National Instruments NI 784xR User Manual

Also see for NI 781xR: User manual User manual

Contents

National Instruments NI 784xR User Manual Manual pdf 31 page image

Chapter 2 Hardware Overview of the NI 78xxRR Series Intelligent DAQ User Manual 2-10 ni.comDifferential Connection Considerations (DIFF Input Mode)In DIFF input mode, the NI 783xR/784xR/785xR measures the differencebetween the positive and negative inputs. DIFF input mode is ideal formeasuring ground-referenced signals from other devices. When usingDIFF input mode, the input signal connects to the positive input of theinstrumentation amplifier and its reference signal, or return, connects to thenegative input of the instrumentation amplifier.Use differential input connections for any channel that meets any of thefollowing conditions:• The input signal is low level (less than 1 V).• The leads connecting the signal to the NI 783xR/784xR/785xR aregreater than 3 m (10 ft).• The input signal requires a separate ground-reference point or returnsignal.• The signal leads travel through noisy environments.Differential signal connections reduce noise pickup and increasecommon-mode noise rejection. Differential signal connections alsoallow input signals to float within the common-mode limits of theinstrumentation amplifier.