Calibration Procedures
Chapter 5
AT-MIO-16D User Manual
5-4
© National Instruments Corporation
Board Configuration
Calibration procedure differs depending on input ranges and input configuration modes selected.
Two analog input calibration procedures are given below: one for the two bipolar input
configurations (-10 to +10 V and -5 to +5 V), and one for the unipolar input configuration
(0 to +10 V).
The calibration procedures presented here assume that your AT-MIO-16D board is configured
for DIFF input. If necessary, reconfigure your board for DIFF input before using the following
calibration procedures.
To calibrate your board with a nondifferential input setting, the procedure is similar to the
procedures outlined below with the following exception: the procedures given below apply the
input calibration voltages across the positive (+) and negative (-) inputs for DIFF channel 0. For
single-ended input, apply your calibration voltages between the channel 0 positive (+) input and
whichever ground system you are using (refer to Chapter 2, Configuration and Installation, for
instructions on using single-ended input connections).
Bipolar Input Calibration Procedure
If your board is configured for bipolar input, which provides the ranges -5 to +5 V or
-10 to +10 V, then complete the following procedure in the order given. This procedure assumes
that ADC readings are in the range -2,048 to +2,047.
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).
b. Take analog input readings from channel 0 at the following gains:
both 1 and 500 for the AT-MIO-16DL
both 1 and 8 for the AT-MIO-16DH
c. Adjust trimpot R2 until the readings match to within one count at both gain settings.
2. Adjust the ADC input offset.
Adjust the ADC input offset by applying an input voltage across ACH0 and ACH8. This input
voltage is V-
fs
+
1
/
2
LSB and depends on the input range selected:
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