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Configuration and Installation
Chapter 2
AT-MIO-64F-5 User Manual
2-26
© National Instruments Corporation
Single-Ended Connections for Grounded Signal Sources (NRSE Configuration)
If a grounded signal source is to be measured with a single-ended configuration, then the
AT-MIO-64F-5 must be configured in the NRSE input configuration. The signal is connected to
the positive (+) input of the AT-MIO-64F-5 PGIA and the signal local ground reference is
connected to the negative (-) input of the AT-MIO-64F-5 PGIA. The ground point of the signal
should therefore be connected to the AI SENSE pin. Any potential difference between the
AT-MIO-64F-5 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.
On the other hand, if the input circuitry of the AT-MIO-64F-5 is referenced to ground, such as in
the RSE input configuration, this difference in ground potentials appears as an error in the
measured voltage.
Figure 2-10 shows how to connect a grounded signal source to an AT-MIO-64F-5 board
configured for nonreferenced single-ended input. The AT-MIO-64F-5 analog input circuitry
must be configured for NRSE input configuration to make these types of connections.
Configuration instructions are included in Chapter 4,
Register Map and Descriptions.
ACH<0..63>
Input Multiplexer
Common-
Mode
Noise
AI GND
AI SENSE
V
s
V
cm
-
-
+
+
I/O Connector
AT-MIO-64F-5 Board in the NRSE Input Configuration
m
-
+
-
V
Measured
Voltage
PGIA
+
Ground-
Referenced
Signal
Source
Figure 2-10. Single-Ended Input Connections for Ground-Referenced Signals
Common-Mode Signal Rejection Considerations
Figures 2-7 and 2-10, located earlier in this chapter, show connections for signal sources that are
already referenced to some ground point with respect to the AT-MIO-64F-5. In these cases, the
PGIA can reject any voltage caused by ground potential differences between the signal source
and the AT-MIO-64F-5. In addition, with differential input connections, the PGIA can reject
common-mode noise pickup in the leads connecting the signal sources to the AT-MIO-64F-5.
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