National Instruments DAQCard-1200 User Manual
Page 30
Chapter 3
Signal Connections
3-8
© National Instruments Corporation
When you configure the DAQCard-1200 for DIFF input, each signal uses
two of the multiplexer inputs—one for the signal and one for its reference
signal. Therefore, only four analog input channels are available when using
the DIFF configuration. You should use the DIFF input configuration when
any of the following conditions is present:
•
Input signals are low level (less than 1 V).
•
Leads connecting the signals to the DAQCard-1200 are greater
than 15 ft.
•
Any of the input signals 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 signal and noise rejection. With these connections, input
signals can float within the common-mode limits of the input
instrumentation amplifier.
Differential Connections for Grounded Signal Sources
Figure 3-3 shows how to connect a ground-referenced signal source to a
DAQCard-1200 configured for DIFF input. Refer to the
section in Chapter 2,
Installation and Configuration
, for
configuration instructions.