Rockwell-automation DeviceLogix System User Manual Bedienungsanleitung PDF herunterladen (Seite 29)

Publication RA-UM003B-EN-P - February 2010 29

Navigate the Function Block Editor Interface Chapter 2

Manual and Automatic Modes

The PID function block automatically provides bumpless

transfer from manual mode to auto mode. The PID function

block back-calculates the value of the integral accumulation

term required to make the CV output track the set output value

in manual mode. In this manner, when the loop switches to auto

mode, the CV output starts off from the set output value and no

"bump" in output value occurs.

Configuration Parameters

Configuration parameters allow you to set control loop features.

Deadband

The adjustable deadband is used to select an error range above

and below the setpoint where output does not change as long as

the error remains within this range. This deadband controls how

closely the process variable matches the set point without

changing the output.

Parameter Type Range Default Description

Control Action BOOL 0 Indicates the direction of control:

• 0 is E=SP-PV

• 1 is E=PV-SP

This parameter cannot be configured when the

DeviceLogix logic is in the Run mode.

Loop Update Time UDINT 0 Periodical time interval in microseconds for

output update.

This parameter cannot be configured when the

DeviceLogix logic is in the Run mode.

CV High Limit % REAL 0.0 ~ 100.0 0.0 System's maximum allowable value for the

Control Variable. The PID function block does

not output a CV that exceeds the High Limit.

CV Low Limit % REAL 0.0 ~ 100.0 0.0 Sytem's minimum allowable value for the

Control Variable. The PID function block does

not output a CV less than the Low Limit.

Deadband Value REAL 0.0 Error range above and below the setpoint. Enter

"0" to inhibit the deadband. The deadband has

the same scaled units as the setpoint.

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Rockwell-automation DeviceLogix System User Manual Bedienungsanleitung Seite 29