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AC/DC wall adapter, it may be ground referenced, depending on the
connection. You should determine from the computer documentation
whether any of the power connections are tied to the building power
system ground.
Ground-Referenced Measurement System
A ground-referenced measurement system is one that is connected in some
way to the building system ground. Instruments that plug into the building
power system fall into this category.
Floating Measurement System
A floating, or nonreferenced, measurement system is one that is not
connected in any way to the building ground system but rather has an
isolated ground-reference point. Some examples of floating measurement
systems are battery-powered instruments, instruments powered with a
nonground-referenced power adapter, and instruments with differential
inputs. A floating measurement system will float to the level of the signals
being measured.
Input Configurations
To measure different types of input signals, you can configure the
DAQCard-700 for one of two input modes—DIFF or RSE. These
two modes can be implemented by changing the configuration of the
instrumentation amplifier onboard the DAQCard-700. Figure 3-2 shows
a diagram of the DAQCard-700 instrumentation amplifier.
V +
in
V -
in
Figure 3-2. DAQCard-700 Instrumentation Amplifier
Instrumentation
+
Amplifier
_
V = [ V +
in
3-5
Chapter 3
Connecting Signals
Measured
V
Voltage
– V -
] GAIN
in
DAQCard-700 User Manual
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