ICS PCI-AOB2 Series, User Manual

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Calibration 7-1
Chapter 7
Calibration
Overview
Periodic calibration of the PCI-AOB2/4/6 Series cards is recommended if they are used in
extreme environmental conditions. The cards use very stable components but high-low
temperature cycles might result in slight analog output errors.
This card is calibrated by software using the following formula:
Y= (4096 -a - b)/4096) * X + b
To calibrate the card, run the calibration program and follow the screen prompts. No
attempt at calibration should be made in noisy locations or with a noisy calibration setup.
The calibration program stores various data to the card to facilitate calibrating the data
output in a run-time environment. The data collected during calibration is stored in an
EEPROM located at the second of the I/O base addresses assigned to the device
(
BaseAddresses[3] in the PCI_COMMON_CONFIG structure
). The
EEPROM contains two values per channel per range. The ZERO (or OFFSET) and the
SPAN calibration constants are stored (a and b from the equation above) for each channel
at each possible range (0-6). These constants are used during normal operation to
calibrate the output data in real-time. Refer to the samples provided on disk for an
example of using this data.
In addition to 'a' and 'b' as shown above, the EEPROM contains a table of ranges assigned
to each channel. Starting at Base+F0, 6 base addresses contain one byte each, from 0-6,
indicating the voltage output range assigned to that channel. It is important to use the
calibration program at least once if the default range (+/- 10V) is changed on any channel,
to allow this table of data to be reconfigured. If this data is incorrect, calibration is not
guaranteed.