National Instruments NI 783xR Manuel D’Utilisation

In DIFF input mode, the NI 783xR measures the difference between the 
positive and negative inputs. DIFF input mode is ideal for measuring 
ground-referenced signals from other devices. When using DIFF input 
mode, the input signal connects to the positive input of the instrumentation 
amplifier and its reference signal, or return, connects to the negative input 
of the instrumentation amplifier.

Use differential input connections for any channel that meets any of the 
following conditions:

•

The input signal is low level (less than 1 V).

•

The leads connecting the signal to the NI 783xR are greater than 
3 m (10 ft).

•

The input signal requires a separate ground-reference point or return 
signal.

•

The signal leads travel through noisy environments.

Differential signal connections reduce noise pickup and increase 
common-mode noise rejection. Differential signal connections also allow 
input signals to float within the common-mode limits of the 
instrumentation amplifier.

Figure 2-5 shows how to connect a ground-referenced signal source to a 
channel on the NI 783xR configured in DIFF input mode.