SCXI-1112 Calibration Details

[MarkMoss]

I just received a few SCXI-1112 cards for which I also ordered the detailed calibration.  Some of the information on the detailed calibration report don't appear, at first glance, to match up with the specification on the SCXI-1112 manual.  I'm hoping somebody here can fill in the gaps for me.

First, is there a calibration procedure available for the SCXI-1112 which might answer my questions without a lot of digging?

Now to the details:

According to the detailed calibration report (NI had esz Elektronik-Service GmbH out of Germany perfom the calibration), the calibration lab applied a +90 mV input and a -90 mV input to each channel, and verified that the output from the SCXI-1112 was within ±48 μV of the applied signal.  I'm just not sure where this ±48 μV limit comes from.

The specifications section from the SCXI-1112 manual lists the following:

Nonlinearity: 0.005% of FSR = 10 μV assuming a 200 mV (±100 mV) full scale range.

Offset error after calibration: 20 μV.

Gain error after calibration: 0.005% of a 90 mV reading = 4.5 μV.

If I simply add up these numbers, the output from an SCXI-1112 which meets specifications should be 90 mV ±34.5 μV  (not ±48 μV) with a 90 mV signal applied.  What am I missing here?

Mark Moss

Electrical Validation Engineer

GHSP 

[Corby_B]

Hello MarkMoss,

Thanks for your post and questions about calibration.

You are right in your calculations for the accuracy of the SCXI-1112 and that it should be somewhere in the range of  ±35 μV given that the input is 90mV. The value on your callibarion report also takes into account the system noise of the SCXI-1112, which the manual states is 5 μV of the signal input. There is also an off set of the DMM used to callibrate the 1112 as well. Even though the equipment that is used to calibrate your SCXI-1112 is callibrated there is also some error associated with it. So this could make up the extra 8 μV after taking into account the system noise. Let me know if this address your concerns or questions about the callibration of your SCXI-1112. Have a great day Mark!
 

Cheers!

Corby_B