Rockwell-automation DeviceLogix System User Manual Bedienungsanleitung PDF herunterladen (Seite 30)

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

Chapter 2 Navigate the Function Block Editor Interface

Zero-crossing is deadband control that lets the function block

use the error for computational purposes as the process variable

crosses into the deadband until the process variable crosses the

setpoint. Once the process variable crosses the setpoint (error

crosses zero and changes sign), and as long as the process

variable remains in the deadband, the function block considers

the error value to be zero. The deadband has the same scaled

units as the setpoint.

Output Limit

An output limit (percent of output) can be set on the control

output. When the function block detects that the output has

reached a limit, the PID function block automatically avoids

reset windup by preventing the integral term from accumulating

whenever the CV output reaches its maximum or minimum

values. The accumulated integral term remains frozen until the

CV output drops below its maximum limit or rises above its

minimum limit. Normal integral accumulation automatically

resumes.

Scaling Parameters

Scaling parameters allow you to set the output scale.

Parameter Type Default Description

PV Max REAL 0.0 Maximum value for the unscaled Process

Variable (PV).