Signals and PLC · Glossary

What is Signal Damping?

filter time constantSignals and PLC

Signal damping is a filter applied in a transmitter or PLC that smooths a noisy measurement by slowing its response.

Signal Damping Explained

Damping is set as a time constant in seconds. It hides turbulence and noise, but too much damping delays the signal, upsets control and slows trips.

Apply damping in one place, and keep it short for safety and fast control loops.

y_k = y_k−1 + (x_k − y_k−1) × T_s ÷ (τ + T_s)

x, y	raw input and filtered output
T_s	sample time
τ	filter time constant

Example: After one time constant the output reaches about 63 % of a step change.

What is Signal Damping?

Signal damping is a filter applied in a transmitter or PLC that smooths a noisy measurement by slowing its response.

How much damping should I use?

The smallest that gives a usable signal, often under 2 s for flow and pressure control.

Does damping affect trips?

Yes, it delays them; include it in the SIF response time.

Analog input stability: cable length problems

A practical guide on instrumentationblog.in with more detail on signal damping and how it is applied on real plants.

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