What is a PID/Process controller?
This type of feedback controller has a single-loop (one channel of control) and utilizes a PID (proportional-Integral-Derivative) control algorithm. The output (control variable or CV) of this controller is based on the error created by a user defined set point (SP) and a process measurement (process variable or PV). The PID algorithm defines how each element acts on the error signal created. Proportional • The proportional term simply responds proportionally to the current size of the error. • The loop controller calculates a proportional term value for the PID calculation. • When the error is zero, the proportional term is also zero. Integral • The integral (or reset) term integrates (sums) the error values. • Starting from the first PID calculation after entering auto-mode, the integrator keeps a running total of error values. • The running total represents the constant output required to hold the current PV. Derivative • The derivative (rate) term responds to change in the current
