Several single ended output and PSU powered transducers are tens of meters apart from each other outputting 0 to 10V DC like voltages.
Some are temperature transducers some are force transducers ect. Their outputs all go to a single DAQ board which essentially multiplexes these channels and logs the data.
The DAQ board is also single ended and non referenced earth grounded and named as NRSE in the below illustration. The transducer signals are conveyed through BNC coaxial cables. Tr represents transducers below:
I’m planning to star-ground all power supply negative terminals and sensor shields at a single point and earth ground them. So none of the sources will be floating wrt earth. Since the DAQ is NRSE its analog ground will be floating with respect to earth.
I only found this document related topic http://www.ni.com/white-paper/3344/en/.
And mine is the one below encircled in red:
In my case, as I have explained with my first illustration many inputs actually nine inputs from transducers apart from each other will be coupled to the DAQ in NRSE configuration.
Do I really need to star-ground the DC negative terminals and transducer shields at a single point? SG is the signal Ret is the return wires going to the AISENSE. (For a particular case I got a better result earthing the DC terminal instead of return wire; it was CM interference due to SMPS transformer), thats why I earth ground the transducer’s from their power supply negative terminal in my illustration.
Basically what Im asking is the star connected node(red question mark) need to be earth grounded as well?:
AI SENSE is like diff ended with common returns.
AI GND and AI SENSE should not be connected thats what I heard from manufacturer for AI SENSE used scheme. Figure 1 SE scheme must not be used it causes parasitically coupled ground loops.
Now the transducers are powered by power supplies and power supply ground and transducer ground is not isolated.
In Figure 2 if I use AI SENSE and if I also route PSU ground to AIGND or to the nearest earth I get very good results. So it seems to me if I use AI SENSE scheme and a third wire from the red point(the PSU ground) to the nearest earth(yellow) or to AIGND(green) things are fine.
But since I have many of these I was asking should I use the green or yellow route in Figure 2.? Also there are 10 inputs in that case where should these yellow or green wires be star grounded?
But I can assure you SE scheme and tying AI GND to AI SENSE cannot be done. So please the answer be none of that two. AI GND is always earthed through PC motherboard. AI SENSE should not be wired to AI GND. Pls provide a simple drawing in the answer makes things easier to follow.