11-05-2013 10:46 PM
Hello,
I have an SCXI-1104C for monitoring single-ended DC voltages. I know that the SCXI module has differential inputs only, so I presumed that I would need to connect each individual negative terminal to ground.
However, I noticed that if I connect Signal- to the SCXI_ChassisGND, and Signal+ to SCXI_Ch0+, I still get the correct reading. The reading floats when I disconnect Signal- from SCXI_ChassisGND.
What am I observing here? Can I reliably use the SCXI-1104C for RSE measurements, by connecting Signal- to ChassisGND?
Thanks!
Solved! Go to Solution.
11-06-2013 01:27 PM
Hello JKSH,
Consider the connection for the SCXI-1104 where...
Ch0+ is connected to Signal +
Ch0- is connected to Nothing
This is an unguaranteed configuration where Ch0- is just floating at whatever voltage it was at last. This is probably somewhere around chassis ground because it was last connected to chassis ground. However, if you touched the Ch0- with a random voltage, your measurement would be disrupted and at an incorrect level.
When Ch0- is instead connected to some reference voltage, we guarantee the level and can acquire valid voltages.
I hope this helps!
-Eric E.
11-06-2013 09:17 PM