Chapter 2 Hardware Overview ofthe NI PXI-7831R
NI PXI-7831R User Manual 2-14 ni.com
common-mode signals as long as V+in and V–in (input signals) are both
within their specified input ranges. Refer to Appendix A, Specifications,
for more information about input ranges.
Analog Output
The NIPXI-783 1R has eight 16-bit AO channels. The bipolar output range
is fixed at ±10 V. Some applications require that the AO channels power-on
to known voltage levels. To set the power-on levels, you can configure the
NI PXI-7831R to automatically load and run your VI when the system
powers on. This VI can then set the AO channels to the desired voltage
levels. Data written to the DAC is interpreted in two’s complement format.
Table 2-3 shows the ideal AO voltage generated for a given input code.
Note If the output value for an AO channel is not specifically set by your VI then the AO
channel voltage output will be undefined.
Connecting Analog Output Signals
The AO signals are AO<0..7> and AOGND.
AO<0..7> are the eight available AO channels. AOGND is the ground
reference signal for the AO channels.
Figure 2-9 shows how to make AO connections to the NI PXI-7831R.
Table 2-3. Ideal Output Voltage and Input Code Mapping
Output Description AO Voltage
Input Code (Hex)
(Two’sComplement)
Full-scale range –1LSB 9.999695 7FFF
Full-scale range –2LSB 9.999390 7FFE
Midscale 0.000000 0000
Negative full-scale range,
+1 LSB
–9.999695 8001
Negative full-scale range –10.000000 8000
Any output voltage —AO Voltage
10.0 V
-------------------------------32,768×