ADLINK PCIe-9852 - Manual (Page 39)

Calibration 29
PCIe-9852
Appendix A Calibration
This chapter introduces the calibration process to minimize analog
input measurement errors.
A.1 Calibration Constant
The PCIe-9852 is factory calibrated before shipment, with associ-
ated calibration constants written to the onboard EEPROM. At
system boot, the PCIe-9852 driver loads these calibration con-
stants, such that analog input path errors are minimized. ADLINK
provides a software API for calibrating the PCIe-9852.
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-9852 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-9852 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.