NI USB-6210 noise and bias problem

[Mehrdad_A]

I am working with NI USB-6210. I am going to use the maximum resolution which is 6.4 uV. But the problem is that even when the input is short circuit the reading is in range of 30 uV to 100uV. I did the reading with differential input, I connected the negative input first directly to Analog GND and then through a 82K resistor and the last time I used two 82K resistors for negative and positive inputs, but the problem still exists. I do the reading with MATLAB codes.

ps: always there is a 24.5 HZ component in spectrum of voltage

[Scott-M]

Hi Mehrdad,

The accuracy of the 6210 can be found on pg. 4 of the manual linked here.

The absolute accuracy listed for your device at the smallest range (200mV) is listed at 88 uV, so your reading of 30 uV sounds about right. The resolution you mentioned of 6.4 uV is the code width (range/2^(#ofbits)), however the full calculation is more complex, and can also be found on pg 4 of the manual.

Let us know if you have any further questions.

Thanks

Scott M.