User manual

Page 8-1
Manual MPCI-DA12-16.Dh
Chapter 8: Calibration
Periodic calibration of the PCI-DA12-8/16 cards is recommended if they are used in extreme
environmental conditions. The card uses 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, 16 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.
Word Address Range Offset
(‘b’ in formula)
Span
(‘a’ in formula)
Base + 00h
to
Base + 1Eh
0 to +5 V.
DAC 0
to
DAC 15
DAC 0
to
DAC 15
Base + 20h
to
Base + 3Eh
0 to +2.5 V.
DAC 0
to
DAC 15
DAC 0
to
DAC 15
Base + 40h
to
Base + 5Eh
0 to +10 V.
DAC 0
to
DAC 15
DAC 0
to
DAC 15
Base + 60h
to
Base + 7Eh
-5 V to +5 V.
DAC 0
to
DAC 15
DAC 0
to
DAC 15