Common-Mode Signal Rejection Considerations; Analog Output - National Instruments PXI-7811 User Manual

Chapter 2 Hardware Overview of the NI 78xxR

Common-Mode Signal Rejection Considerations

Figure 2-6 and Figure 2-9 show connections for signal sources that
are already referenced to some ground point with respect to the
NI 783xR/784xR/785xR. In these cases, the instrumentation amplifier can
reject any voltage caused by ground potential differences between the
signal source and the device. With differential input connections, the
instrumentation amplifier can reject common-mode noise pickup in the
leads connecting the signal sources to the device. The instrumentation
amplifier can reject common-mode signals when V+
(input signals) are both within their specified input ranges. Refer to
the NI R Series Multifunction RIO Specifications, available at
manuals

Analog Output

The bipolar output range of the NI 783xR/784xR/785xR AO channels 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 783xR/784xR/785xR to load and run a VI when the system powers on.
The VI can set the AO channels to the desired voltage levels. The VI
interprets data written to the DAC in two's complement format. Table 2-3
shows the ideal AO voltage generated for a given input code.
Table 2-3. Ideal Output Voltage and Input Code Mapping
Output Description
Full-scale range –1 LSB
Full-scale range –2 LSB
Midscale
Negative full-scale range, +1 LSB
Negative full-scale range
Any output voltage
If your VI does not set the output value for an AO channel, then the AO channel
Note
voltage output will be undefined.
R Series Multifunction RIO User Manual
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
, for more information about input ranges.
AO Voltage
9.999695
9.999390
0.000000
–9.999695
–10.000000
—
2-16
and V–
in in
ni.com/
Input Code (Hex)
(Two's Complement)
7FFF
7FFE
0000
8001
8000
AO Voltage
×
------------------------------ -
32,768
10.0 V
ni.com