, and what it removes, the softening and color removal applications where it dominates, and trends that are shared with reverse osmosis and the ones that differ.
8 min readUpdated Sep 5, 2026
Membrane Control
The control system of a membrane skid: the loops for permeate flow, recovery, and dosing, the permissives and trips, the start, run, flush, and shutdown sequences, and the data the operators and the membrane supplier need from the historian.
9 min readUpdated Sep 5, 2026
Clean-in-Place
Cleaning membranes in place: the triggers from the normalized trends, the low pH clean for scale and the high pH clean for organics and biofouling, the sequence of flush, heat, recirculate, soak, and rinse, and how automation makes cleaning repeatable.
9 min readUpdated Sep 5, 2026
Membrane Feed Pumps
The high-pressure feed pumps of a membrane plant: multistage centrifugal pumps on drives, the pressure ramp that protects the elements, suction protection and the cartridge filters ahead of them, and the maintenance that the trends point to.
8 min readUpdated Sep 5, 2026
Concentrate Systems
Handling the concentrate a membrane plant produces: the concentrate valve and the recovery it sets, flow and quality monitoring for the permit, the disposal routes, surface discharge, sewer, and the alarms and records a concentrate permit expects.
8 min readUpdated Sep 5, 2026
Lift Station SCADA
Getting a remote station onto the SCADA system and keeping it there: which signals to bring back and which controls to allow, the telemetry path from licensed radio to cellular to fiber, and the maintenance that keeps the link up.
9 min readUpdated Sep 5, 2026
Biological Treatment
The biological process from the controls side: activated sludge and its common forms, conventional, extended aeration, oxidation ditch, sequencing batch reactor, and membrane bioreactor, and the alarms that give an operator time.
9 min readUpdated Sep 5, 2026
Chemical Systems in Wastewater Treatment
The chemical feeds of a wastewater plant and their controls: coagulants for phosphorus, polymer for thickening and dewatering, hypochlorite and sulfite for disinfection and dechlorination, and the alarms that keep the plant in its permit.
9 min readUpdated Sep 5, 2026
Effluent Disinfection
Disinfecting the effluent and proving it: chlorination with contact time and residual control, dechlorination with sulfite controlled by ORP or a residual analyzer, ultraviolet systems with dose control from flow, and the records the discharge report needs.
9 min readUpdated Sep 5, 2026
Effluent
Effluent from the controls side: the flow measurement the permit is built on, the composite samplers it paces, the parameters measured online, flow, pH, dissolved oxygen, residual, turbidity, and the data integrity that makes the record defensible.
8 min readUpdated Sep 5, 2026
Residuals
Solids handling from the controls side: thickening by gravity, flotation, or drum, aerobic and anaerobic digestion with their temperature, mixing, and gas systems, dewatering by belt press, centrifuge, and the records that biosolids regulation requires.
9 min readUpdated Sep 5, 2026
Constant Speed Pump Control
On and off pumping with constant speed pumps: why it remains the right answer at most lift stations, the level bands and the wet well volume that set the cycle, starts per hour and motor limits, and the cases where variable speed is worth its cost.
8 min readUpdated Sep 5, 2026
Station Flow Control
Controlling the flow a lift station sends downstream: why a station would limit or match its flow, the plant hydraulic limit, the force main capacity, equalization, and wet weather, and the alarms.
8 min readUpdated Sep 5, 2026
Pump Sequencing Strategies
The strategies for sequencing wastewater pumps: level bands with alternation, lead and lag and standby with runtime balancing, a drive lead with constant speed lag, pump-down against steady-flow operation, and how each strategy fails and recovers.
9 min readUpdated Sep 5, 2026
IEC 62443
The international standard series for industrial automation and control system security: how it is organized, what security levels and foundational requirements mean, and how a utility or integrator actually uses it.
11 min readUpdated Sep 5, 2026
Zones and Conduits
The IEC 62443 way to segment a control system: grouping assets into zones with a shared security level, inventorying every conduit between them, and turning the drawing into firewall rules. With a worked water utility example.
12 min readUpdated Sep 5, 2026
Vendor Remote Access
Integrators and equipment vendors need to get in. How to let them without leaving a permanent door open: utility-controlled sessions, named accounts, MFA, a jump host, session recording, and what to do about the modem you did not know was there.
11 min readUpdated Sep 5, 2026
Controller Hardening
What can be locked down on a PLC or RTU: keyswitch and mode, credentials, unused services, access lists, firmware, and the engineering workstation that is the real target.
12 min readUpdated Sep 5, 2026
Industrial DMZ Design
The buffer zone between the business network and the control system: what goes in it, the no-direct-path rule, push-not-pull data flows, the firewall pair, and the services a utility actually needs to place there.
10 min readUpdated Sep 5, 2026
Jump Hosts
The one machine every remote session must pass through: what a jump host is, how it is hardened, what it may reach, session recording, the tools it carries, and why a vendor laptop never gets past it.
9 min readUpdated Sep 5, 2026
PLC Program Backups
What a complete controller backup contains, how often to take one, where to keep it, why the upload from the running controller is not the master, and the verification that turns a folder of files into a recovery plan.
9 min readUpdated Sep 5, 2026
Default Credentials
The passwords printed in the manual: where they hide in a control system, why they are the first thing an attacker tries, how to find every one on site, and the procedure for changing them without locking yourself out.
8 min readUpdated Sep 5, 2026
Small Utility Cybersecurity Priorities
What a utility with a few operators and no IT department should do first: the ten measures that remove most of the risk for the least money and time, in the order to do them, with what each one costs, what it prevents, and how to know it is done.
10 min readUpdated Sep 5, 2026
OT Risk Assessment
Ranking what could go wrong in a control system and what it would cost: the consequence-first method for utilities, the assets and scenarios to list, likelihood without pretending to know it, the risk matrix, and turning the ranked list into a work plan.
10 min readUpdated Sep 5, 2026
What to Back Up in a Control System
What a utility must be able to restore after a failure or attack: controller programs and firmware, SCADA and historian, HMI panels, drive and instrument parameters, network configurations, licenses, installers, and documentation, and how often each changes.
10 min readUpdated Sep 5, 2026
OT Incident Response Plan
The plan for the day the control system is not trusted: who decides, the triggers, the first hour, isolating without stopping treatment, running by hand, preserving evidence, who to notify and when, recovery from backups, and the exercise that makes it real.
10 min readUpdated Sep 5, 2026
Industrial Firewalls
Firewalls built for control networks: how they differ from office firewalls, where they belong in a utility network, transparent versus routed modes, Modbus and DNP3 awareness, logging, and the ruggedized units that protect one controller or a remote site.
9 min readUpdated Sep 5, 2026
Firewall Rule Design
Writing the rule set for a control network boundary: default deny, one rule per conduit with its reason, hosts not subnets, protocol and port and function, direction and initiator, logging on every rule, and the review that removes forgotten rules.
9 min readUpdated Sep 5, 2026
Controller Mode Switch and Keyswitch
The physical switch on the front of a controller: what RUN, REMOTE, and PROGRAM mean, why most controllers are left in REMOTE and why that matters, a policy for a utility, how mode is monitored and alarmed, and what to do on platforms with no keyswitch.
8 min readUpdated Sep 5, 2026
Controller Program Integrity
Knowing that the program in the controller is the one that was approved: checksums and change counters, the scheduled compare against the trusted backup, signed and protected projects, what an unexplained difference means, and making the check routine.
8 min readUpdated Sep 5, 2026
Server Hardening
Reducing what an attacker can do with a SCADA server: a baseline from the vendor guide and a benchmark, unused services removed, the host firewall on, application allowlisting, controlled media, separate administrator accounts, and logs sent off the box.
10 min readUpdated Sep 5, 2026
User Accounts and Roles
Who can do what on the SCADA and how it is enforced: roles from view-only to administrator and their permission matrix, individual accounts including the operator console, service and vendor accounts, same-day offboarding, and the quarterly review.
9 min readUpdated Sep 5, 2026
Patch Management
Applying updates to SCADA servers and clients without breaking the plant: vendor qualification, a monthly cycle with a test system, priority from the exposed edge inward, backups and rollback, emergency patches, and handling software that cannot be patched.
