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Chapter 4 Signal Connections
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National Instruments Corporation 4-13 PCI-6023E/6024E/6025E User Manual
Differential Connection Considerations (DIFF Input Configuration)
A differential connection is one in which the analog input signal has its own
reference signal or signal return path. These connections are available
when the selected channel 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 configure a channel for differential input, each signal uses two
multiplexer inputs—one for the signal and one for its reference signal.
Therefore, with a differential configuration for every channel, up to eight
analog input channels are available.
You should 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 board are greater than
10 ft (3 m).
• The input signal requires a separate ground-reference point or return
signal.
• The signal leads travel through noisy environments.
Differential signal connections reduce picked up noise and increase
common-mode noise rejection. Differential signal connections also allow
input signals to float within the common-mode limits of the PGIA.
PCI.book Page 13 Wednesday, September 16, 1998 9:09 AM