beautypg.com

Despatch P1400+ Temperature Controller User Manual

Page 88

background image

82

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

.