9 min readUpdated Sep 5, 2026
Historian Security
The historian is the most connected server in a control system and the most exposed: giving the office, reports, and the cloud the data they need without a path to the plant, with a collector in the control zone, a replica in the DMZ, and one-way flow.
9 min readUpdated Sep 5, 2026
Third-Party Software
Everything on a control system machine that is not the SCADA: drivers, databases, runtimes, reporting tools, agents, remote support utilities. Why each is an attack surface, the inventory and approved list, rules for installs, and removing what is unused.
8 min readUpdated Sep 5, 2026
Shared Account Problems
Why the shared operator login, the vendor account everyone knows, and the single PLC password are the weakest point in most utilities: no accountability, no offboarding, no detection. Containing what cannot be avoided and migrating the rest.
8 min readUpdated Sep 5, 2026
Password Policy for OT
A password policy that fits a control system rather than an office: length over complexity, rotation on events, screening against breached lists, multi-factor authentication, no lockouts that take control from an operator, and unique vaulted device passwords.
8 min readUpdated Sep 5, 2026
Credential Storage
Where the passwords and keys of a control system are kept: a vault with individual access and a log, break-glass copies in a safe, platform credential stores for service accounts, and the places they must not be, from spreadsheets to project files.
8 min readUpdated Sep 5, 2026
Security Program Basics
What a control system security program is for a utility that has never had one: a named owner, an inventory, a risk assessment, a few policies, baseline controls, training, vendor rules, an exercised incident plan, and a first-year plan for a small staff.
10 min readUpdated Sep 5, 2026
SCADA Backups
What a SCADA backup must contain to bring a system back: the project export, an image of each server, the databases, historian archives, licenses, certificates, scripts, and network device configurations, with frequency, retention, and the restore procedure.
9 min readUpdated Sep 5, 2026
Backup Testing
Why backups that have never been restored fail when needed, and how to find out: spot restores, full restores of a server to an isolated machine, controller program restores to a spare, archive reads, timing each one, and the findings and record that follow.
8 min readUpdated Sep 5, 2026
Offline Copies
The backup copy that survives ransomware: why anything reachable over the network will be encrypted too, what offline and immutable mean, options from rotated drives to immutable storage, what goes in the offline set, and the restore test that uses it.
8 min readUpdated Sep 5, 2026
Configuration Baselines
A known-good record of how every part of the control system is configured, captured at acceptance and kept current through change management: what to baseline, how to capture and store it, how to compare on a schedule, and what an unexplained difference means.
8 min readUpdated Sep 5, 2026
Program Change Detection
Knowing when a controller program changed and whether it was supposed to: change counters and signatures the SCADA can alarm on, scheduled compares, audit logs, mode and network monitoring, what each catches, and what to do when one fires.
9 min readUpdated Sep 5, 2026
Change Management for OT
A change process sized for a utility control system: what counts as a change, the request with risk and rollback, owner approval, the window, backup before and verification after, the baseline update, the emergency path, and the record.
9 min readUpdated Sep 5, 2026
Isolating a Compromised System
Cutting a compromised machine, segment, or site off from the control system without stopping the process: who may decide, isolation points planned in advance, disconnecting the network rather than the power, running on manual control, and preserving evidence.
9 min readUpdated Sep 5, 2026
Manual Operation Procedures
Written procedures for running the plant and the remote sites without the SCADA or the controllers: what to read and set by hand, how often to check, what to log, chemical dosing from a flow reading, when to stop, staffing, and the drill that proves them.
9 min readUpdated Sep 5, 2026
Recovery and Restoration
Bringing a control system back after a compromise without reintroducing it: controllers verified against baselines first, servers rebuilt from clean media and project exports, every credential changed, hardening, staged reconnection, and end-to-end tests.
9 min readUpdated Sep 5, 2026
Reporting Requirements
Who a water or wastewater utility must tell about a cyber incident, how fast, and what to say: the federal critical infrastructure reporting rule, state laws, the drinking water regulator, public notification, law enforcement, the sector center, and insurers.
9 min readUpdated Sep 5, 2026
Building an OT Asset Inventory
The list of everything in the control system with a network interface or a program, and how to build one that is right: what counts, the fields to record, the site walk, the switch tables and passive listening that find the rest, and keeping it current.
9 min readUpdated Sep 5, 2026
Passive Discovery
Finding out what is on a control network by listening rather than probing: why active scans are risky around older controllers, how a mirror port feeds a sensor, what the traffic reveals, the blind spots, and how the sensor becomes continuous monitoring.
8 min readUpdated Sep 5, 2026
Documenting Firmware Versions
Why the firmware version of every controller, module, drive, switch, radio, and instrument belongs in the inventory with the date it was read: advisories are issued by version. Where to read each one, the several versions one controller has, and the cadence.
8 min readUpdated Sep 5, 2026
Advisories and Alerts
Where a utility learns its equipment has a known vulnerability and what to do with the news: the government and vendor advisory feeds, the sector center, the exploited catalog, subscribing by product, a weekly triage on exposure and consequence, and records.
8 min readUpdated Sep 5, 2026
Risk-Based Patching
Deciding what to patch first when everything cannot be patched at once: priority from exposure, exploitation, and consequence rather than scores, tiers with timelines, different rules for servers, network gear, and controllers, and the written accept decision.
8 min readUpdated Sep 5, 2026
Compensating Controls
What to do about a vulnerability that cannot be patched now or ever: restricting who can reach it, disabling the service, blocking dangerous protocol functions, allowlisting, monitoring, physical and procedural controls, matched to the attack path.
8 min readUpdated Sep 5, 2026
AWIA Requirements
What the 2018 water infrastructure act requires of community water systems: a risk and resilience assessment and an emergency response plan, certified on a schedule by size and repeated every five years, with cybersecurity named in both, and who is covered.
9 min readUpdated Sep 5, 2026
EPA Guidance
What the federal environmental agency provides to water and wastewater utilities on cybersecurity and what it expects: the free assessment, the checklist aligned with federal goals, joint incident response guidance, the enforcement position, and how to use it.
8 min readUpdated Sep 5, 2026
CISA Resources
What the federal cybersecurity agency provides to utilities without charge: the performance goals, regional advisors, external vulnerability scanning, control system advisories, the exploited catalog, a self-assessment tool, exercises, and incident reporting.
8 min readUpdated Sep 5, 2026
VLAN Segmentation
Using VLANs to build the zones of a control network on shared switches: what a VLAN separates and what it does not, the zone-to-VLAN mapping, trunks and the native VLAN, routing only through a firewall, and where separate hardware begins.
9 min readUpdated Sep 5, 2026
Data Diodes
Hardware that lets data flow one way only, from the control network outward, with no physical return path: what a data diode and a unidirectional gateway are, where they belong, what they can and cannot carry, and when a firewall is enough instead.
8 min readUpdated Sep 5, 2026
Segmenting a Remote Site
A lift station, a well, or a tank site as its own zone: the site firewall and what it permits, the modem as transport with no public address, cameras and extras off the control segment, engineering access through the plant, and local control without the link.
9 min readUpdated Sep 5, 2026
VPN Design
How a VPN fits remote access for a control system: it terminates in the DMZ and lands on a jump host, never the control network; site-to-site tunnels carry telemetry; user tunnels require multi-factor and individual accounts; the concentrator is patched fast.
9 min readUpdated Sep 5, 2026
Multi-Factor Authentication
Requiring a second proof of identity beyond a password, where it matters most in a control system and how to do it without locking an operator out: the factor types, where it is mandatory, where it does not fit, enrollment and recovery, and vendor accounts.
8 min readUpdated Sep 5, 2026
Session Logging
Recording every remote session into the control system: who connected, from where, when, to what, and what they did, from the VPN log through jump host session recording to the SCADA audit trail and controller change log, stored off the systems and reviewed.
8 min readUpdated Sep 5, 2026
Deep Packet Inspection
What a firewall can do when it understands the control protocols: allowing reads and blocking writes, permitting programming only from one workstation in a window, rejecting malformed messages, and alerting on function codes that should never appear.
