National Instruments NI 783xR User Manual

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National Instruments NI 783xR User Manual Manual pdf 23 page image

Chapter 2 Hardware Overview of the NI 783xRNI 783xR User Manual 2-4 ni.comInput RangeThe NI 783xR AI range is fixed at ±10 V.Connecting Analog Input SignalsThe AI signals for the NI 783xR are AI<0..n>+, AI<0..n>–, AIGND, andAISENSE. For the NI 7830R, n=4. For the NI 7831R/7833R, n=8. TheAI<0..n>+ and AI<0..n>– signals are connected to the eight AI channels ofthe NI 783xR. For all input modes, the AI<0..n>+ signals are connected tothe positive input of the instrumentation amplifier on each channel. Thesignal connected to the negative input of the instrumentation amplifierdepends on how you configure the input mode of the device.In differential input mode, signals connected to AI<0..n>– are routed to thenegative input of the instrumentation amplifier for each channel. In RSEinput mode, the negative input of the instrumentation amplifier for eachchannel is internally connected to AIGND. In NRSE input mode, theAISENSE signal is connected internally to the negative input of theinstrumentation amplifier for each channel. In DIFF and RSE input modes,AISENSE is not used.Caution Exceeding the differential and common-mode input ranges distorts the inputsignals. Exceeding the maximum input voltage rating can damage the NI 783xR and thecomputer. NI is not liable for any damage resulting from such signal connections. Themaximum input voltage ratings are listed in Table B-2, NI 783xR I/O Signal Summary.AIGND is a common AI signal that is routed directly to the ground tie pointon the NI 783xR. You can use this signal for a general analog ground tiepoint to the NI 783xR if necessary.Connection of AI signals to the NI 783xR depends on the input mode of theAI channels you are using and the type of input signal source. Withdifferent input modes, you can use the instrumentation amplifier indifferent ways. Figure 2-3 shows a diagram of the NI 783xRinstrumentation amplifier.