how are these parameters in the Allen-Bradley PID instruction should be configured and where do these values come from



Process variable (pv)

Unscaled max and min



Control variables (cv)

Min and max



Engineering units

Min and max



Tie back

Min and max

 

In simple terms, most of these come from how your real-world signals are wired and scaled. The process variable (PV) unscaled min/max match the raw input range from your analog card (for example 0–32767 or 4–20 mA counts). The engineering units min/max are whatever that signal represents in real life (like 0–100 °C or 0–300 psi).
The control variable (CV) min/max define the output limits you allow the PID to send to the actuator (valve, VFD, etc.). Tieback min/max usually match the CV range and are used when you’re in cascade or tracking mode so the PID doesn’t jump when switching modes.