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Chapter 2
Analog Input
Differential Connections for Non-Referenced or Floating Signal Sources
+
Ground-
Referenced
V s
Signal
Source
–
Bias
Current
Return
Paths
I/O Connector
E Series User Manual
With this type of connection, the PGIA rejects both the common-mode
noise in the signal and the ground potential difference between the signal
source and the device ground, shown as V
Common-Mode Signal Rejection Considerations
Ground-referenced signal sources with differential connections to the
device are referenced to some ground point with respect to the device. In
this case, the PGIA can reject any voltage caused by ground potential
differences between the signal source and the device. In addition, with
DIFF input connections, the PGIA can reject common-mode noise pickup
in the leads connecting the signal sources to the device. The PGIA can
reject common-mode signals as long as AI + and AI – (input signals) are
both within ±11 V of AI GND.
Figure 2-10 shows how to connect a floating signal source to a channel
configured in DIFF mode.
AI +
Bias
Resistors
(see text)
AI –
Input Multiplexers
AI SENSE
AI GND
Figure 2-10. Connecting a Floating Signal Source to a DIFF Mode Channel
cm
E Series Device Configured in DIFF Mode
2-24
in this figure.
Instrumentation
Amplifier
+
PGIA
+
Measured
–
V m
Voltage
–
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