Measurement Computing PC104-DAS16JR/12 - Manual (Page 13)

A floating differential hookup is handy when the signal source is floating with respect
to ground, such as a battery, 4-20 mA transmitter or and the lead lengths are long or
subject to EMI interference (Figure 2-5).
Figure 2-5. Floating Source Differential Input
The floating differential input will reject up to 10V of EMI energy on the signal wires.
WARNING
Check it with a ohmmeter to determine that the signal source really
floating before risking the board and the PC!
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