ADLINK PXI-2502 - Manual (Page 57)

Calibration
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5.1 Auto-calibration
The auto-calibration feature of DAQ/PXI-2500 SERIES facilitates users
completing a calibration process, without the necessities for any external
voltage references or measurement devices.
The on-board auto-calibration circuitry is composed of a precision
band-gap voltage reference, an ADC and a TrimDAC. TrimDAC is a
multi-channel DAC that generates DC offsets that counteract the offsets
from the main DACs. Digital codes for the TrimDAC, as well as the tem-
perature and the date of the calibration, are stored in the onboard
EEPROM. We do not recommend end-users to adjust the onboard
band-gap voltage reference in anyway, unless an ultra-precision calibrator
is available.
Due to temperature, humidity variations, and component aging, the preci-
sion of DAQ board may degrade over time. It is suggested that users pe-
riodically calibrate the DAQ board. The user calibration constants can also
be stored in the on-board EEPROM.
NOTE:
1. Before auto-calibration procedure starts, it is recommended to warn up
the board for at least 15 minutes.
2. Please remove the cable before auto-calibration, because the D/A
outputs would be changed in the process.
5.2 Saving Calibration Constants
An on-board EEPROM is used to store calibration constants. In addition to
a default bank that stores factory calibration constants, there are three user
banks. Users can save the subsequently performed calibration constants
in anyone of these user banks. ADLink provides software for users to save
calibration constants in an easy manner.
5.3 Loading Calibration Constants
Users can calibrate DAQ board in three sites and store the calibration
constants into different user banks. When moving DAQ board from one
site to another, users can load the calibration constants without
re-calibration. ADLINK provides software for users to load calibration
constants in an easy manner.