Micromod Micro-DCI: 53MC5000 Multi-Loop Process Controller FLEXIBLE CONTROL STRATEGIES - Manual (Page 108)

A.1.3 CS3 - RATIO CONTROLLER
The ratio PID controller is used where a controlled variable must automatically be maintained in
definite proportion to an uncontrolled or wild variable.
Loading CS3 initializes the ANI1 engineering span to 100.0, CON0 display mode to 3, CON0 set-
point mode to 1, and C081 to 1.0. The control scheme is shown in block diagram form in Figure A-
3. Also provided is Table A-3, which is a worksheet that shows the CS3 wirelist connections;
wirelist datapoints not connected are left at default. Table A-3 is partitioned by FCS module type
applicable to CS3 (those modules illustrated in Figure 2-1). The datapoint parameters for each
module are shown with their default values.
The following I/O assignments result from loading CS3:
ANI0 Controlled Variable
ANI1 Wild Variable
ANI2 Additive Feed Forward Input
ANI3 Tracking Input
ANO0 Control Output
CCI0 Force Output Tracking
CCI1 Ratio Enable
CCO0 Process Alarm 1
CCO1 Process Alarm 2
The PCS operates as a standard PID controller whether in ratio or local control. The essential as-
pect of the ratio controller is how setpoint push button actions are interpreted. While in ratio con-
trol, the push buttons modify the desired ratio (controlled/wild) value, indirectly affecting the
setpoint value. When in local control, the push buttons modify the setpoint value directly.
FCS 53MC5000 Flexible Control Strategy
A-18
413-TXT