A 2 wire Transmitter input to two PLC systems.

[umaruet]

Hi
we have a 2 wire level Tx. as a input to a DCS(ABB, AC110) system(24VDC,active analog input card). now we want the same level Tx. input at some other PLC system(SLC500).do we need an isolator? if yes,then of what type(loop powered or seperately powered)?

Regards.
uaruet

 

[JesperMP]

Use an isolator.
Power the isolation amplifier from the same source that powers the 4-20mA transmitter.

 

[RobD]

It is always advisable to use isolators when inputing one signal to two differnet systems. (ABB use that a lot on Advant systems) its to do with grounding issues. Whether loop powered or ext 24Vdc powered its all up to whats available and what kind of input the SLC ie source/sink. Some isolators (P+F or MTL) are quite good in that you can have which ever configuration you want - eg
1)active input/passive output (AC110 powers the input loop and SLC powers output loop)
2)active input/active output (AC110 powers input loop and SLC sinks output loop)

The choice is yours just ensure that your isolator takes in an active input ie it does not try to power the transmitter also.

Good luck

 

[BobB]

M-System make an isolated transmitter with 2 analogue outputs, one to each system.