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Chapter 2 Function Reference — SCXI_Cal_Constants
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National Instruments Corporation 2-329 NI-DAQ FRM for PC Compatibles
calibrating, and then call SCXI_Cal_Constants again at the end of your calibration
sequence with
opCode = 4 to copy the user EEPROM area to the default load area. That
way there will be two copies of your new constants and you can revert to the factory
constants using
opCode = 4 without wiping out your new constants entirely.
Repeat the procedure above for each channel and range you want to calibrate. Subsequent
calls to
SCXI_AO_Write will use your new constants to scale voltage or current to the correct
binary value.
EEPROM Organization
The SCXI-1122, SCXI-1124, SCXI-1126, and SCXI-1141 modules have an onboard
EEPROM to handle storage of calibration constants. The EEPROM is divided into the
following three areas:
•The factory area is shipped with a set of factory calibration constants; you cannot write
into the factory area, but you can read from it.
•The default load area is where NI-DAQ automatically looks to load calibration
constants the first time you access the module during an NI-DAQ session using an
NI-DAQ function call, such as
SCXI_Reset, SCXI_Single_Chan_Setup, or
SCXI_AO_Write. When the module is shipped, the default load area contains a copy
of the factory calibration constants. When you write to the default load area using
SCXI_Cal_Constants, NI-DAQ also updates the constants in NI-DAQ memory.
•The user area is an area for you to store your own calibration constants that you calculate
by following the instructions above and using the
SCXI_Cal_Constants function. You
can also put a copy of your own constants in the default load area if you want NI-DAQ
to automatically load your constants for subsequent NI-DAQ sessions.