The derivative action of a PID controller can cause noise in the measured process variable (PV) to be amplified and reflected as “chatter” in the controller output (CO) signal. Signal filters, implemented as either analog hardware or digital software, offer a popular solution to this problem.

If noise is impacting controller performance, our first attempts should be to locate and correct the underlying fault. Filters are poor cures for a bad design or failing equipment.

If we decide to employ a filter in our loop, an algorithm designed to smooth the controller output signal holds some allure.

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