NI DAQ 6052E, Руководство пользователя

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Chapter 4 Connecting the Signals
© National Instruments Corporation 4-13 NI 6052E User Manual
Differential Connections (DIFF Input Mode)
A differential connection is one in which the DAQPad-6052E AI 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 DIFF input, each signal uses two
multiplexer inputs—one for the signal and one for its reference. Therefore,
with a DIFF configuration for every channel, as many as eight AI channels
are available.
In DIFF input mode, the AI channels are paired, with ACH< i > as the signal
input and ACH< i +8> as the signal reference. For example, ACH0 is paired
with ACH8, ACH1 is paired with ACH9, and so on.
Use DIFF input connections for channels that meet any of the following
conditions:
• The input signal is low-level (less than 1 V).
• The leads connecting the signal to the DAQPad-6052E 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 PGIA.