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National Instruments Corporation
5-1
5
Calibration
This chapter discusses the calibration procedures for the NI 6115/6120.
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 6115/6120,
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 device, the signals and measurements could have very
large offset, gain, and linearity errors.
Three levels of calibration are available to you and are 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 Stored Calibration Constants
The NI 6115/6120
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 this is
necessary and does it automatically.
In the EEPROM, there is a user-modifiable calibration area in addition to
the permanent factory calibration area. Hence, you can load the CalDACs
with values either from the original factory calibration or from a calibration
that you subsequently performed.
