National Instruments VXI-MIO Series - Manual (Page 94)

Chapter 5 Calibration
 National Instruments Corporation 5-3 VXI-MIO Series User Manual
module by calling the NI-DAQ or VXI plug&play instrument driver
calibration function.
To externally calibrate your module, be sure to use a very accurate
external reference. The reference should be several times more accurate
than the module itself. For example, to calibrate a 12-bit module, the
external reference should be at least
±
0.005% (
±
50 ppm) accurate. To
calibrate a 16-bit module, the external reference should be at least
±
0.001% (
±
10 ppm) accurate.
Other Considerations
The CalDACs adjust the gain error of each analog output channel by
adjusting the value of the reference voltage supplied to that channel.
This calibration mechanism is designed to work only with the internal
10 V reference. Thus, in general, it is not possible to calibrate the
analog output gain error when using an external reference. In this case,
it is advisable to account for the nominal gain error of the analog output
channel either in software or with external hardware. See Appendix A,
Specifications , for analog output gain error information.