8 min readUpdated Sep 5, 2026
Firewall Logging and Review
Making the firewall log useful: logging on every rule including sensitive permits, sending logs to a collector off the firewall, what denials and unexpected permits mean, a weekly review a small utility can sustain, and the alerts worth waking someone for.
8 min readUpdated Sep 5, 2026
Firmware Management
Updating the firmware of controllers, modules, drives, HMIs, switches, and radios without breaking the plant: why firmware lags and why it still matters, tracking versions, deciding what to update and when, and the update as a planned outage with a rollback.
9 min readUpdated Sep 5, 2026
Disabling Unused Services
Every service a device runs is a way in, and most ship with more running than the plant uses: web servers, file transfer, shells, discovery, management protocols, unused ports. Finding what is listening, deciding what the plant needs, and turning off the rest.
8 min readUpdated Sep 5, 2026
How to Create a PID Loop in a PLC
Set up a PID instruction from scratch: scale the PV and CV, pick the action, set the execution rate, configure limits and anti-windup, tune conservatively, and test the manual and auto transitions before it controls anything.
10 min readUpdated Sep 5, 2026
How to Add an Alarm
From a request to a working alarm: define it against the philosophy, build the condition in the PLC with deadband and delays, configure the SCADA alarm with priority and message, test it end to end, and record it in the master alarm database.
9 min readUpdated Sep 5, 2026
How to Calibrate a Pressure Transmitter
A five-point calibration with a pressure source and a reference: isolate and vent, record as-found, decide whether to adjust, trim the sensor and the output separately, verify as-left, and record it so the next calibration means something.
9 min readUpdated Sep 5, 2026
How to Diagnose a Ground Loop
Prove that a noisy or offset analog signal is a ground loop, find the second ground, and fix it the right way: remove the extra ground, isolate the signal, or correct the shield termination. With the measurements that make the diagnosis certain.
9 min readUpdated Sep 5, 2026
How to Configure a Modbus Connection
Set up a Modbus RTU or TCP link between a controller and a device: get the register map, match the physical and protocol settings, build the reads and writes, handle data types and the addressing offset, and verify with a protocol tool before trusting a value.
10 min readUpdated Sep 5, 2026
How to Diagnose a Bad Quality Tag
Trace a bad quality indication from the SCADA screen back to its source: the tag configuration, the driver and device connection, the controller tag, and the field signal, using the diagnostics each layer provides, and separate a stale value from a bad one.
8 min readUpdated Sep 5, 2026
How to Calculate a Panel SCCR
Determine the short-circuit current rating of a control panel by the UL 508A Supplement SB method: list every power circuit component, find each rating, apply published series combinations and current limiting, and mark the panel with the lowest result.
10 min readUpdated Sep 5, 2026
How to Configure a Radar Level Transmitter
Commission a non-contact radar on a wet well or tank: mount it, set the reference and range from measured elevations, map false echoes with the vessel empty, set damping and the output, and verify against a tape at two levels before the controller uses it.
9 min readUpdated Sep 5, 2026
How to Assign IP Addresses on a Control Network
Build an addressing plan before the first device is configured: one subnet per zone and site, a fixed block layout so an address says what the device is, static addresses on everything that controls a process, and a schedule that is kept current.
9 min readUpdated Sep 5, 2026
How to Configure VLANs on a Control Network
Turn a zone plan into switch configuration: a VLAN per zone with its own subnet, access ports for devices, tagged trunks between switches, a native VLAN that carries nothing, a separate management VLAN, and routing between VLANs only through the firewall.
10 min readUpdated Sep 5, 2026
How to Troubleshoot an Ethernet Connection
Work an Ethernet problem one layer at a time: link light and cable, then speed, duplex, and VLAN on the switch port, then address, mask, and gateway, then the application port through the firewall. Each layer has a one-minute test that rules it in or out.
10 min readUpdated Sep 5, 2026
How to Diagnose Packet Loss
Find where and why frames are dropped: measure loss with a continuous ping, localize it hop by hop from both directions, read the port counters on the path, and match the pattern to its cause: a cable, a duplex mismatch, congestion, a loop, or a radio link.
10 min readUpdated Sep 5, 2026
How to Build a Sequencer
Build a step sequencer in a controller that will not stick, restart into the wrong step, or leave equipment half way: define the steps from the narrative, choose a step register, and test every path before the plant depends on it.
9 min readUpdated Sep 5, 2026
How to Diagnose Read and Write Communications
Diagnose a controller that cannot read from or write to a device: capture the exact request and response, classify the failure as no link, no answer, or a rejected exchange, read the error or exception code, compare with a test tool, and fix the port.
8 min readUpdated Sep 5, 2026
How to Configure Remote I/O
Add a remote I/O rack to a controller over Ethernet: plan the network and addresses, set the adapter, and prove every point and the failure behavior before the rack goes into service.
8 min readUpdated Sep 5, 2026
How to Build a Tag
Create a SCADA tag that is correct, documented, and consistent with every other tag: name it by the convention, bind it to the right controller address or name, and verify it against the live value and the I/O list before it goes on a screen.
7 min readUpdated Sep 5, 2026
How to Configure Alarms
Configure alarms in the SCADA system from the alarm list: set the source, controller-generated or evaluated in SCADA, the limits and deadband and delay, and the notification; then test each alarm end to end and review the alarm rate after the first weeks.
8 min readUpdated Sep 5, 2026
How to Trend Data
Build trends that operators use: choose the tags that tell one story per trend, set scales and time spans that show the behavior, and make ad hoc trending fast enough that an operator reaches for it before a phone call.
7 min readUpdated Sep 5, 2026
How to Configure a Historian
Set up a process historian that collects what matters and keeps it: decide the tags and their classes, set collection intervals and deadbands per class, size the storage and the retention, and hand the operators a working trend on day one.
8 min readUpdated Sep 5, 2026
How to Build Pump Graphics
Build a pump symbol and faceplate that operators can read at a glance and use without error: a symbol that shows state by shape and a muted palette with color reserved for abnormal, and a test against the high-performance HMI principles before it is deployed.
8 min readUpdated Sep 5, 2026
How to Configure Remote Access
Give operators and engineers a way into the SCADA system from outside that does not give it to anyone else: a virtual private network with multi-factor authentication terminating in a demilitarized zone, and a test that proves the path works and that the.
8 min readUpdated Sep 5, 2026
How to Troubleshoot a Flowmeter
Work a flowmeter that reads wrong, reads zero, or reads with the pipe still: confirm the pipe is full and the flow is real, check the installation against the meter requirements, and compare against an independent measurement before adjusting anything.
9 min readUpdated Sep 5, 2026
How to Select Surge Protection
Select the surge protective devices for a control panel and its field circuits: list every conductor that enters, classify its exposure, choose the device type and ratings for the power, the loops, and write it into the drawings and the I/O list.
8 min readUpdated Sep 5, 2026
How to Size an Enclosure
Size a control panel enclosure so that everything fits, cools, and can be worked on: lay out the components with their clearances and wireway, add the spare space the plant will need, and mounting before ordering.
8 min readUpdated Sep 5, 2026
How to Build Terminal Schedules
Produce the terminal schedule that lets a technician find any wire: define the strips and their numbering, list every terminal with its wire numbers, the device and the field destination, and keep it current through every change.
7 min readUpdated Sep 5, 2026
How to Design Panel Grounding
Design the grounding and bonding of a control panel and its site so that faults clear, signals are clean, and surges have a path: bond the enclosure and everything in it, and verify with measurements before the panel is energized.
8 min readUpdated Sep 5, 2026
How to Test Fiber
Test a fiber link at acceptance and at fault: inspect and clean every connector, measure end-to-end loss with a light source and power meter in both directions and at the operating wavelengths, and record everything with the fiber schedule.
8 min readUpdated Sep 5, 2026
Processor Faulted
A PLC with its fault light on and no logic running. How to read what it is telling you, the causes in order of likelihood, and how to restart it without repeating the fault.
