4-20active non isolated on 9208

[rozzilla]

i have an valuable (60000$) instrument which has 8ch (16 wires with + ,- label) 4-20mA analog out non isolated. i wish to log their result via a 9208 module on cDaq. The question is how to wire it on the 9208. I guess i should short all - wires on 9208 COM then plug +s on AiX. But this way i think i do a ground loop between instrument ground and module. On the same cDaq i have probes with a lot of different PSUs and  i cannot risk the safety of this instrument. Any suggestion is well accepted.

Regards

manfredi

[m.amoruso]

Hi,

I can confirm that the 9208 module provides isolation Channel-To-Ground but it is not isolated Channel-To-Channlel. What kind of measures do you do? It might be more useful to use an isolated module Channel-to-Channel like this:

https://www.ni.com/en-us/shop/model/ni-9219.html

Alternatively you need to isolate the channels externally. I attach the following documents that may be helpful:

https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/analog-fundamentals/grounding-c...

[rozzilla]

its a real time GC, the constructor says i can short their common but i still dont know if its shared between them or not. i guess isolation between ground its just what i need to have. thank you for the answer and article