User Manual
3200 Series
68 Part No HA028651 Issue 11.0 July-12
11.3.10
Manually Setting the Cutback Values
Enter the PID terms calculated from the table in section 11.3.8 before setting cutback values.
The above procedure sets up the parameters for optimum steady state control. If unacceptable levels of overshoot or
undershoot occur during start-up, or for large step changes in PV, then manually set the cutback parameters.
Proceed as follows:
Initially set the cutback values to one proportional bandwidth converted into display units. This can be calculated by
taking the value in percentage that has been installed into the parameter ‘PB’ and entering it into the following formula:-
PB/100 * Span of controller = Cutback High and Cutback Low
For example, if PB = 10% and the span of the controller is 0 -1200
O
C, then
Cutback High and Low = 10/100 * 1200 = 120
If overshoot is observed following the correct settings of the PID terms increase the value of ‘CBLO’ by the value of the
overshoot in display units. If undershoot is observed increase the value of the parameter ‘CBHI’ by the value of the
undershoot in display units.
Display Units
Setpoint
Initial overshoot
PV approaching SP from
below – adjust CBLO
Initial undershoot
PV approaching SP from above
– adjust CBHI
Time
Summary of Contents for XST-2-0-12-1V1-E28
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