Determine expected output voltage range for PXI-6289.

[epsilon-delta]

For the PXI-6289, the AO range accuaracy is specified as 259 uV for the -1 to +1 volt range.  The AO is 16 bit.  The minimum resolution should be 2VDC/(2^16)=30.5 uV.  Given the stated accuracy and resolution, how would I calculate the expected range of output voltages?  As an example, lets say the commanded output voltage is 100 mV.  What range of voltages would the output voltage fall within?  Thank you.

[Margaret F.]

Hello,

Thank you for posting to the NI forums. It sounds like you are questioning what output range you can expect based on the specified accuracy of the PXI-6289. If the output voltage is 100mV, then you can expect 100mV +/- 259uV as your output reading. Please remember the caveats to accuracy listed in the AO Absolute Accuracy table of the 6289 Specifications.  

"Absolute Accuracy at full scale numbers is valid immediately following internal calibration and assume the device is operating within 10 °C of the last external calibration.

Accuracies listed are valid for up to two years from the device external calibration." (page 7 of PXI 6289 Specifications)

[ChrisR.]

Actually, the 259 uV is for a signal at full-scale.  At 100mV, which is 10% of full scale on the 1V range, the gain error terms would be reduced by a factor of 10.  By my calculations from the published accuracy table in the specifications, that brings the total to:

 (85ppm + 25ppm/°C x 1°C + 1ppm/°C x 10°C) x 100mV + (57ppm + 50ppm/°C x 1°C + 32ppm) x 1V = 151uV

I'm not sure why the AO accuracy table doesn't show how to do the calculations the way the AI accuracy tables do on the previous pages.

Chris