Measurement Computing PCM-DAS16D/12 - Manual (Page 13)

4.1.2 Differential Inputs
Differential inputs measure the voltage between two distinct input signals.
Within a certain range (referred to as the common mode range), the measure-
ment is almost independent of signal source to PCM-DAS16x/12 ground
variations. A differential input is also much more immune to EMI than a
single-ended one. Most EMI noise induced in one lead is also induced in the
other, the input only measures the difference between the two leads, and the
EMI common to both is ignored. This effect is a major reason there is twisted
pair wire as the twisting assures that both wires are subject to virtually identi-
cal external influence. The diagram below shows a typical differential input
configuration.
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