National Instruments AT-MIO-16X - Manual (Page 50)

Chapter 2 Configuration and Installation
AT-MIO-16X User Manual 2-28 © 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-16X must be configured in the NRSE
input configuration. The signal is connected to the positive (+) input of
the AT-MIO-16X PGIA and the signal local ground reference is
connected to the negative (–) input of the AT-MIO-16X PGIA. The
ground point of the signal should therefore be connected to the AI
SENSE pin. Any potential difference between the AT-MIO-16X 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-16X 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-16X board configured for nonreferenced single-ended input.
The AT-MIO-16X analog input circuitry must be configured for NRSE
input configuration to make these types of signals. Configuration
instructions are included in Chapter 4, Register Map and Descriptions.
Figure 2-10. Single-Ended Input Connections for Ground-Referenced Signals
ACH<0..15>
Input Multiplexer
Common-
Mode
Noise AI GND
AI SENSE
V
s
V
cm
-
-
+
+
I/O Connector AT-MIO-16X Board in the NRSE Input Configuration
m
-
+
- V
Measured
Voltage
PGIA
+
Ground-
Referenced
Signal
Source