Chapter4 ConnectingSignals
©NationalInstruments Corporation 4-55 ATE Series User Manual
Field Wiring Considerations
Environmentalnoise can seriously affect the accuracy of measurements
made with the AT E Series device if you do not take proper care when
runningsignal wires between signal sources andthe device. The following
recommendationsapply mainly to AI signal routing to the device, although
they also apply to signal routing in general.
Youcan minimize noise pickup and maximize measurement accuracy by
taking thefollowing precautions:
•Use differentialanalog input connect ions to reject common-mode
noise.
•Use individuallyshielded, twisted -pair wires toc onnect AI signals to
thedevice. With this type of wire, the signals attached to the CH+ and
CH–inputs are twisted together and then coveredwith a shield. You
thenco nnect this shield only at one point to the signal source ground.
Thiskind of connection is required for signals traveling through areas
with largemagneti c fieldsor high electromagnetic interference.
•Routesignals to the device carefully. Keep cabling away from noise
sources. The most common noise source in a PC DAQsystem is the
video monitor.Separate the monitor from the analog signals as much
aspossible.
The followingrecommendations apply f or all signal connections to the
ATE Series device:
•Separate ATE Series device signal lines from high-current or
high-voltagelines. These lines are capable of inducing currents in or
voltageson the AT E Series device signal lines if they run in parallel
pathsat a close distance. To reduce the magnetic coupling between
lines,separate them by a reasonable distance if they run in parallel,
orrun the lines at right angles to each other.
•Donot run sig nal lines through conduits that also contain power lines.
•Protectsignal lines from magnetic fields caused by electric motors,
weldingequipment, breakers, or transformers by running them through
special metal conduits.
Formore information, refer to the NI Developer Zone tutorial, Field Wiring
and Noise Consideration for Analog Signals,at
ni.com/zone.