Chapter 2
Configuration and Installation
© National Instruments Corporation
2-25
AT-MIO-64F-5 User Manual
The AT-MIO-64F-5 can be software configured for two different types of single-ended
connectionsÐRSE configuration and NRSE configuration. The RSE configuration is used for
floating signal sources; in this case, the AT-MIO-64F-5 provides the reference ground point for
the external signal. The NRSE input configuration is used for ground-referenced signal sources;
in this case, the external signal supplies its own reference ground point and the AT-MIO-64F-5
should not supply one.
In single-ended configurations, more electrostatic and magnetic noise couples into the signal
connections than in differential configurations. Moreover, the amount of coupling varies among
channels, especially if a ribbon cable is used. The coupling is the result of differences in the
signal path. Magnetic coupling is proportional to the area between the two signal conductors.
Electrical coupling is a function of how much the electric field differs between the two
conductors. Referring to the MIO subconnector, for example, if AI GND is used as the signal
reference, Channels 0 and 8 are the quietest and Channels 7 and 15 are the noisiest. AI GND is
on pins 1 and 2, which are very close to pins 3 and 4, which are Channels 0 and 1. On the other
hand, Channels 7 and 15 are on pins 17 and 18, which are the farthest analog inputs from
AI GND. The sensitivities to noise of the other channels in the middle are between those of
Channels 0 and 15 and vary according to their distance from AI GND. If AI SENSE is used as a
reference instead of AI GND, the sensitivity to noise still varies among the channels, but in this
case according to their distance from AI SENSE, pin 19 (so Channel 15 is the least sensitive and
Channel 0 is the most sensitive).
Single-Ended Connections for Floating Signal Sources (RSE Configuration)
Figure 2-9 shows how to connect a floating signal source to an AT-MIO-64F-5 board configured
for single-ended input. The AT-MIO-64F-5 analog input circuitry must be configured for RSE
input to make these types of connections. Configuration instructions are included in Chapter 4,
Register Map and Descriptions.
ACH<0..63>
Input Multiplexer
AI GND
AI SENSE
V
s
-
+
I/O Connector
AT-MIO-64F-5 Board in the RSE Input Configuration
m
-
+
-
V
Measured
Voltage
PGIA
+
Nonreferenced
or Floating
Signal
Source
Gain
Figure 2-9. Single-Ended Input Connections for Nonreferenced or Floating Signals
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