National Instruments 3.21E+04 Manual De Usuario

Chapter 4     Signal Connections

AT-MIO/AI E Series User Manual

4-20

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 National Instruments Corporation

A differential connection is one in which the AT E Series board 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 (up to 32 channels on the 
AT-MIO-64E-3).  

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 AT E Series 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.