Chapter4 ConnectingSignals
ATE Series User Manual 4-20 ni.com
Differential Connection Considerations (DIFF Input Configuration)Adifferential connection is one in whichthe AT E Series device AI signal
has its own reference signal or signal return path. These connections are
available when the selectedchannel is configured in DIFF input mode.
The input signal is tied to the positive input of the PGIA, and its reference
signal,or return, is tied to the negative input of the PGIA.
When you configurea channel for differential input, each signal uses two
multiplexerinputs—one for the signal and one for its reference signal.
Therefore,with a differential configuration for every channel, up to eight
AIchan nels are available(up to 32 channels on the AT-MIO-64E-3).
InDIFF input mode, the AI channels are paired, with ACH<i> as the signal
inputand ACH<i+8> as the signal reference. For example, ACH0 is paired
withACH8,ACH1ispairedwithACH9,andsoon.
Youshould use differential input connections for any channel that meets
anyof the following conditions:
•The input signal is lowlevel (less than 1 V).
•The leads connecting the signal to the ATE Series device are greater
than 10 ft (3 m).
•The input signal requires a separate ground-reference point or return
signal.
•The signal leads travelthrough noisy environments.
Differentialsignal connections reduce picked-up noise and increase
common-modenoise rejection. Differentialsignal connections also allow
input signals to float within the common-mode limits of the PGIA.