When creating a HART network, assuming the instruments are run in parallel, will the instruments still give a 4-20 mA signal up to the backbone? I have a tank bay with 8 tanks. I need to get the level data to the control room, but I have no analog inputs left on the PLC, nor the room to add cards. I was thinking I could put all of the levels in parallel and use a HART to Modbus TCP gateway, but I need to retain the local panel displays for the tank levels. This is what I have in mind; would it work?
Yes, it will work if your system supports HART-enabled transmitters either inbuilt or with HART-multiplexers.
You have to use HART-data only for measuring the tank levels.
The 4-20 mA will be used for powering the transmitters and not for reading the measurements via 4 to 20 mA (In your case).