Controlling a Ratio (PID)

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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