I have a question regarding the Engineering Unit Min / Max and the Input Range Min / Max parameters on a PID block in a PLC5.
Typically I've seen these field's left at 0 to 4095 for Min / Max regardless of what we are running.
99% of the time the PV we are passing in to the loop is pre-scaled.
Lets say we have a flow control loop, with an analog in for flow that is pre-scaled to 0 to 300 LPM prior to being passed to the PID loop.
The CV output in 0-100% is written to a VFD that controls modulates accordingly.
If I change the Input Range and Engineering Unit Min/Max values to 0 and 300, will I see any change in loop behavior?
Right now those values are 0 to 4095. So I'm worried that the Error that is calculated with a Setpoint of say 81 is used differently in the PID algorithm when you input and EGU ranges are different (ie: an error of 10 on a range of 0 to 4095 and much "less" than an error of 10 on a range on 0 to 300).
Thanks.
Typically I've seen these field's left at 0 to 4095 for Min / Max regardless of what we are running.
99% of the time the PV we are passing in to the loop is pre-scaled.
Lets say we have a flow control loop, with an analog in for flow that is pre-scaled to 0 to 300 LPM prior to being passed to the PID loop.
The CV output in 0-100% is written to a VFD that controls modulates accordingly.
If I change the Input Range and Engineering Unit Min/Max values to 0 and 300, will I see any change in loop behavior?
Right now those values are 0 to 4095. So I'm worried that the Error that is calculated with a Setpoint of say 81 is used differently in the PID algorithm when you input and EGU ranges are different (ie: an error of 10 on a range of 0 to 4095 and much "less" than an error of 10 on a range on 0 to 300).
Thanks.
