ADLINK USB-2405 - Manual (Page 51)

Calibration 41
USB-2405
4 Calibration
This chapter introduces the process of calibrating the USB-2405 to
optimize AD measurement.
4.1 Loading Calibration Constants
The USB-2405 is factory-calibrated before shipment, with associ-
ated calibration constants of the TrimDACs firmware written to the
onboard EEPROM. TrimDACs firmware is the algorithm in the
FPGA. Loading calibration constants entails loading the values of
TrimDACs firmware stored in the onboard EEPROM.
ADKLINK provides a software utility that automatically reads the
calibration constants, if necessary.
Dedicated space for storing calibration constants is provided in the
EEPROM. In addition to the default bank of factory calibration con-
stants, there is one user-utilization bank, allowing loading of the
TrimDACs firmware values either from the original factory calibra-
tion or a subsequently-performed calibration.
Since measurement errors may vary depending on time and tem-
perature, it is recommended that the USB-2405 module be cali-
brated in the existing testing environment, as follows.
4.2 Auto-Calibration
The USB-2405 auto-calibration utility measures and corrects
almost all calibration errors with no requirement for external signal
connection, reference voltage, or measurement devices. An
onboard calibration reference is provided to ensure accuracy of
auto-calibration. The reference voltage is measured in the produc-
tion line by a digital potentiometer and compensated in the soft-
ware. The calibration constant is stored after auto-calibration.
NOTE: NOTE:
The USB-2405 module should be warmed up for at least 15
minutes before initiating auto-calibration.