Hello All,
I have a PID loop on a PLC 5/80E PLC that I have been using to control room temperature. Just recently, they've installed a 2nd temperature transmitter at the opposing end of the room.
So what I want to do is average the (2) temperature values as my PV for the loop. The problem is that the (2) transmitters have different ranges (ie; -18 to 38 C and -29 to 60 C). I'm thinking about averaging the (2) and/or automatically switching to one tx if the other fails. But I think to do this, I have to change the Engineering Units Min/Max of the PID loop every time that I switch transmitters.
Example:
Tx1 , PID Range = -18 to 38 C
Tx2, PID Range = -29 to 60 c
Averaging, PID Range = 0 to 100 C
Is there a better way of doing this?
I have a PID loop on a PLC 5/80E PLC that I have been using to control room temperature. Just recently, they've installed a 2nd temperature transmitter at the opposing end of the room.
So what I want to do is average the (2) temperature values as my PV for the loop. The problem is that the (2) transmitters have different ranges (ie; -18 to 38 C and -29 to 60 C). I'm thinking about averaging the (2) and/or automatically switching to one tx if the other fails. But I think to do this, I have to change the Engineering Units Min/Max of the PID loop every time that I switch transmitters.
Example:
Tx1 , PID Range = -18 to 38 C
Tx2, PID Range = -29 to 60 c
Averaging, PID Range = 0 to 100 C
Is there a better way of doing this?