8 min readUpdated Sep 5, 2026
Outputs Not Energizing
The program says the output is on and the equipment is not running. Where the signal gets lost between the output image and the field device, and how to find the point in a few measurements.
8 min readUpdated Sep 5, 2026
Inputs Not Reading
A switch closes in the field and the program never sees it. How the wetting voltage, the common, sinking and sourcing, and the wiring each lose the signal, and how to find which one did.
8 min readUpdated Sep 5, 2026
Program Will Not Download
The software refuses to download, or the download starts and fails. The version, path, mode, memory, and protection problems behind it, and the order to check them in.
7 min readUpdated Sep 5, 2026
Logic Not Executing As Expected
The rung looks right and the plant does something else. The scan-order, duplicate-output, unscheduled-routine, and data-type traps behind it, and how to find which one you are in.
8 min readUpdated Sep 5, 2026
Retentive Data Lost
The plant came back from a power cycle with zero setpoints, zero totals, and the wrong pump as lead. Which backup failed, which restore overwrote what, and how to get the data back and keep it.
7 min readUpdated Sep 5, 2026
Values Frozen On Screen
The HMI shows numbers that are not changing while the plant runs. Whether the controller, the communication driver, the tag server, or the display stopped, and the order to check them in.
7 min readUpdated Sep 5, 2026
Tag Shows Bad Quality
A tag flagged bad or uncertain by the driver. What the quality codes mean, the difference between a device that is not answering and an address that does not exist, and how to clear each.
7 min readUpdated Sep 5, 2026
Pump Will Not Start
A pump that is called and does nothing. The order to check: permissives and mode, control power, the starter or drive, the motor circuit, and the pump itself, with the measurements that settle each one in minutes.
10 min readUpdated Sep 5, 2026
Pump Runs But No Flow
The motor turns and nothing moves. How to tell a clogged impeller from an air-bound pump, a closed valve, a stuck check, a broken coupling, or reverse rotation, using motor current and discharge pressure before pulling anything.
10 min readUpdated Sep 5, 2026
Pump Short Cycles
A pump that starts and stops far more often than it should: the control band, the level signal, a leaking check valve, a waterlogged pressure tank, a lag pump doing the lead job, and the starts-per-hour limit that makes short cycling a motor killer.
9 min readUpdated Sep 5, 2026
Drive Will Not Start in AUTO
The drive runs from the keypad or in HAND but not from the controller. The command source, the enable and safe torque off inputs, the speed reference, and the network control word, checked in the order that finds the problem fastest.
9 min readUpdated Sep 5, 2026
Transmitter Reads Wrong Value
The reading is steady, plausible, and wrong. How to prove it against a reference, then separate a scaling mismatch, a range change, a zero shift, an installation effect, and a genuine transmitter fault, with the order of checks that finds it fastest.
9 min readUpdated Sep 5, 2026
Level Reading Jumps
A level that steps, spikes, or flips to a fixed value while the water moves smoothly: the false echoes, foam, turbulence, condensation, cable faults, and controller-side causes behind each pattern, and how to tell them apart from the trend before opening a hatch.
9 min readUpdated Sep 5, 2026
Device Times Out
A polled device that answers late or not at all: how to read the driver counters, tell a dead device from a slow one, and find the timeout setting, the bus loading, the radio latency, the duplicate address, or the device that is simply too busy to answer.
9 min readUpdated Sep 5, 2026
Alarms Not Annunciating
The condition is real and nothing happened on the screen or the phone: where an alarm can be lost between the controller and the operator, from the alarm bit and the tag quality to the alarm server, the display filter, the shelved and suppressed lists, the audible, and the notifier.
9 min readUpdated Sep 5, 2026
Drive Faults on Overcurrent
An overcurrent trip on a variable frequency drive: what the drive measured and when, the difference between a trip at start, during acceleration, at steady speed, and at deceleration, the motor and cable faults behind each, the parameter settings that cause nuisance trips, and the tests that separate them.
9 min readUpdated Sep 5, 2026
Drive Faults on Overvoltage
A DC bus overvoltage trip on a drive: where the bus voltage comes from, why deceleration and a driving load raise it, the utility-side causes from a high supply and capacitor switching, the deceleration ramp and overvoltage controller settings, braking resistors, and how to tell a regeneration trip from a supply transient.
9 min readUpdated Sep 5, 2026
Motor Will Not Reach Speed
A drive that runs but never gets the motor to the commanded speed: the reference and its scaling, the maximum frequency and speed limits, current limit holding the ramp, a load beyond the motor, a wrong motor parameter set, and a low supply, with the drive readouts that separate them.
9 min readUpdated Sep 5, 2026
Drive Trips on Ground Fault
A ground fault trip on a variable frequency drive: how the drive detects it, the motor and cable insulation faults behind most trips, the submersible cable problem, the capacitive leakage on long cables and filters that produces nuisance trips, wiring errors, and the insulation test that decides it.
9 min readUpdated Sep 5, 2026
Ground Loop Symptoms
How a ground loop shows itself: hum on analog signals, offsets that change when large loads switch, serial links that error, and readings that differ by location. The mechanism, the measurements that prove it, and fixes that never lift a safety ground.
9 min readUpdated Sep 5, 2026
Floating Reference Between Panels
Signals between two panels that misbehave because the panels do not share a DC reference: inputs that never turn on or half turn on, strange voltages to ground, and noise that comes and goes. How DC commons should be bonded and how to cross a panel boundary.
9 min readUpdated Sep 5, 2026
Shield Grounded at Both Ends
A shield connected to ground at the panel and again in the field becomes a conductor between two grounds, and its current becomes noise on the pair inside. How to find the second connection, what to measure before lifting it, and when both ends are correct.
8 min readUpdated Sep 5, 2026
Missing Equipment Ground
An enclosure, motor, or device with no effective equipment ground: how it shows up as a tingle, a fault that does not trip, surge protection that does nothing, or instrument noise; how to test the path safely; and why a ground rod is no substitute.
9 min readUpdated Sep 5, 2026
High Neutral-to-Ground Voltage
What a neutral-to-ground voltage reading means, the values that are normal, and the causes of a high one: a long or heavily loaded neutral, harmonic current, a loose or open neutral, a missing service bond, or an extra bond downstream, and telling them apart.
9 min readUpdated Sep 5, 2026
Cable Routing Problems
Noise that comes from where a cable runs: signal cables sharing a conduit, tray, or wireway with power or drive cables, long parallel runs, and shallow crossings. How coupling works, the separations that prevent it, and how to find the shared path.
9 min readUpdated Sep 5, 2026
Common-Mode Noise
Noise that rides on both conductors of a signal pair together, relative to ground: where it comes from, why a differential input rejects it only up to a limit, how to tell it from normal-mode noise with a scope, and the fixes that work.
9 min readUpdated Sep 5, 2026
Radio Frequency Interference
Readings that jump when a handheld radio is keyed, inputs that flicker near a telemetry antenna, transmitters that drift beside a modem: how radio energy gets into control circuits, how to prove it with the radio itself, and the fixes.
9 min readUpdated Sep 5, 2026
Unshielded Cable in a Noisy Run
The signal was run in plain conductors through a route full of power and drive cables, and now it is noisy. What unshielded cable cannot do, how to prove the cable is the problem before pulling a new one, and the options when replacing it is not possible.
9 min readUpdated Sep 5, 2026
VFD Noise on Analog Signals
Analog readings that jump or wander when a drive runs, and speed references that make a drive hunt: how the drive output couples into signal wiring, why the input turns kilohertz noise into a slow wander, the tests that pin it on the drive, and the fixes.
10 min readUpdated Sep 5, 2026
Drive Causes Instrument Noise
When many instruments became noisy after a drive was installed, the drive installation is the place to look: the checklist for motor cable, shielding, grounding, filters, and carrier frequency that decides how much noise a drive puts into the plant.
10 min readUpdated Sep 5, 2026
No Control Power in Panel
The panel is dead: no pilot lights, no controller, no HMI. The order of checks from the disconnect through the control transformer and its fuses, the control breaker, the emergency stop chain, and the DC supply, with the readings that locate the break.
