No, most likely your device is not defective. The NI 9205 is an isolated module(Channel-to-Earth Ground Isolation). As a result, the analog front end of the device is floating relative to the cDAQ/cRIO chassis ground. Thus, per the getting started guide, you must always connect the COM pin of your NI 9205 to a ground reference.Please refer to the page 17 to 20 of NI 9205 Getting Started Guide for the connection diagram of Grounded Differential, Floating Differential, Referenced Single Ended (RSE) and Non-Referenced Single Ended (NRSE) voltage signals respectively.
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