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Chapter 6
Regular and proper calibration procedures ensure the maximum
possible accuracy. It is easy to complete the A/D calibration proce-
dure automatically (i.e. through software calibration) by executing the
A/D calibration program AutoCali. Therefore, it is not necessary to
adjust the hardware settings of the PCI-1712/1712L. However, the
following calibration steps are also provided for your reference in case
manual calibration is needed:
1. Adjust VR1 until the reference voltage on TP5 has reached
+5.0000 V.
2. Set PCI-1712 to calibration mode, which will configure AI2 to +5
V, and AI0 to 0 V. (Write "1" in AI0_CAL at the register address
BASE+6 bif7).
3. Adjust the PGA offset voltage. First, set the analog input voltage
range of AI0 to ±10V. Adjust the PGA offset register (BASE+2C),
and acquire a value from AI0 in single value acquisition mode.
Then switch the analog voltage range to ±1.25V to repeat the
operation in this step again to acquire a value from AI0. Repeat
this cycle several times. Meanwhile, adjust the PGA offset
voltage until the AI0's values become the same for both the
analog input range ±10 V and ±1.25 V.
4. Adjust the gain value of the PGA. First, set the analog input
voltage range of AI2 between 0 and 5V. Adjust the gain register
(Base+2C), and then acquire the value for AI2 from single value
acquisition mode. Adjust the gain value of the PGA until the
subsequent AI2's values converge within the Ox0ffe to
Ox0fff range.
5. Adjust the bipolar offset voltage. First, set the analog input
range within ±2.5 V. Adjust the bipolar offset register (Base+2C),
and then acquire the code from AI0 from single value acquisition
mode. Adjust the bipolar offset voltage until the AI0's code
flickers around Ox0800.
6. Adjust unipolar offset voltage. First, set the analog input range
within 0 and 5 V. Adjust the unipolar offset register (Base+2C),
and then acquire the code for AI0 from single value acquisition
PCI-1712/1712L User's Manual
– 56 –
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