Introduction; Single Pid Controller; Reverse Acting (Base) - ABB AnalyzeIT AX460 User Manual

1 INTRODUCTION

The AX460 Single Input pH Analyzer has been enhanced with the addition of Proportional Integral Derivative (PID) control.
PID control can be either relay output (Time Proportioning or Pulse Frequency) or analog output.
The control output can be configured as either a (Reverse or Direct Acting) or as a (Bi-directional

Single PID Controller

Dual PI Controller
Acid/Base).
The output from the is assignable to either a relay or an analog output.
Single PID Controller
The outputs from the are assignable to either relays, analog outputs or one of each type.
Dual PI Controller
This supplementary manual provides additional information relevant to the PID control features of the analyzer and must be read in
conjunction with the User Guide (IM/AX4PH).
1.1 Single PID Controller – Fig. 1.1
The single PID controller is a basic feedback control system using three-term PID control with a local set point.
Manual Output
Control Set Point
Output 1
PID Control Loop
PID Output
Process Variable
Fig. 1.1 Single PID Controller
1.1.1 Reverse Acting (Base) Single PID Control – Fig. 1.2
Reverse acting control is used when the process pH is less than the required output pH. Normally, a base is added to the sample to
increase the pH value.
100%
Control
Output
Reverse
Acting
0%
0pH 7pH 14pH
Process Variable
Fig. 1.2 Reverse Acting (Base) Single PID Control
2