Multifunction DAQ
Questions for AI GND in NRSE mode with a floating system
Dear members,
Regard to the document above, the simple system setup is RSE for floating systems, and NRSE for grounded systems.
But the problem is my measurement target system (Source) is sometimes grounded and sometimes not.
I'm using NRSE mode, because I saw that RSE mode makes small error values because of ground loop when Source is grounded.
What I worry about is that my DAQ AI SENSE and AI GND both are connected to only the ground signal of Source without bias resistors.
I connected AI GND to the ground signal of Source, because when Source is not grounded, the measured values are error values maybe because of common mode input range.
(My system is like this when Source is floating or grounded, both)
The measured values when Source is grounded or not, the both are very similar with the measured values of the next picture setup when Source is grounded (recommended).
But the document says AI GND should be connected to the positive signal and ground signal of Source both with bias resistors when Source is floating.
Question 1.
In my setup (AI SENSE and AI GND both are connected to the ground signal of Source without bias resistors), does it make something wrong critically?
Question 2.
If I must install bias resistor, can I connect AI GND to only the ground signal of Source, and skip connecting it to a positive signal?
Question 3.
Source has one ground signal and many positive signal pins, and I want to measure voltages of those many positive pins.
If I must install connect AI GND to the ground signal and positive signal of Source with bias resistors, what positive signal should I connect AI GND to?
Question 4.
When I connected AI GND to the ground and positive signals of Source with bias resistors, does it work with Source floating or grounded both?
Question 5.
Bias resistors should be same?
Thank you
Minjae Kim
