National Instruments AT E Series - Manual (Page 105)

Chapter 5 Calibrating the Device
© National Instruments Corporation 5-3 AT E Series User Manual
a 16-bit device, the external reference should be at least ±0.001%
(±10 ppm) accurate.
For a detailed calibration procedure for the AT E Series device, refer to
the E Series Calibration Procedure by clicking Manual Calibration
Procedures at
ni.com/calibration .
Other Considerations
The CalDACs adjust the gain error of each AO 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 AO gain error when using an
external reference. In this case, it is advisable to account for the nominal
gain error of the AO channel either in software or with external hardware.
Refer to Appendix A,
Specifications , for AO gain error information.