National Instruments NI 4350 User Manual

Also see for NI 4350: User manual

Contents

National Instruments NI 4350 User Manual Manual pdf 32 page image

Chapter 3 NI 4350 Operation©National Instruments Corporation3-11NI 4350 User Manualtemperature) and at the cold-junction on the accessory will introduceerror.To minimize thermal EMFs, use wires of the same thermocoupletype when extending the length of the thermocouple. Also, minimizetemperature gradients in the space enclosing the thermocouple, theNI 4350 instrument, and its accessories.Measuring DC VoltageConnecting Your DC Voltage SignalThe NI 4350 accessories—the CB-27T and CB-27 for the NI 4350(PCMCIA), and the TBX-68T and TBX-68 for the NI 4350 (ISA) andthe NI 4350 (USB)—are designed to be used with any DC voltagesignal. Consult your accessory installation guide for instructions onhow to connect your voltage signals.The NI 4350 analog inputs are protected against damage from voltageswithin ±42 VDC in all ranges when powered up and ±17 VDC when theNI 4350 instrument is powered down. You should never apply voltagesabove these levels to the inputs.Caution: To prevent possible safety hazards, the maximum voltage between any ofthe analog inputs and the computer ground should never exceed ±42 VDCwhen the NI 4350 instrument is powered up and ±17 VDC when theNI 4350 instrument is powered down.Input RangesYour NI 4350 instrument has six bipolar input ranges available formeasuring DC voltage. These ranges are ±625 mV, ±1.25 V, ±2.5 V,±3.75 V, ±7.5 V, and ±15 V. The NI 4350 instrument can measure DCvoltage to the specified accuracy as long as the voltage is within theselected input range. To get the best resolution, noise rejection, andaccuracy, choose the smallest possible range. Make sure that eachsignal input to CH+ and CH– is within the input common mode limitsof this input range. The input common mode limits are ±2.5 V and±15 V for the lower three and higher three input ranges, respectively.!