National Instruments 3.21E+04 Manual De Usuario

Chapter 4     Signal Connections

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 National Instruments Corporation

4-25

AT-MIO/AI E Series User Manual

Figure 4-8 shows how to connect a floating signal source to an 
AT E Series board channel configured for RSE mode.

Figure 4-8.  Single-Ended Input Connections for Nonreferenced or Floating Signals

To measure a grounded signal source with a single-ended configuration, 
you must configure your AT E Series board in the NRSE input 
configuration.  The signal is then connected to the positive input of the 
AT E Series PGIA, and the signal local ground reference is connected 
to the negative input of the PGIA.  The ground point of the signal 
should, therefore, be connected to the AISENSE pin.  Any potential 
difference between the AT E Series ground and the signal ground 
appears as a common-mode signal at both the positive and negative 
inputs of the PGIA, and this difference is rejected by the amplifier.  If 
the input circuitry of an AT E Series board were referenced to ground, 
in this situation as in the RSE input configuration, this difference in 
ground potentials would appear as an error in the measured voltage.

V

s

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+

+

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V

m

Measured

Voltage

Floating

Signal

Source

ACH<0..15>

AIGND

Instrumentation

Amplifier

I/O Connector

AISENSE

Selected Channel in RSE Configuration

PGIA

Input Multiplexers