Topic
Telemetry
26 guides across the knowledge base.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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