National Instruments NI 785xR - Manual (Page 55)

Chapter 3 Calibration (NI 783xR/784xR/785xR Only)
© National Instruments Corporation 3-3 R Series Intelligent DAQ User Manual
To externally calibrate your device, use an external reference several times
more accurate than the device itself. For more information on externally
calibrating your NI 783xR/784xR/785xR device, refer to the NI 783xR
Calibration Procedure for NI-RIO, found on
ni.com/manuals .