GE AF-600 FP Design Manual page 32

Example:
A two zone two setpoint application Zone 1 setpoint is 15 bar and the feedback is 5.5 bar. Zone 2 setpoint is 4.4 bar and the feedback is 4.6 bar. If Multi Setpoint
Max [14] is selected, Zone 1's setpoint and feedback are sent to the PID controller, since this has the smaller difference (feedback is higher than setpoint, resulting
in a negative difference). If Multi Setpoint Min [13] is selected, Zone 2's setpoint and feedback is sent to the PID controller, since this has the larger difference
(feedback is lower than setpoint, resulting in a positive difference).
2.8.6 Feedback Conversion
In some applications it may be useful to convert the feedback signal. One example of this is using a pressure signal to provide flow feedback. Since the square
root of pressure is proportional to flow, the square root of the pressure signal yields a value proportional to the flow. This is shown below.
AF-600 FP Design Guide
2
31