APPENDIX B

BASICS OF PID CONTROLLERS

Each of the three Proportional-integral-derivative (PID) controller modes have distinct advantages and disadvantages. Here is a review of the basic functionality of each mode.

Figure B.1 shows the contribution of each mode to the output for a setpoint change. In this example, the proportional mode and the derivative mode are acting on the error (the difference between the setpoint and the process variable [PV]) rather than just on the PV. In the time period shown, there is no update from the process measurement so we can see more clearly the function of each mode without any feedback from the process.

PROPORTIONAL MODE BASICS

The proportional mode provides an immediate reaction to a change in the PV. If the ...

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