8 min readUpdated Sep 5, 2026
Fuse Blows Repeatedly
A control fuse that opens again after replacement has a cause the replacement did not touch: a shorted coil, a ground fault in a wet field device, an overloaded circuit, the wrong fuse type for inrush, or an intermittent short. How the timing identifies it.
8 min readUpdated Sep 5, 2026
Relay Chatter
A relay or contactor that buzzes, cycles, or will not stay pulled in: low coil voltage from an overloaded supply or a sag, an AC coil with a dirty armature or broken shading ring, a solid-state output leaking, or an input bouncing at its threshold.
8 min readUpdated Sep 5, 2026
Ground Fault Present
The ground fault indicator is on, the monitor alarms, or a fuse opens when a field circuit is energized: how to find which conductor touches ground and where, by dividing the circuit with the monitor or an insulation tester, and where faults hide.
8 min readUpdated Sep 5, 2026
Panel Overheating
A panel that runs hot: drives tripping on temperature in the afternoon, controllers faulting in summer, components discolored, a fan that never stops. The causes from an undersized enclosure to a clogged filter, measuring the rise, and the fixes.
8 min readUpdated Sep 5, 2026
Nuisance Breaker Trips
A breaker that trips without a fault anyone can find: inrush against an instantaneous trip, a circuit loaded beyond its rating by additions, the wrong trip curve, a breaker weakened by heat, a loose terminal, or harmonics. Reading the curve.
8 min readUpdated Sep 5, 2026
Loss of Control Voltage
Control voltage that drops out for a moment and comes back, resetting controllers and dropping contactors: utility sags when a large load starts, a transfer switch operation, a loose neutral, or an overloaded control transformer. Catching it with a recorder.
8 min readUpdated Sep 5, 2026
Power Supply Failure
A 24 volt DC supply whose output is gone, low, cycling, or noisy: an overload that has put it into current limit, a supply killed by heat and age, input voltage out of range, or surge damage. One test tells an overloaded supply from a dead one.
8 min readUpdated Sep 5, 2026
UPS Not Carrying Load
The power failed and the controls went down anyway: a battery aged out or never connected, a UPS sitting in bypass since a fault, an overload, loads on the wrong receptacles, or a failed self-test nobody read. Finding out which, and testing properly.
8 min readUpdated Sep 5, 2026
Voltage Sag on Motor Start
Lights dim, contactors drop, and controllers reset every time the big pump starts: the starting current of an across-the-line motor pulling down a weak source. Measuring the sag, checking the source, and fixing it with a soft starter or ride-through.
8 min readUpdated Sep 5, 2026
Generator Transfer Problems
The generator started and something still went wrong: no transfer, controls reset during the gap, drives faulted, pumps ran backward, or the retransfer caused a second outage. The sequence and its timers, neutral and rotation, and the monthly test.
9 min readUpdated Sep 5, 2026
Pump Loses Prime
A suction-lift pump that runs without pumping, or pumps for a while and then stops: air leaking into the suction line, a foot valve that lets the line drain, a lift too high, a vortex or an aerated inflow, or a self-priming casing that lost its charge.
8 min readUpdated Sep 5, 2026
Seal Failure Alarm
The moisture probe in a submersible pump has tripped its relay: a seal that is leaking, or moisture in the cable, the junction box, or the probe circuit, a relay that does not match the pump, or a failed relay. What the alarm should do and what to check.
8 min readUpdated Sep 5, 2026
Both Pumps Running Constantly
A duplex station where lead and lag run together and never catch up: inflow beyond one pump, pumps that lost capacity to wear or rags, a force main partly blocked, a pump that runs but does not pump, a level stuck high, or bad setpoints. The drawdown test.
8 min readUpdated Sep 5, 2026
Valve Will Not Reach Position
A valve commanded to a position that stops short: an obstruction or a seat the actuator cannot push through, travel limits or a positioner span set wrong, a stem binding, an actuator undersized or out of air, or a command signal that does not span.
8 min readUpdated Sep 5, 2026
Valve Hunting
A modulating valve that never settles: a loop tuned too hard, a positioner gain too high, stiction producing a limit cycle, a noisy command or feedback, an oversized valve working near its seat, or two loops fighting. The manual test that separates them.
8 min readUpdated Sep 5, 2026
Valve Slow to Respond
A valve that takes far longer to move than it should: a pneumatic supply restricted or leaking; a positioner tuned slow; an electric actuator whose speed is fixed; a stem binding in cold or packing; or a rate-limited output. Measuring the stroke time.
8 min readUpdated Sep 5, 2026
Position Feedback Wrong
The HMI says one position and the valve is at another: a feedback potentiometer worn or miscalibrated, a linkage that slipped, scaling that does not match, a reversed signal, limits set wrong, or noise. Comparing indicator, feedback, and process.
8 min readUpdated Sep 5, 2026
Actuator Torque Fault
An electric actuator that trips on torque: at the seat because the seating mode or setting is wrong, in mid-travel because something is in the way or the stem binds, or under flow because the differential exceeds the sizing. The checks before a reset.
8 min readUpdated Sep 5, 2026
Remote Site Stops Communicating
One radio site silent while its neighbors answer: site power, the radio, antenna and coax after a storm, a reset configuration, the controller behind it, or a changed path. What the master diagnostics say before anyone drives, and the order of checks on site.
8 min readUpdated Sep 5, 2026
Intermittent Radio Path
A site that drops and returns by the hour, season, or weather: thin fade margin, foliage, a new obstruction, a loosened antenna, coax taking water, a corroding connector, interference, or a marginal supply. How to trend signal against time and weather.
8 min readUpdated Sep 5, 2026
High Retry Count
Polls that succeed on the second or third try: a weak or noisy path, interference, collisions from a second master, a timeout shorter than the radio turnaround, a data rate the path cannot carry, or a slow controller. Reading retry statistics per site.
8 min readUpdated Sep 5, 2026
Poor Signal Margin
A path with too little signal above receiver threshold to survive rain, leaves, and inversions: the link budget from transmitter to receiver, the Fresnel zone, and why the margin is smaller than the study said. How to compute, measure, and add to it.
9 min readUpdated Sep 5, 2026
Interference on Channel
Data lost on a strong-signal path: another system on the frequency, a nearby transmitter overloading the receiver, intermodulation on a shared tower, drive noise, or a stuck transmitter. How to measure the noise floor, find the source, and cure it.
8 min readUpdated Sep 5, 2026
Cellular Modem Will Not Register
A modem that never attaches to the network: a module not activated, provisioned, or suspended; unsupported bands or a network shutdown; no antenna or coverage; a wrong access point name; or a reset modem. Reading the registration state and asking the carrier.
8 min readUpdated Sep 5, 2026
Frequent Reconnects
A cellular site that connects, drops, and reconnects: a weak signal at the cell edge, tower handoffs, idle session teardown, a NAT timeout that needs a keepalive, a firmware fault, a sagging supply, or an antenna problem. Settings that keep sessions up.
8 min readUpdated Sep 5, 2026
Data Plan or APN Problems
A modem that registers but has no data, or runs out mid-month: a wrong or changed APN, a capped or throttled plan, a module on the wrong plan or network, a missing static address, or polling that uses more data than planned. Sizing a plan, cutting traffic.
8 min readUpdated Sep 5, 2026
VPN Tunnel Drops
The modem is up and the tunnel keeps dropping: a changing cellular address, keepalive longer than the carrier timeout, mismatched rekey lifetimes, an oversized MTU, a modem reconnecting under the tunnel, a full concentrator, or a clock or certificate fault.
9 min readUpdated Sep 5, 2026
Weak Cellular Signal
A modem at the edge of coverage: the signal readings that matter, an antenna inside a metal enclosure or vault, the wrong band, a damaged antenna or lossy coax, a tower or carrier change, and fixes from a mast antenna to a directional one or a new medium.
8 min readUpdated Sep 5, 2026
Fiber Link Down
A fiber link with no light: a cut or crushed cable, a failed or unseated transceiver, a reversed patch cord, a dirty connector, a disabled port, a mismatched module pair, or a dead media converter. Reading port state and optical power to find the break.
