Controls › PLC Systems
Analog Control
Getting a field measurement into a controller and acting on it correctly.
Written guides in this section
Full references, procedures, and diagnostic guides published under Analog Control.
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
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
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
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
Topics in this area
4-20 mA
The two-wire current loop that carries most process measurements, why current beats voltage over distance, and how to read one with a meter.
Scaling
Converting a raw analog count into an engineering unit the operator can act on.
Raw Counts
What the analog-to-digital converter actually hands your program.
Engineering Units
Choosing and documenting the units a tag carries.
PID
Proportional, integral, and derivative control applied to pumps, valves, and pressure loops.
Filtering
Damping a noisy input without hiding a real process change.
Deadband
Preventing output chatter around a setpoint.
Signal Validation
Catching out-of-range, frozen, and failed analog inputs in logic.
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