Answer / mathan

proportional -it is the present error and it can be adjusted by gain.
integration - past error and can be adjusted by resetting functions
derivatives - future error and can be calculated by rate of change of time

Answer / carl_ellis

PID provides a modulated output response to an error signal,
where error is the difference between what you want, the
setpoint, and what you have, the process variable.

PID uses an output response proportional to the input span
(P = proportional), modified by the accumulated error over
time (I = integral) and modified by the rate-of-change of
the error (D=derivative).

Carl Ellis
Measure First

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