West Control Solutions 8700+ - Manual (Page 125)

1 /
4
-DIN, 1 /
8
-DIN & 1 /
16
- DIN Controllers & Indicators - Product Manual
Page 120
Manual Tuning 59305, Issue 7 – March 2014
Manually Fine Tuning.
A separate cycle time adjustment parameter is provided for each time proportioning control
output.
Note:
Adjusting the cycle time affects the controllers operation; a shorter cycle time gives more
accurate control but electromechanical 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 Rate (Derivative) is set to 0
seconds (OFF) to avoid excessive valve activity.
Rate can cause process instability.
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 bias value
Above setpoint - use a smaller bias value.