National Instruments NI 7831R User Manual

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National Instruments NI 7831R User Manual Manual pdf 23 page image

Chapter 2 Hardware Overview of the NI 7831RNI 7831R User Manual 2-4 ni.comInput ModesThe NI 7831R input mode is software configurable. The input channelssupport three input modes—differential (DIFF), referenced single-ended(RSE), and nonreferenced single-ended (NRSE). The selected input modeapplies to all the input channels. Table 2-2 describes the three input modes.Input RangeThe NI 7831R AI range is fixed at ±10 V.Table 2-1. Ideal Output Code and AI Voltage MappingInput Description AI VoltageOutput 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 input voltage —Table 2-2. Available Input Modes for the NI 7831RInput Mode DescriptionDIFF When the NI 7831R is configured in DIFF input mode, each channel uses twoAI lines. The positive input pin connects to the positive terminal of the onboardinstrumentation amplifier. The negative input pin connects to the negative inputof the instrumentation amplifier.RSE When the NI 7831R is configured in RSE input mode, each channel uses only itspositive AI pin. This pin connects to the positive terminal of the onboardinstrumentation amplifier. The negative input of the instrumentation amplifierconnects internally to the AI ground (AIGND).NRSE When the NI 7831R is configured in NRSE input mode, each channel uses onlyits positive AI pin. This pin connects to the positive terminal of the onboardinstrumentation amplifier. The negative input of the instrumentation amplifier oneach AI channel connects internally to the AISENSE input pin.Output Code32,768---------------------------------- 10.0 V×