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Chapter 2
Analog Input
Field Wiring Considerations
E Series User Manual
I/O Connector
Ground-
+
Referenced
V
s
Signal
–
Source
Common-
+
Mode
V
Noise
cm
–
and Ground
Potential
Figure 2-12. Single-Ended Connections for Grounded Signal Sources
Environmental noise can seriously affect the measurement accuracy of the
device if you do not take proper care when running signal wires between
signal sources and the device. The following recommendations apply
mainly to AI signal routing to the device, although they also apply to signal
routing in general.
Minimize noise pickup and maximize measurement accuracy by taking the
following precautions:
•
Use DIFF AI connections to reject common-mode noise.
•
Use individually shielded, twisted-pair wires to connect AI signals to
the device. With this type of wire, the signals attached to the positive
and negative input channels are twisted together and then covered with
a shield. You then connect this shield only at one point to the signal
source ground. This kind of connection is required for signals traveling
through areas with large magnetic fields or high electromagnetic
interference.
Refer to the NI Developer Zone document, Field Wiring and Noise
Considerations for Analog Signals, for more information.
AI <0..15>
Input Multiplexers
AI SENSE
AI GND
E Series Device Configured in NRSE Mode
(NRSE Configuration)
2-28
Instrumentation
Amplifier
+
+
PGIA
Measured
–
V m
Voltage
–
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