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Chapter 5
Calibration Procedures
Input Range
Calibration Voltage
-10 to +10 V
-5 to +5 V
-9.99756 V
-4.99878 V
a. Connect the calibration voltage across ACH0 (pin 3 on the I/O connector) and ACH8 (pin 4).
Connect the ground point on the calibration voltage source to AI SENSE (pin 19).
b. Take analog input readings from channel 0 at a gain of 1, and adjust trimpot R6 until the
ADC readings flicker evenly between -2,048 and -2,047.
3. Adjust the analog input gain.
Adjust the analog input gain by applying an input voltage across ACH0 and ACH8. This input
voltage is V+fs - 3/2 LSB and depends on the input range selected:
Input Range
Calibration Voltage
-10 to +10 V
-5 to +5 V
+9.99268 V
+4.99634 V
a. Connect the calibration voltage across ACH0 (pin 3 on the I/O connector) and ACH8 (pin 4).
Connect the ground point on the calibration voltage source to AI SENSE (pin 19).
b. Take analog input readings from channel 0 at a gain of 1, and adjust trimpot R1 until the
ADC readings flicker evenly between 2,046 and 2,047.
Unipolar Input Calibration Procedure
If your board is configured for unipolar input, which provides an input range of 0 to +10 V, then
complete the following procedure in the order given. This procedure assumes that ADC readings
are in the range 0 to +4,095.
1. Adjust the amplifier input offset.
To adjust the amplifier input offset, follow these steps:
a. Connect both ACH0 (pin 3 on the I/O connector) and ACH8 (pin 4) to AI SENSE (pin 19).
© National Instruments Corporation
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AT-MIO-16D User Manual