sample rate / resolution relationship for USB-6351

[Reedayoungblood]

Do the AI resolution or AI accuracy on the USB-6351 vary at all with the sample rate?  For example, the datasheet for the 4070 DMM contains this chart of the sample rate/resolution relationship:

However, I don't see anything like this in the datasheet for the USB-6351.  I see where the absolute accuracy depends on the voltage range, but nothing tied to sample rate.  Does that mean I will get the same resolution (16-bit) and accuracy regardless of whether I am measuring a single channel at 10kS/s or 2 channels at 500kS/s each (1MS/s aggregate)?  Thanks.

[Jeff-P]

Hi Reedayoungblood,

From the datasheet, the USB-6351 can sample one channel at a max rate of 1.25MS/s with 16 bit resolution. So as long as your aggregate does not exceed 1.25MS/s you will not get losses in accuracy or resolution. I hope that helps.

[John_P1]

The FlexDMM has a sort of on-board averaging, so sampling for a longer duration will give a higher resolution.

The 6351 on the other hand uses a SAR ADC which is fixed at 16 bits of resolution.  However... your question about accuracy isn't as straightforward.  Changing the sample rate if you are acquiring from a single channel shouldn't affect accuracy.  When acquiring on multiple channels however, settling error can become a factor (there is a chart on page 2 of the specifications).  You need to allow enough time for the voltage on the ADC to settle to within the desired accuracy if you are acquiring on multiple channels.

Best Regards,