Pro-EC44 2-Loop Graphical Profile Controller & Recorder
Pro-EC44 Product Manual - 59540-2 September 2014
Page 107
Integral Time Constant
To find the optimum integral time, decrease its value until the process becomes unstable,
then increase it a little at a time, until stability has is restored. Induce a load disturbance or
make a setpoint change to verify that the process stabilises. If not increase the value some
more and re-test. If the response is too slow, decrease the integral time, but avoid instability.
Integral Time
Too Short:
Overshoots and oscillates
Too Long:
Slow warm up and response
Derivative Time Constant
Initially set the derivative to between 1/4
th
and 1/10
th
of the Integral time value.
Increase the derivative time if the process overshoots/undershoots. Increase it a little at a
time, but if the process becomes unstable, decrease it until the oscillation stops. Induce a
load disturbance or make a setpoint change to verify that the process stabilises. If not
decrease the value some more and re-test.
Derivative Time
Too Long:
Oscillates and over corrects
when process disturbed
Too Short:
Slow warm up and disturbance
response under-corrects
Note:
When controlling a modulating valve, it is usually recommended that
derivative is set to OFF to avoid excessive valve activity. Derivative can cause
process instability in these processes.
Process Disturbance
Process Disturbance
Summary of Contents for Pro-EC44
Page 1: ...Pro EC44 2 Loop Graphical Profile Controller Recorder Pro EC44 User Guide 59540 2 ...
Page 2: ......
Page 6: ......