Wilco B.

@ptrumel Thnx for answering this question so quickly, but for clarity: Are you implying that we should combine the two different 0Vdc supplies on the RTN+iRTN side?

Hi, We have a discussion in our office concerning the correct way of wiring an external current signal 4-20mA to a 1756-IF16 module. (We do many different PLC brands and configurations, so my/our experience with Alan Bradley is of several years ago) We have several external current signals connected to these units. (And these systems are all situated on a ship.) Some are galvanic separated and others are not and have their 'own' power supply only a few are sensors that are loop powered by the Main PLC cabinet.   The issue: According to one colleague it is required to connect the RTN jumper wires to the negative of the main PLC cabinet to solve signal issues due to floating voltage. Although it will work, I am not sure if this is really necessary, and I don't like connecting the negative to other cabinets which have their own power supply... Alan Bradley does not indicate that this is required, only jumper wires to convert the circuit from voltage measurement to current. It is also disappointing that none of the (non-differential) examples of Alan Bradley show how to connect an external current signal (which would indicate if the extra negative to be needed)   Adding galvanic separators and connecting the RTN to the negative is in my opinion not so much a solution but an evasion of the question/issue.   Any knowledge out there? Thnx