JYTEK PCIe-69834, Руководство пользователя

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Calibration 35
Appendix A Calibration
This chapter introduces the calibration process to minimize analog
input measurement errors.
A.1 Calibration Constant
The PCIe-
69834
is factory calibrated before shipment, with
associ-ated calibration constants written to the onboard
EEPROM. At
system boot, the PCIe-
69834
driver loads these
calibration con-stants, such that analog input path errors are
minimized.
JYTEK
provides a software API for calibrating the
PCIe-
69834
.
The onboard EEPROM provides two banks for calibration con-
stant storage. Bank 0, the default bank, records the factory cali-
brated constants, providing written protection preventing
erroneous auto-calibration. Bank 1 is user-defined space, pro-
vided for storage of self-calibration constants. Upon execution of
auto-calibration, the calibration constants are recorded to Bank 1.
When PCIe-
69834
boots, the driver accesses the calibration
con-stants and is automatically set to hardware. In the absence of
user
assignment, the driver loads constants stored in bank 0. If
con-stants from Bank 1 are to be loaded, the preferred bank
can be
designated as boot bank by software. Following re-
assignment of the bank, the driver will load the desired constants
on system re-boot. This setting is recorded to EEPROM and is
retained until re-configuration.
A.2 Auto-Calibration
Because errors in measurement and outputs will vary with time
and temperature, re-calibration is recommended when the module
is installed. Auto-calibration can measure and minimize errors
without external signal connections, reference voltages, or mea-
surement devices.
The PCIe-
69834
has an on-board calibration reference to
ensure the accuracy of auto-calibration. The reference voltage
is mea-sured on the production line and recorded in the
on-board
EEPROM.