Controlling a Ratio (PID)
You can maintain two values in a ratio by using these parameters:
- Uncontrolled value
- Controlled value (the resultant setpoint to be used by the PID instruction)
- Ratio between these two values
Ladder Diagram
TIP:
Tip: To avoid locking up the PID with invalid internal floating point values, ensure the PV is not INF or NAN before invoking the instruction such as:
XIC (PC_timer.DN)
MOV(Local:0:1.Ch0Data, Local:0:1.Ch0Data)
XIO(S:V)
PID(...)
Structured Text
pid_2.sp := uncontrolled_flow * ratio
PID(pid_2,pv_2,tieback_2,cv_2,0,0,0);
TIP:
Tip: To avoid locking up the PID with invalid internal floating point values, ensure the PV is not INF or NAN before invoking the instruction such as:
XIC (PC_timer.DN)
MOV(Local:0:1.Ch0Data, Local:0:1.Ch0Data)
XIO(S:V)
PID(...)
For this multiplication | Enter this value |
|---|---|
Destination | Controlled value |
Source A | Uncontrolled value |
Source B | Ratio |
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