When the PID Adaptive Tuning attribute is set to True (Figure 1), the PID uses PRAC+ Adaptive Tuning to update the Eff Integral Time and Eff Proportional Band parameters based on system response.
Figure 1. Adaptive Tuning Attribute
The relationship between the PID Pre-Processor and the PID depends on how the two parameters are set and on the connections between the two logic blocks. In the example shown in Figure 2, the following occurs:
- The PID Pre-Processor uses the value of the Process ID activity input, which may not be the same as the default value of the Process ID in the PID Pre-Processor. If there is no connection for the input Process ID, it uses the default value in the PID Pre-Processor.
- The PID uses the values from the PID Pre-Processor where connections exist. In the example, the PID receives the values for Minimum Tune Band, Saturation Time, Interval, Proportional Band, Integral Time, Time Constant, Process Range, and Process Dead Time, rather than the default values of the PID.
Figure 2. PID and PID Pre-Processor Relationship