8 min readUpdated Sep 5, 2026
High Optical Loss
A link that is up but running near the receiver floor: the loss budget from transmitter to receiver and what ate it. Dirty connectors, bad splices, tight bends, a run too long for the module, or a wrong fiber type. Measuring the loss and getting margin back.
9 min readUpdated Sep 5, 2026
Intermittent Fiber Link
A fiber link that flaps: down for seconds and back, worse at night, in the cold, in wind, or when a door opens. No margin, a nearly seated connector, a failing or hot transceiver, a moving bend, water freezing in a splice case, or a port flapping on its own.
8 min readUpdated Sep 5, 2026
Wrong Fiber Type or Wavelength
A link that will not come up, or runs with high loss, because parts do not match: single-mode modules on multimode fiber, a multimode cord in a single-mode run, mixed grades, different wavelengths, or a same-wavelength bidirectional pair. Reading the markings.
8 min readUpdated Sep 5, 2026
Dirty or Damaged Connector
The most common fiber fault: a connector end face with dust, oil, or a scratch that takes decibels from the link and damages its mate. How to inspect with a scope, what contamination and damage look like, how to clean properly, and when to replace it.
8 min readUpdated Sep 5, 2026
Intermittent Packet Loss
Polls that occasionally fail, tags that flicker bad, a ping that drops one in fifty: a bad cable or port, a duplex mismatch, a saturated link, a buffer overrun, a marginal radio or fiber hop, a slow device, or a loop. Finding which hop loses packets and why.
9 min readUpdated Sep 5, 2026
Cannot Ping Across VLANs
Two devices that work on their own networks but cannot reach each other across a VLAN boundary: no route, a wrong or missing gateway, a mask that puts the target on the wrong side, a trunk missing the VLAN, or a firewall rule. Testing each in order.
8 min readUpdated Sep 5, 2026
Duplicate IP Address
Two devices claiming one address: a controller that answers sometimes, a workstation that reports a conflict, a ping returning from two hardware addresses. Where duplicates come from, finding both in the switch address table, and the discipline that stops it.
7 min readUpdated Sep 5, 2026
Switch Port Errors Incrementing
What each counter on a managed switch port means and which fault makes it grow: check errors from a damaged cable or noise, late collisions from a duplex mismatch, runts from a bad transceiver, discards from congestion, link flaps from a marginal connection.
9 min readUpdated Sep 5, 2026
Broadcast Storm
A network suddenly slow or dead everywhere, every link light solid: a loop between switches without protection, a failed ring protocol, or a device flooding broadcasts. Recognising a storm, breaking it with a cable pull, finding the loop, and preventing it.
8 min readUpdated Sep 5, 2026
Trend Gaps
Holes in a trend where data should be: a communication loss, a historian that stopped or fell behind, a buffer that filled or never forwarded, compression set too coarse, a renamed tag, or a clock that jumped. Reading the cause from the shape of the gap.
8 min readUpdated Sep 5, 2026
Client Cannot Connect
A workstation, web, or mobile client that cannot reach the SCADA server: the service down, a firewall path closed, a license or session limit, a certificate or name failure, a version mismatch after an update, or expired credentials. Testing each layer.
8 min readUpdated Sep 5, 2026
Duplicate or Missing History
A historian with two records for one moment, or none: a redundant pair both collecting, a buffer that forwarded twice, a tag under two names, a daylight saving shift, or a source that resends on reconnect. Cleaning the record without inventing data.
8 min readUpdated Sep 5, 2026
Signal Pegged High or Low
A 4-20 mA signal stuck at a rail or a fault current: a transmitter in fault, a process truly out of range, an open or shorted loop, a wrong range, a wiring error, an input channel fault, or a scaling clamp. How the current itself tells you which.
8 min readUpdated Sep 5, 2026
Analog Does Not Match Field Indicator
The gauge on the pipe says one thing and the screen says another: a scaling or range mismatch, a drifted transmitter, a drifted gauge, a different elevation or datum, different units, or damping that lags. Deciding which is right and where the error lives.
8 min readUpdated Sep 5, 2026
Loop Powers Up but Reads Zero
The transmitter is lit and the controller shows zero, so loop current is not reaching the input: a loop wired for power but not signal, an active and passive mismatch, a missing jumper, an unconfigured channel, a blown fuse, or a transmitter sending nothing.
7 min readUpdated Sep 5, 2026
Read Works but Write Fails
Polling a device returns good data and writing a setpoint does nothing or returns an exception: a write-protected device, a read-only register, the wrong function code, a wrong address or type, logic that overwrites the value, a security rule, or a local mode.
8 min readUpdated Sep 5, 2026
Wrong Register Data
The poll succeeds and the numbers are nonsense: an offset by one, the wrong table, swapped words in a 32-bit value, a float read as an integer, signed read as unsigned, a scale factor not applied, a stale gateway value, or the wrong unit answering.
8 min readUpdated Sep 5, 2026
Protocol Gateway Stops Passing Data
The gateway is powered and pingable and the data behind it is frozen or gone: the device side failed while the master side answers, a stalled gateway, configuration lost on a power cycle, a stale mapping, or a master polling too fast. Testing each side.
8 min readUpdated Sep 5, 2026
How to Read a P&ID
What a piping and instrumentation diagram shows, how ISA-5.1 tag bubbles and line types encode the control system, and how to trace a loop across sheets.
8 min readUpdated Sep 5, 2026
Control Narratives
What a control narrative is, what it must contain, how to write statements that can be tested, and how it drives programming, FAT, and the owner’s acceptance.
9 min readUpdated Sep 5, 2026
Sequences of Operation
Writing the ordered, step-by-step description of what a system does: states, transitions, timeouts, and the format that lets a programmer implement it and a tester verify it without interpretation.
8 min readUpdated Sep 5, 2026
Cause and Effect Matrices
The table that lists every trip condition against every action it causes: how to build one, what goes in the cells, how it distinguishes hardwired from software protection, and how it becomes the test.
7 min readUpdated Sep 5, 2026
Factory Acceptance Testing
Testing a control system before it leaves the shop: what must exist before the test, how the procedure is built from the narrative and the matrix, how the field is simulated, what is witnessed, and what the punch list and the sign-off mean.
9 min readUpdated Sep 5, 2026
Site Acceptance Testing
Proving the installed system with the real field: loop checks first, then end-to-end I/O, real communications, sequences on real equipment, alarms to real recipients, and failure modes on the real network, with the record that becomes the as-built.
8 min readUpdated Sep 5, 2026
I/O Lists
The document that ties the field to the controller: what every I/O list column means, how tags, terminals, and module channels are assigned, spare capacity rules, how the list drives the drawings and the program, and how to keep it true after commissioning.
9 min readUpdated Sep 5, 2026
Instrument Lists
The index of every measuring and final control device on a project: what the instrument list records, how it grows from the P&ID into specification sheets and calibration records, the columns that matter at each stage, and how it becomes the asset register the utility maintains.
8 min readUpdated Sep 5, 2026
Control Schematics
The ladder-style drawing of every control circuit in a panel: how a schematic is organized by line number, the conventions for contacts, coils, and cross-references, what belongs on a schematic and what belongs on a wiring diagram, and reading one under pressure.
9 min readUpdated Sep 5, 2026
Commissioning Checklist
From energization to handover: the sequence of commissioning activities for a control system, the prerequisites and records for each, who signs what, and the checklist that keeps a project from being declared finished while half of it has never been tested.
10 min readUpdated Sep 5, 2026
ISA Standards for Controls
The International Society of Automation standards a controls practitioner meets: ISA-5.1 symbols and tags, ISA-18.2 alarm management, ISA-101 HMI design, ISA-88 and ISA-95 for batch and enterprise integration, ISA-99 which became IEC 62443, ISA-20 specification forms, and how each is used on a water or wastewater project.
