WIKA T53 - Manual (Page 31)

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4.0 PID Control Block, Fieldbus Foundation
4 .1 .Introduction:
T53 .is .fitted .with .a .PID .Control .Block .which .can .only .be .used .in .Fieldbus .Foundation .installa-
tions . .The .PID .Block .is .constructed .according .to .standard .specifications .outlined .in .Fieldbus .
Foundation .and .producer .specific .parameters .have .not .been .added . .Please .notice .that .the .
PID .function .is .not .specified .in .the .Profibus .Nutzerorganisation .and .thus .cannot .be .used .in .
Profibus .installations .
4 . .Overview
The .PID .block .is .key .to .many .control .schemes .and .is .used .almost .universally, .with .the .ex-
ception .of .PD, .which .is .used .when .the .process .itself .does .the .integration . .As .long .as .an .error .
exists, .the .PID .function .will .integrate .the .error, .which .moves .the .output .in .a .direction .to .cor-
rect .the .error . .PID .blocks .may .be .cascaded .when .the .difference .in .process .time .constants .of .
a .primary .and .secondary .process .measurement .makes .it .necessary .or .desirable .
4 .3 .Schematic:
4 .4 .Description
The .Process .Value .to .be .controlled .is .connected .to .the .IN .input . .This .value .is .passed .through .
a .filter .whose .time .constant .is .PV_FTIME . .The .value .is .then .shown .as .the .PV, .which .is .used .
in .conjunction .with .the .SP .in .the .PID .algorithm . .A .PID .will .not .integrate .if .the .limit .status .of .IN .
is .constant . .A .full .PV .and .DV .alarm .sub-function .is .provided . .The .PV .has .a .status, .although .it .
is .a .Contained .parameter . .