National Instruments BNC-2120 Installation Manual

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National Instruments BNC-2120 Installation Manual Manual pdf 6 page image

BNC-2120 Installation Guide 6 ni.comFigure 2. Measuring a Floating Signal SourceMeasuring Ground-Referenced SignalsTo measure ground-referenced signals, move the switch below the BNC connector for the AI channelyou are using to the GS position. Using the ground-referenced source switch position avoids groundloops, as shown in Figure 3. Refer to your DAQ device documentation for more information aboutmeasuring ground-referenced signals.Figure 3. Measuring a Ground-Referenced Signal SourceAI GND and AI SENSE signals are located at the analog input screw terminals of the BNC-2120. Whenconnecting signals to the screw terminals, use 28–16 AWG wire with the insulation stripped to 0.28 in.Measuring TemperatureYou can measure temperature on the BNC-2120 with the temperature reference and thermocoupleconnector.To use the integrated circuit (IC) temperature reference on the BNC-2120, move the BNC/Temp. Ref.switch above the AI 0 BNC to Temp. Ref. The integrated circuit (IC) temperature reference providesbuilt-in cold-junction compensation (CJC) through software. The IC sensor voltage is linearlyproportional to the sensor temperature where:°C = Volts × 100The sensor is accurate to ±1.5 °C.To use the thermocouple on the BNC-2120, move the BNC/Thermocouple switch above the AI 1 BNCto Thermocouple. You can connect any type of thermocouple with a two-prong miniature orsubminiature male connector to the thermocouple connector.+–SignalSource BNC-2120DAQ Device(Differential Input Mode)AI GND+–4.99 kΩFSFS Mode0.1 μF+–SignalSource BNC-2120DAQ Device(Differential Input Mode)AI GND+–4.99 kΩGSGS Mode0.1 μF