Single and Dual Input Analyzers for Low Level Conductivity
AX410, AX411, AX413, AX416, AX418, AX450, AX455 & AX456
Appendix B
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IM/AX4CO Issue 11
Appendix B
B.1 Single PID Controller
The single PID controller is a basic feedback control system using three-term PID control with a local set point.
B.1.1 Reverse Acting Single PID Control
Reverse acting control is used when the process conductivity is less than the required output conductivity.
Fig. B.1 Single PID Controller
Fig. B.2 Reverse Acting Single PID Control
Process Variable
Control Set Point
Manual Output
PID Output
Output 1
PID Control Loop
Control
Output
100%
0%
0%
50%
100%
Reverse
Acting
Process Variable Range
