National Instruments NI 4350 User Manual

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Contents

National Instruments NI 4350 User Manual Manual pdf 22 page image

©National Instruments Corporation3-1NI 4350 User ManualChapter3NI 4350 OperationThis chapter describes how to use your NI 4350 instrument and includesoperation tips on taking measurements with temperature sensors such asthermocouples, RTDs, and thermistors, as well as measuring voltagesand resistances.Warming up Your NI 4350 InstrumentTo minimize the effects of thermal drift and to ensure the specifiedaccuracy, allow the NI 4350 instrument to warm up for at least10 minutes after power-up before taking measurements. To maximizethe relative accuracy of measurements, take all measurements after yourNI 4350 instrument warms up for about 30 minutes.Choosing a Measurement ModeEach analog input channel can be configured in two possiblemeasurement modes — the volts mode or the 4-wire ohms mode. Use thevolts mode for thermocouple and voltage measurements and the 4-wireohms mode for RTD, thermistor, and resistance measurements using thebuilt-in current source to provide excitation for your resistive sensors.In the 4-wire ohms mode, the software will return the resistance valueby dividing the voltage measured by the value of the current sourcestored onboard.Note: VirtualBench, the NI435X instrument driver, and the DAQ ChannelWizard select the measurement mode automatically, depending on thesensor type you specify.Choosing a RangeThe volts mode has six bipolar input ranges: ±625 mV, ±1.25 V,±2.5 V, ±3.75 V, ±7.5 V, and ±15 V.