8 min readUpdated Sep 5, 2026
IEC Standards for Controls
The International Electrotechnical Commission standards a controls practitioner meets: IEC 61131 for programmable controllers and their languages, IEC 62443 for security, IEC 61511 for safety instrumented systems, IEC 60529 ingress protection ratings, the telemetry protocols, and how IEC and North American standards fit together.
8 min readUpdated Sep 5, 2026
NFPA Standards for Controls
The National Fire Protection Association documents that reach into a control system: NFPA 70, the National Electrical Code, and the articles that govern panels, motors, and instrumentation; NFPA 70E for electrical safety at work; NFPA 79 for industrial machinery; NFPA 820 for wastewater plant hazardous area classification; and NFPA 110 where standby power meets the controls.
9 min readUpdated Sep 5, 2026
UL Standards for Controls
The UL listings behind the components and the panels: UL 508A for industrial control panels and its SCCR supplement, UL 508 and UL 60947 for the components in them, UL 489 and UL 1077 for breakers and supplementary protectors, UL 248 fuse classes, UL 50 and 50E for enclosures, UL 698A for hazardous-location panels, and what a listing, a recognition, and a mark actually mean.
9 min readUpdated Sep 5, 2026
Wiring Diagrams
The drawing that says where every wire goes: panel wiring and interconnection diagrams, and the conventions of wire numbers, conductor colors, terminal numbers, and cable numbers that make them readable. What belongs here versus on the schematic.
9 min readUpdated Sep 5, 2026
Network Drawings
The two drawings every control network needs: a logical drawing of zones, subnets, VLANs, firewalls, and conduits, and a physical drawing of switches, ports, cables, fiber, radios, and sites. What each shows and why they are sensitive.
9 min readUpdated Sep 5, 2026
Panel Layouts
The drawing of what goes where inside a control panel: enclosure, back plate with every component to scale and keyed to the bill of material, wireways, terminals, door devices, and entries. The conventions, the required spacings, and the checks.
9 min readUpdated Sep 5, 2026
Cable Schedules
The list of every cable with what it is, where it runs, and where it lands: the columns, the numbering convention, types and signal classes, routes through conduits and trays, lengths, terminations, spares, and status from design through as-built.
8 min readUpdated Sep 5, 2026
Fiber Schedules
The record of every fiber strand between every pair of patch panels: cable identifiers, strand numbers and the standard color sequence, fiber type, connectors, what each strand carries, splices, lengths, and test results, with the labeling that matches it.
8 min readUpdated Sep 5, 2026
Network Schedules
The tables behind the network drawings: the address schedule of every device, the switch port schedule of every port, the VLAN table, and the conduit list of what the firewalls permit. How they are built, kept as the single source of truth, and protected.
8 min readUpdated Sep 5, 2026
Functional Descriptions
The system-level document that states what a control system does, organized from the overview down to each piece of equipment in one format: modes, control, setpoints, permissives, interlocks, alarms, sequences, and failure behavior, and how it is used.
10 min readUpdated Sep 5, 2026
Design Checklist
A review checklist for a control system design at each stage from concept to issued for construction: documents, architecture, controllers and I/O, panels and power, instruments, networks and security, SCADA and alarms, deliverables, and commissioning.
11 min readUpdated Sep 5, 2026
Startup Checklist
The checklist for bringing a control system and its process into operation after commissioning or an outage: verification of power, I/O, communications, setpoints, forces, and backups; staged energization; manual first, then automatic; and the watch.
8 min readUpdated Sep 5, 2026
Calibration Checklist
The checklist for one calibration event, from work order to the sticker on the instrument: notify operations, loop in manual, alarms inhibited, the reference standard, as-found, adjustment, as-left, the loop check, restoration, and the record.
8 min readUpdated Sep 5, 2026
Troubleshooting Checklist
A general checklist for any control system problem, usable at 2 a.m.: define the problem, ask what changed, make the process safe, gather the evidence before touching anything, divide the chain, change one thing at a time, restore, and record.
8 min readUpdated Sep 5, 2026
NIST Publications for Control Systems
The National Institute of Standards and Technology documents a control engineer will meet: the Cybersecurity Framework, the operational technology security guide, the control catalog, the digital identity guideline, and the incident handling guide.
9 min readUpdated Sep 5, 2026
CISA Guidance as a Reference
How the federal cybersecurity agency publications serve as reference standards for a utility: the performance goals as a baseline for policy and procurement, the water sector goals, secure-by-design principles for vendors, and the advisories.
8 min readUpdated Sep 5, 2026
EPA Rules and Their Control System Implications
The federal environmental agency rules that shape what a water or wastewater control system must measure, record, and report: the surface water rules, residual and byproduct rules, groundwater and lead rules, discharge permits, and record retention.
10 min readUpdated Sep 5, 2026
AWWA Standards and Manuals
What the American Water Works Association publishes that a control engineer uses: the instrumentation and control manual, the risk and resilience standard behind the act assessments, the security and emergency standards, and the cybersecurity tool.
8 min readUpdated Sep 5, 2026
Where the Logic Should Live: Controller, SCADA, or Relay
Every control decision has a home, and putting it in the wrong one is the root of most plants that are hard to operate. A rule for deciding what belongs in the controller, what belongs in SCADA, and what belongs in a relay.
9 min readUpdated Sep 5, 2026
What a Small Utility Should Ask Before Buying SCADA
A utility with a plant, a few dozen remote sites, and two operators on call is buying a system it will live with for twenty years. The questions that decide whether it works out, and they are not about features: licensing, staffing, and the exit.
9 min readUpdated Sep 5, 2026
The Tank Level Trend Tells the Whole Story
One trend, a storage tank level over a week, holds most of what an operator needs to know about a water system: demand, source capacity, leaks, pump health, water age, and why it deserves a permanent place on the main screen.
8 min readUpdated Sep 5, 2026
The Lift Station That Overflowed With Everything Working
A composite of overflows that happen at well-built stations: every pump ran, every alarm fired, every device did what it was designed to do, and the handful of changes that break the chain.
9 min readUpdated Sep 5, 2026
Calibration Is a Program, Not an Event
An instrument calibrated once at startup and again when someone complains is an instrument whose readings cannot be trusted in between. What a calibration program is, and how a small utility runs one without a full-time instrument technician.
8 min readUpdated Sep 5, 2026
The Panel You Can Troubleshoot at Two in the Morning
Panels are designed for the day they are built and used for the nights they fail. The design choices that decide whether a technician with a flashlight and a meter can find the fault: labels and wire numbers, and the fuse that tells you it blew.
8 min readUpdated Sep 5, 2026
Fiber Between Buildings, Every Time
The copper Ethernet cable between two buildings works on the day it is pulled and costs the plant a controller, a switch, and how to specify it so it stays simple.
7 min readUpdated Sep 5, 2026
The Cellular Router Is the Front Door
The most common way into a small utility control system is not a sophisticated attack on the plant firewall. It is a cellular router at a lift station with a public address and the password it shipped with. How these get installed, and the short list of.
8 min readUpdated Sep 5, 2026
Measure Before You Replace
Parts-swapping is the most expensive way to troubleshoot and the most common. A method for controls faults that starts with a measurement, splits the problem in half at every step, and ends with a cause instead of a coincidence.
8 min readUpdated Sep 5, 2026
The Control Narrative Is the Contract
Most control system disputes, delays, and disappointments trace to one missing document: a narrative that says, in plain language, and how it keeps paying after startup.
8 min readUpdated Sep 5, 2026
The Knowledge That Leaves With the Retiring Technician
Water and wastewater utilities are losing the people who know how their control systems actually work, and a practical program for capturing it while there is still someone to ask.
8 min readUpdated Sep 5, 2026
What Integrator Consolidation Means for a Small Utility
The regional controls integrator that built a utility system over twenty years is being bought, merged, or closed, and how to stop depending on any single firm for the system it owns.
7 min readUpdated Sep 5, 2026
The Backup That Would Not Restore
A controller failed on a Friday, the spare was on the shelf, and the saved program would not go in. What a PLC backup has to contain to actually put a system back, why the program file alone is not enough, and how a small utility keeps backups that work.
