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Current loop wiring of pressure transmitter, controller and valve

Current loop wiring of pressure transmitter, controller and valve

Current loop wiring of pressure transmitter, controller and valve

(OP)
Newbie to the 4-20mA current loops so I'm wondering if anyone can help me with understanding how to connect the following devices. The individual product info has confused me so I'm hoping you experts can give me a clue:

1.) Rosemount 3051 pressure transmitter
2.) Honeywell UDC2500 controller
3.) Fisher valve w/ DVC600 controller.

intent is to take signal from transmitter, scale it in the controller, and send signal to the valve controller.

Do I use my existing 24vDC power supply to power the 3051 transmitter and send it's 4-20mA output to the UDC2500, then use the UDC2500 to power the current loop between it and the valve, or should all this be on one loop? Any help would be greatly appreciated, simple schematic would be great. Thanks in advance

RE: Current loop wiring of pressure transmitter, controller and valve

I have attached a drawing.
One wire is left off, it needs to be connected to a positive supply, I think one of the controller pins will provide that. Test with your meter in respect of terminal 27.
If you can't find a positive supply it's also possible to use an external power supply, negative connected to terminal 27, positive to transmitter positive.

http://honeywell.silverw.com/docs/51-52-25-127.pdf

Regards
Roy

RE: Current loop wiring of pressure transmitter, controller and valve

The loop power in a UDC is derived from either an auxiliary (retransmitting 4-20ma) output option or a solid state control output option, which is not likely to have on a current control output model.

It's just my opinion, but I never use the internal loop power on a UDC, I always install a 'real' external 24Vdc power supply.

An external power supply doesn't cost anymore than the aux out option, its presence is predictable and understandable to anyone familiar with loop powering, and it can be 'easily' changed out with any model/brand power supply, if needed, if it ever fails.   The UDC's internal supply fails on all these accounts.

Dan

 

RE: Current loop wiring of pressure transmitter, controller and valve

DanW has some good advice, the external power supply option is likely more robust, however the Fisher DVC however certainly uses the UDC's power.
On my project all the transmitters were 4 wire so I didn't need to add any but I remembered something in the manual about using the internal.
By the way, did you purchase a controller with the Auto/Manual option? They all have the buttons but some models have them dissabled in software. (you need a code to enable them)
If you respond give us the exact model No
Roy

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