ICP DAS USA I-8017 Series, User Manual

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I-8017/I-9017 Series I/O Module User Manual V3.0.3 P.90
5.3. What to do when the data read from the module seems unstable
If the voltage can be measured correctly when testing using a battery, but not when using the real
signal source, the error may be caused by any or all of the following factors:

A noise-corrupted signal source

Instability in the signal source

A floating signal source that is not referenced to a system ground(earth or building ground)
Because of the nature of the high-speed data acquisition function on the module, any noise
coupled to a signal, or any change in voltage on an unstable source, is also captured. In this
situation, signal filtering or isolation should be considered in order to enhance the quality of the
signal.
It is recommended that the V- pin is connected to the AGND (system ground) pin when measuring
differential signals, as shown in the figure below.