A
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5
UM344-2 APPENDIX A - FUNCTION BLOCK DESCRIPTIONS
September 1995
PD Controller
Controller .................................................................... On/Off
Controller Type....................................................... PID/PD/ID
Action...............................................................Reverse/Direct
Proportional Gain (PID & PD)...............................0.01 to 100.0
Time-Integral.........................................0.01 to 1000 min/repeat
Time-Derivative.............................................. 0.01 to 100.0 min
Derivative Gain......................................................1.00 to 30.00
Manual Reset (PD only).......................................0.0 to 100.0%
Manual Reset Tracking (PD only)..................................No/Yes
The PD controller is a proportional only controller with manual reset which can be selected as tracking or
non-tracking.
The track function block will force the controller output to track the feedback, and if manual reset tracking
is selected, the manual reset (MR) will also track the feedback when the controller is in manual. In either
case, the controller will always go back to AUTO with the output equal to the feedback. The reset value
will then return to the value of MR with the time constant established by the integral time (TI). Since the
default value of TI is 100 min., it should be reduced (e.g. 0.01 min) when using this controller type. The
TI Time Constant is selected for the rate at which the controller should return to normal operation after
switching from manual to auto. Bear in mind that the TI time in the PD Controller is not an integral time
and does not affect control stability.
If the derivative time TD is set equal to 0.0, the derivative section is eliminated.
Block Diagram, PID Controller
PV
TDs
TD
DG s + 1 +
+
+
+
+ / -
+ / -
SP
PG GE
R
s + 1TI
1
Output
F
X02879S0
Output
SP
PV
PID
PD
ID
PD Controller