National Instruments 6023E User Manual
Page 43
Chapter 4
Signal Connections
© National Instruments Corporation
4-13
Differential Connection Considerations (DIFF Input Configuration)
A DIFF 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 connected to the positive input of the PGIA, and its reference
signal, or return, is connected 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 signal.
Therefore, with a DIFF configuration for every channel, up to eight analog
input channels are available.
Use DIFF 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 device 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.
DIFF signal connections reduce picked up noise and increase
common-mode noise rejection. DIFF signal connections also allow input
signals to float within the common-mode limits of the PGIA.