Topic
Grounding
26 guides across the knowledge base.
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
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
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
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
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
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
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
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 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 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
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
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
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
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
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
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
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
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
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
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