JYTEK NuDAQ PCI-69222, User Manual

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Calibration 65
5 Calibration
This chapter introduces the card calibration process to minimize
AD measurement errors and DA output errors.
5.1 Loading Calibration Constants
The PCI-69222/PCI-69223 is factory-calibrated before shipment.
The associated calibration constants of the TrimDACs firmware
are written to the onboard EEPROM. TrimDACs firmware is the
algorithm in the FPGA. Loading calibration constants is the pro -
cess of loading the values of TrimDACs firmware stored in the
onboard EEPROM. ADKLINK provides a software utility that auto -
matically reads the calibration constants, if necessary.
There is a dedicated space for storing calibration constants in the
EEPROM. In addition to the default bank of factory calibration con -
stants, there is one user-utilization bank. This bank allows you to
load the TrimDACs firmware values either from the original factory
calibration or from a subsequently-performed calibration.
Because of the fact that measurements and outputs errors may
vary depending on time and temperature, it is recommended that
you calibrate the card when it is integrated in your computing envi -
ronment. The auto-calibration function is presented in the follow -
ing sections.
5.2 Auto-calibration
Through the PCI-69222/PCI-69223 auto-calibration feature, the
calibration software measures and corrects almost all calibration
errors without any external signal connections, reference voltage,
or measurement devices.
The PCI-69222/PCI-69223 comes with an onboard calibration ref
-
erence to ensure the accuracy of auto-calibration. The reference
voltage is measured in the production line through a digital potenti -
ometer and compensated in the software. The calibration constant
is memorized after this measurement. We do not recommended
adjustment of the onboard calibration reference except when an
ultra-precision calibrator is available.