West Control Solutions ProVU 4 - Manual (Page 77)

ProVU4 Controller, Profiler & Recorder/Controller - Product Manual
Page 76 Manual Tuning 59407, Issue 1 – March 2008
Fine Tuning.
A separate cycle time adjustment parameter is provided for the Primary and Secondary
control when using time proportioning control outputs.
Note:
Adjusting the cycle time affects the controllers operation; a shorter cycle time gives control
that is more accurate, but mechanical components such as relays have a reduced life
span.
1. Increase the width of the proportional band if the process overshoots or oscillates
excessively.
2. Decrease the width of the proportional band if the process responds slowly or fails to
reach setpoint.
3. Increase the automatic reset until the process becomes unstable, then decrease until
stability has been restored.
Note:
Allow enough time for the controller and process to adjust.
4. Initially add rate at a value between 1/4
th
and 1/10
th
of the automatic reset value.
5. Decrease Rate if the process overshoots/undershoots or oscillates excessively.
Note:
When controlling a modulating valve, it is recommended that Derivative is set to OFF to
avoid excessive valve activity. Derivative can cause process instability in these processes.
6. After making all other adjustments, if an offset exists between the setpoint and the process
variable use the Bias (manual reset) to eliminate the error:
Below setpoint - use a larger value
Above setpoint - use a smaller value.