Measurement Computing PCM-DAS16x/16 - Manual (Page 21)

6.1.3 Differential Inputs
Differential inputs measure the voltage between two distinct input signals. Within a
certain range (referred to as the common mode range), the measurement is almost
independent of signal source to PCM-DAS16x/16 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 identical external influence. The diagram below shows a typical differential
input configuration.
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