How to connect to a output module that acts as a current sink with a common ground

[gti]

I have a Simpson Power Meter, GIMA, with a Output Options Module.  The Module provides for 4-20 ma signal transmission up to 4 variables.  It acts as a current sink with a common ground; please see the Module schematic in the attachment.  Attempts to wire the signals to FP-AI-110 module have failed.  Initially, the 24 Vdc power from NI was used and the input was configured as a 4-20 ma input...this did not work.  Second attempt signal isolators were installed and the meter power supply was used to connect the signal to self-powered signal isolators from Crompton (250-ISAU-HG).  The isolator output had a 250 ohm resistor across it and the AI-110 was configured for a voltage input...but this wiring failed as well.  Advice on how to make this connection work would be deep welcomed and appreciated.

[SimonH]

gti,

As both modules are current sinks with common grounds I don't think you'll be able to configure the AI module for taking a current measurement.

You might however be able to hook these up to take a voltage measurement.

This KB explains how you would set this up for digital inputs:
How Do I Connect Two Sinking I/O or Two Sourcing I/O Together?

I think that by selecting an appropriate pull-up resistor and voltage source you will be able to take a voltage reading that reflects the current going into the AO module.

I hope this helps.

Regards,

Simon H
Applications Engineer

[gti]

Simon, thanks for the reply.  The holidays have delayed further troubleshooting on our end.  We will review your advice and hopefully resolve the problem.  We have also sent a email to the electonic circuit designer who resides in England, the name is ND Meters, for assistance.  A little side note; one reason the Simpson meter was selected was that it was made in America, no offense to our global brothers.  We are definintely in a world economy.  Thanks again.