ELVIS II units - when the DMM leads are connected together with the unit set to read AC current, the unit displays 3.56 mA? Is this normal?

[Diff]

For the ELVIS II unit with the instrument launcher selected - using the DMM to measure AC current: when the leads are connected together, the display show 3.56 mA. Is this normal? Readings do not become accurate until above 10 mArms.

[Deagle]

The AC Range of the DMM onboard the Elvis II is from 500 mA to 2 A RMS. Some inaccuracies outside the specified range are to be expected. Below is a link to the NI Elvis specifications sheet.

NI ELVIS II Series Specifications

http://www.ni.com/pdf/manuals/372590b.pdf

[charlesy]

Hello,

Yes, this is normal. The AC modes in DMMs become nonlinear with very small input signals near the bottom end of their ranges. The result is a residual error reading. This is not an offset -- as you noted, the accuracy improves as you increase the input signal. While this threshold is not specified for ELVIS II, it should be around 2% of range (10 mArms in the 500 mArms range, as you observed). By comparison, that threshold is specified as 5% of range for myDAQ and 1% of range for the PXI-4072. 

I hope this helps.

Charles Y.

National Instruments