NI Digital Multimeter Device Gives Out of Range and NaN While Measuring Current/Voltage

Issue Details

I am using a PXIe-4081 to measure a DC current that ranges from 4-20 mA. However, when I try to measure this current using a 100 mA measurement range, the output shows "Out-of-Range" and "NaN". On the other hand, when I set the range to 1 A, the current is detected correctly.

Solution

It is a possibility that the digital multimeter (DMM) is receiving some common mode noise/spikes in your measured signal. Therefore, it is detecting a higher value on the inputs than your set measurement range. To ensure accurate measurements with your DMM, it's important to check its common mode rejection ratio (CMRR) on its respective specifications page. If the noise exceeds these specifications, the DMM's measurements may be impacted.

Check your signal carefully as such noise can be of a very high frequency and hence not easily detectable. If such a common mode noise is present, you might need to use an external "common mode choke" to suppress/eliminate this noise from your signal. For example, see such an arrangement below.



This way, the noise will be removed and you will be able to measure the signal correctly. If you are still experiencing the issue, contact NI Support.