Chapter5 Calibration
NI6013/6014 User Man ual 5-2 ni.com
accountthe fact that the device measurement and output voltage errors can
varywith time and temperature. It is better to self-calibrate when the device
is installed in theenvironment in which it is used.
Self-Calibration
The NI 6013/6014 can measure and correct for almost all of its
calibration-relatederrors without any external signal connections. NI-DAQ
provides a self-calibration method. This self-calibration process, which
generally takes less than two minutes, is the preferred method of assuring
accuracyin your applicatio n. Initiate self-calibration to minimize the
effectso f any offset and gain drifts, particularly those due to warmup.
Immediatelyafter self-calibration, the only significant residual calibration
error could be gain error due to time or temperature drift of the onboard
voltagereference. This error is addressed by external calibration, which is
discussedin the following section. If you are interested primarily in relative
measurements, you can ignore a small amount of gain error,and
self-calibration should be sufficient.
External Calibration
The NI 6013/6014 has an onboard calibration reference to ensure the
accuracyof self-calibration. Its s pecificationsare listed in Appendix A,
Specifications.The reference voltage is measured at the factory and stored
in the EEPROM for subsequent self-calibrations. This voltage is stable
enoughfor most applications, but if you are using t hed evice at an extreme
temperatureor if the onboard reference has not been measured for a year or
more, you may wish to externally calibrate the device.
An externalcal ibration refers to calibrating the device with a known
externalreference rather than relying on the onboard reference.
Redeterminingthe value of the onboard reference is part of this process and
theresults can be saved in the EEPROM, so you should not have to perform
an externalcalibration very often. You can externally calibrate the device
bycalling the N I-DAQcalibration function.
Toexternally calibrate the device, be sure to use a very accurate external
reference. The reference should be severaltimes more accurate than the
deviceitself.