Chapter 2
Installing and Configuring the DAQPad-MIO-16XE-50
DAQPad-MIO-16XE-50 User Manual
2-6
ni.com
Note
You can calibrate the AI circuitry for either a unipolar or bipolar polarity. If you mix
unipolar and bipolar channels in the scan list and you are using NI-DAQ, NI-DAQ will load
the calibration constants appropriate to the polarity for which analog input channel 0 is
configured.
Considerations for Selecting Input Ranges
Which input polarity and range you select depends on the expected range
of the incoming signal. A large input range can accommodate a large signal
variation but reduces the voltage resolution. Choosing a smaller input range
improves the voltage resolution but may result in the input signal going out
of range. For best results, you should match the input range as closely as
possible to the expected range of the input signal. For example, if you are
certain the input signal is not negative (below 0 V), unipolar input polarity
is best. However, if the signal is negative or equal to zero, inaccurate
readings occur if you use unipolar input polarity.
Dither
The addition of dither adds approximately 0.5 LSB
rms
of white Gaussian
noise to the signal to be converted by the ADC. This addition is useful
for applications involving averaging to increase the resolution of the
DAQPad-MIO-16XE-50, as in calibration or spectral analysis. In such
applications, noise modulation is decreased and differential linearity is
improved by the addition of the dither. When taking DC measurements,
such as when checking the board calibration, average about 1,000 points to
take a single reading. This process removes the effects of quantization and
Table 2-2.
Actual Range and Measurement Precision for the DAQPad-MIO-16XE-50
Range Configuration
Gain
Actual Input Range
Precision
1
0 to +10 V
1.0
2.0
10.0
100.0
0 to +10 V
0 to +5 V
0 to +1 V
0 to 100 mV
152.59 µV
76.29 µV
15.26 µV
1.53 µV
–10 to +10 V
1.0
2.0
10.0
100.0
–10 to +10 V
–5 to +5 V
–1 to +1 V
–100 to +100 mV
305.18 µV
152.59 µV
30.52 µV
3.05 µV
1
The value of 1 LSB of the 16-bit ADC; that is, the voltage increment corresponding to a change of 1 count in the ADC
16-bit count.
Note:
Refer to Appendix A,
, for absolute maximum ratings.
