During self-calibration, DAQmx will read the onboard reference voltage and adjust calibration coefficients (stored in EEPROM) for any differences. These coefficients have a limited range, and cannot account for large differences between the onboard reference voltage and the nominal reference voltage.
If this is the cause, you can verify the onboard reference voltage in MAX. Figure 1 shows a MAX test panel that is set to read this voltage on an NI PCI-6036E multifunction DAQ device.
Figure 1. Reference signal is shown at nominal value. Note that Max Input Limit= 5.01V and Min Input Limit=4.99V
If the voltage read on this internal channel is visibly lower than the nominal reference, the card may be outside the range of self-calibration and may require external calibration or repair if the card is damaged. NI provides calibration services
and repair services
for devices that need external calibration or repair. For more information about external calibration, see the "Additional Information" section below.
If you are not able to see these internal channels for your device, see Internal Channels Missing from Cards in NI-DAQmx