Chapter4 ConnectingSignals
NI6013/6014 User Man ual 4-10 ni.com
Differential Connection Considerations
Adifferential connection is one in which the AI signal has its own reference
signal or signal return path. These connections are available when the
selectedchann el iscon figuredi n DIFF input mode. In DIFF mode, the AI
channelsare paired, with ACH<i> as the signal input and ACH<i+8> as the
signalreference. For example, ACH0 is paired with ACH8, ACH1 is paired
with ACH9, and so on. 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 DIFF input m ode, 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
AIchannels are available.
Youshould use DIFF input connections for any channel that meets any of
the followingconditi ons:
•The input signal is lowlevel (less than 1 V).
•The leads connecting the signal to the deviceare greater than
3m(10ft).
•The input signal requires a separate ground-reference point or return
signal.
•The signal leads travelthrough noisy environments.
Differentialsignal connections reduce noise pick up and increase
common-modenoise rejection. Differentialsignal connections also allow
input signals to float within the common-mode limits of the PGIA.