Despatch P1400+ Temperature Controller - Manual (Page 88)

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PI Control Type: Controller Definition
Proportional and Integral (PI) Control is used to control Modulating Valves. It is similar to PID
Control, but without Derivative (Rate) action that causes excessive valve movement.
Also refer to
Modulating Valve , PID Control , Rate , Tuning and Valve Motor Drive Control .
PID Control Type: Controller Definition
Proportional Integral and Derivative control maintains accurate and stable levels in a process (e.g.
temperature control). It avoids the oscillation characteristic of On-Off control by continuously
adjusting the output to keep the process variable stable at the desired setpoint.
Also refer to
Control Action , Control Type , Automatic Reset , Controller , Manual Mode , On-Off
Control , PI Control , Primary Proportional Band , Process Variable , Rate , Secondary Proportional
Band , Setpoint , Tuning and Valve Motor Drive Control .
PLC Type: General Definition
This stands for Programmable Logic Controller. A microprocessor based device used in machine
control. It is particularly suited to sequential control applications, and uses “Ladder Logic”
programming techniques. Some PLC’s are capable of basic PID control, but tend to be expensive
and often give inferior levels of control.
Also refer to
PID .