Calibration - National Instruments DAQCard-1200 User Manual

Calibration

© National Instruments Corporation
This chapter discusses the calibration procedures for the DAQCard-1200
analog I/O circuitry. However, the DAQCard-1200 is factory calibrated,
and National Instruments can recalibrate your card if necessary. To
maintain the 12-bit accuracy of the DAQCard-1200 analog input and
analog output circuitry, recalibrate at 6-month intervals.
There are two ways to perform calibrations.
• Use the NI-DAQ
method.
• Use your own register-level writes to the calibration DACs and the
EEPROM.
The DAQCard-1200 is software calibrated, so there are no calibration
trimpots. The calibration process involves reading offset and gain errors
from the analog input and analog output sections and writing values to the
appropriate calibration DACs to null the errors. There are four calibration
DACs associated with the analog input section and four calibration DACs
associated with the analog output section, two for each output channel.
After the calibration process is complete, each calibration DAC is at a
known value. Because these values are lost when the card is powered down,
they are stored in the onboard EEPROM for future reference.
The factory information occupies one half of the EEPROM and is
write-protected. The lower half of the EEPROM contains user areas for
calibration data. There are four different user areas. When the
DAQCard-1200 is powered on, or when the conditions under which it is
operating change, you must load the calibration DACs with the appropriate
calibration constants.
If you use the DAQCard-1200 with NI-DAQ and LabVIEW or
LabWindows/CVI, the factory calibration constants are automatically
loaded into the calibration DAC the first time a function pertaining to
the DAQCard-1200 is called, and then each time you change your
configuration. You can, instead, choose to load the calibration DACs with
calibration constants from the user areas in the EEPROM, or you can
recalibrate the DAQCard-1200 and load these constants directly into the
calibration DACs.
function. This is the simpler
Calibrate_1200
5-1
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DAQCard-1200 User Manual