National Instruments NI PXI-7831R User Manual

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National Instruments NI PXI-7831R User Manual Manual pdf 35 page image

Chapter 2 Hardware Overview of the NI PXI-7831RNI PXI-7831R User Manual 2-14 ni.comcommon-mode signals as long as V+ in and V– in (input signals) are bothwithin their specified input ranges. Refer to Appendix A, Specifications,for more information about input ranges.Analog OutputThe NI PXI-7831R has eight 16-bit AO channels. The bipolar output rangeis fixed at ±10 V. Some applications require that the AO channels power-onto known voltage levels. To set the power-on levels, you can configure theNI PXI-7831R to automatically load and run your VI when the systempowers on. This VI can then set the AO channels to the desired voltagelevels. 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 AOchannel voltage output will be undefined.Connecting Analog Output SignalsThe AO signals are AO<0..7> and AOGND.AO<0..7> are the eight available AO channels. AOGND is the groundreference 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 MappingOutput Description AO VoltageInput Code (Hex)(Two’s Complement)Full-scale range –1 LSB 9.999695 7FFFFull-scale range –2 LSB 9.999390 7FFEMidscale 0.000000 0000Negative full-scale range,+1 LSB–9.999695 8001Negative full-scale range –10.000000 8000Any output voltage — AO Voltage10.0 V------------------------------- 32,768×