9 min readUpdated Sep 5, 2026
Alarms Nobody Answers
A SCADA system that raises eight hundred alarms a day has trained its operators to ignore it. How a small plant gets there, what the standing alarm list is telling you, and a one-day rationalization that gives the alarm system its voice back.
9 min readUpdated Sep 5, 2026
The Chlorine Residual Loop Is Slower Than You Think
Residual control loops oscillate because the measurement arrives minutes after the dose changes, and the tuning was done as if it arrived at once. Where the delay comes from, and how to control a loop whose dead time is longer than its response.
10 min readUpdated Sep 5, 2026
Inflow and Infiltration Shows Up in the Pump Runtime
Most small collection systems have no flow meters at the lift stations, but every station reports pump runtime and starts to SCADA. How to turn those two numbers into a station flow estimate, and rank where the money for pipe work should go.
9 min readUpdated Sep 5, 2026
When the Transmitter and the Gauge Disagree
The SCADA screen says 62 psi and the gauge on the pipe says 58, and someone has to decide which one to believe. Why two readings of the same pressure differ, and a procedure for settling the argument with a reference instead of an opinion.
9 min readUpdated Sep 5, 2026
Heat Kills Panels Slowly
Nothing in a control panel fails the day it gets hot. Power supplies, drives, relays, and the controller lose life a summer at a time, and what to do about it that actually works outdoors.
9 min readUpdated Sep 5, 2026
One Flat Network Is One Big Fault Domain
A looped patch cable in an office closet took down every PLC at the plant, because the office and the plant were one network. Why a flat network makes every fault a plant-wide fault, and how to get there one switch at a time.
9 min readUpdated Sep 5, 2026
The Vendor Laptop Is on Your Network Now
Every service call ends with a laptop plugged into the control network, and most utilities have no rule about it. What can go wrong when a vendor connects, and how to have the conversation without losing the vendor.
9 min readUpdated Sep 5, 2026
The Intermittent Fault Is a Data Problem
A fault that happens once a week at random cannot be found with a meter, because it is never happening while the meter is connected. How to turn an intermittent problem into a recorded one, and how the patterns in the record point at the cause.
9 min readUpdated Sep 5, 2026
As-Built Means Someone Walked the Panel
The drawings in the panel pocket are the ones from the bid set, and how a small utility keeps its drawings true after the integrator has gone.
9 min readUpdated Sep 5, 2026
Wet Well Level Control
The measurement that runs a lift station: choosing setpoints, protecting the pumps, validating the signal, and the failures that flood a station.
9 min readUpdated Aug 30, 2026
4-20 mA Current Loops
Why the industry standardized on current instead of voltage, how a two-wire loop is powered, what the live zero buys you, and how to read a loop with a meter.
12 min readUpdated Aug 29, 2026
Water and Wastewater Utility Threat Landscape
What has actually happened at water utilities, what those incidents had in common, and the small number of controls that would have prevented most of them.
8 min readUpdated Aug 28, 2026
Duplex Lift Station Controls
The two-pump station that makes up most of a collection system: what is in the panel, how the sequence works, what is monitored, and where these stations actually fail.
11 min readUpdated Aug 27, 2026
OT Security vs IT Security
Why the familiar security priorities invert on a plant floor, and what that changes about patching, scanning, authentication, and incident response.
8 min readUpdated Aug 26, 2026
UL 508A Industrial Control Panels
What the listing actually covers, what has to appear on the label, and the requirements that most often cause a panel to fail inspection.
9 min readUpdated Aug 25, 2026
How to Program Lead/Lag Pump Control
Build duplex pump control with alternation, failure detection, minimum run and off timers, and an operator override that survives a restart.
10 min readUpdated Aug 24, 2026
4-20 mA Signal Is Unstable
An analog reading that will not settle. How to separate a genuine process swing from induced noise, a ground loop, or a loop running out of voltage.
8 min readUpdated Aug 23, 2026
What Is a PLC?
A programmable logic controller is a ruggedized industrial computer that reads field inputs, solves a control program, and drives outputs on a repeating, deterministic cycle.
8 min readUpdated Aug 22, 2026
Modbus Device Intermittently Offline
A device that answers most of the time. Termination, bias, timing, and the physical layer details that produce a bus which almost works.
9 min readUpdated Aug 21, 2026
The Purdue Model
The reference architecture most segmentation designs still start from: what each level contains, where the DMZ goes, and how it maps to a water utility.
8 min readUpdated Aug 20, 2026
PID Control for Pumps and Valves
What each term actually does, how to tune a loop on a real pump station, and the handful of mistakes that cause most of the oscillation people blame on tuning.
11 min readUpdated Aug 19, 2026
Lead/Lag Pump Control
Which pump runs first, when the second joins, how they trade places, and the design decisions that determine whether a duplex station wears evenly.
9 min readUpdated Aug 18, 2026
Ethernet Device Drops Offline
An industrial Ethernet device that disappears and comes back. Duplex mismatch, cabling, spanning tree, and the switch counters that identify it in minutes.
9 min readUpdated Aug 16, 2026
ISA-18.2 Alarm Management
The lifecycle standard for alarm systems, the rate targets that define a workable system, and why alarm rationalization is the step nobody wants to fund.
10 min readUpdated Aug 15, 2026
How to Size a Control Panel Power Supply
Add up the real load, account for inrush and simultaneity, add headroom, and check the heat you just added to the enclosure.
7 min readUpdated Aug 14, 2026
How to Scale a 4-20 mA Input in a PLC
Turn raw analog counts into engineering units, verify at three points, and add the validity checks that stop a failed transmitter from producing a believable number.
7 min readUpdated Aug 12, 2026
Ladder Logic Fundamentals
Rungs, contacts, coils, and the relay conventions the language inherited — plus the patterns you will meet in almost every industrial program.
10 min readUpdated Aug 11, 2026
Ground Loops in Instrumentation
Two grounds at different potentials, one signal circuit between them, and a reading that will not sit still. How to find it and how to prevent it.
8 min readUpdated Aug 8, 2026
How to Test a 4-20 mA Loop
Prove a current loop end to end with a meter and a calibrator, without interrupting a process you were not authorized to interrupt.
8 min readUpdated Aug 6, 2026
What Is SCADA?
Supervisory control and data acquisition: the layer that collects data from controllers across a system, presents it to operators, records it, and lets them intervene.
9 min readUpdated Aug 4, 2026
Magnetic Flowmeters
Faraday's law applied to a pipe: how a mag meter works, the conductivity and full-pipe requirements, and why grounding decides whether it reads.
8 min readUpdated Aug 1, 2026
The PLC Scan Cycle
Read inputs, solve logic, write outputs, housekeeping. Understanding scan order explains most PLC behavior that looks wrong at first glance.
9 min readUpdated Jul 30, 2026
Modbus TCP
Modbus over Ethernet: what the MBAP header changes, why the CRC disappears, how the unit identifier works, and what does not get easier just because it is on Ethernet.
8 min readUpdated Jul 28, 2026
High Performance HMI Design
Grey backgrounds, reserved color, and displays designed to make abnormal conditions obvious rather than to look impressive in a demo.
8 min readUpdated Jul 24, 2026
Modbus RTU
Serial Modbus over RS-485: function codes, register addressing, the off-by-one that catches everyone, and the physical layer details that decide whether a bus is stable.
10 min readUpdated Jul 21, 2026
Analog Scaling: Raw Counts to Engineering Units
The arithmetic that turns an analog card reading into feet, psi, or gallons per minute — plus the range mismatches that silently corrupt it.
8 min readUpdated Jul 16, 2026
Radar Level Measurement
Non-contact and guided wave radar, why it handles a wet well better than most alternatives, and the installation details that decide whether it works.
9 min readUpdated Jul 9, 2026
Interlocks and Permissives
A permissive lets you start. An interlock stops you. Confusing the two produces equipment that either will not run or will not protect itself.
7 min readUpdated Jun 27, 2026
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Content on CurryControls.com is general technical reference information provided for educational and reference purposes only. It is not engineering advice for a specific installation. All information must be independently verified against current codes, standards, manufacturer documentation, project requirements, and qualified professional judgment before it is relied upon or applied.