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- DIN Controllers & Indicators - Product Manual
Page 90 Manual Tuning 59305, Issue 5 – March 2005
P
Input Span
T
6
11 Manual Tuning of Controllers
Controllers Fitted With Primary Output Only
Before starting to tune a controller, check that the Setpoint Upper Limit (:-=+) and Setpoint
Lower Limit (:-++) are set to safe levels.
The following simple technique may be used to determine values for the Primary Proportional
Band (-6B-), Integral Time Constant (59:#) and Derivative Time Constant (05#;).
CAUTION:
This technique is suitable only for processes that are not harmed by large
fluctuations in the process variable. It provides an acceptable basis from which to
start fine-tuning for a wide range of processes.
1. Set the setpoint to the normal operating process value (or to a lower value if overshoot
beyond this value is likely to cause damage).
2. Select On-Off control (i.e. set -6B- = 0).
3. Switch on the process. The process variable will oscillate about the setpoint. Note (a) the
Peak-to-Peak variation (P) of the first cycle i.e. the difference between the highest value of
the first overshoot and the lowest value of the first undershoot, and (b) the time period of
the oscillation (T) in minutes. See the example diagram below - Manual Tuning.
4. The PID control parameters should then be set as follows:
-6B- = x 100
59:# = T minutes
95K; = minutes
Note:
After setting up the parameters, return the controller to operator mode to prevent
unauthorised adjustment of the values.
Figure 39. Manual Tuning
Time
Process Variable
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