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National Instruments Corporation
5-1
5
Calibration
This chapter discusses the calibration procedures for the NI 6013/6014.
NI-DAQ includes calibration functions for performing all of the steps in
the calibration process.
Calibration refers to the process of minimizing measurement and output
voltage errors by making small circuit adjustments. On the NI 6013/6014,
these adjustments take the form of writing values to onboard calibration
DACs (CalDACs).
Some form of device calibration is required for most applications. If you do
not calibrate the NI 6013/6014, the signals and measurements could have
very large offset, gain, and linearity errors.
Three levels of calibration are available to you and described in this chapter.
The first level is the fastest, easiest, and least accurate, whereas the last
level is the slowest, most difficult, and most accurate.
Loading Calibration Constants
The NI 6013/6014 is factory calibrated before shipment at approximately
25 °C to the levels indicated in Appendix A,
. The associated
calibration constants—the values that were written to the CalDACs to
achieve calibration in the factory—are stored in the onboard nonvolatile
memory (EEPROM). Because the CalDACs have no memory capability,
they do not retain calibration information when the device is unpowered.
Loading calibration constants refers to the process of loading the CalDACs
with the values stored in the EEPROM. NI-DAQ determines when loading
calibration constants is necessary and does it automatically. If you are not
using NI-DAQ, you must load these values yourself.
In the EEPROM, there is a user-modifiable calibration area in addition
to the permanent factory calibration area. The user-modifiable calibration
area allows you to load the CalDACs with values either from the original
factory calibration or from a calibration that you subsequently performed.
This method of calibration is not very accurate because it does not take into
