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3.5 Field Wiring Considerations
•
When
you use USB-4761 to
acquire data
from outside,
noises
in the
environment might
significantly affect
the accuracy
of your measure-
ments
if due cautions are not
taken.
The following
measures will be
helpful to
reduce possible interference running signal
wires between
signal sources and
the
USB-4761.
•
The signal
cables
must be kept
away
from strong electromagnetic
sources such as
power lines, large
electric motors, circuit breakers or
welding machines,
since
they may
cause strong electromagnetic inter-
ference. Keep the
analog signal cables away from
any
video monitor,
since it can significantly
affect a data acquisition system.
•
If the cable travels through an
area
with significant electromagnetic
interference, you should
adopt individually shielded, twisted-pair wires
as the analog input cable.
This
type of cable
has its signal
wires twisted
together and
shielded with a metal
mesh.
The metal mesh should only
be
connected
to one point at the signal source ground.
•
Avoid running the signal cables
through
any conduit that
might have
power
lines in it.
•
If you
have
to place your
signal cable parallel to a power
line that
has a
high
voltage
or high current running through it, try
to keep a
safe
dis-
tance
between them.
Or place the
signal cable in
a right angle
to the
power line
to minimize
the undesirable
effect.
USB-4761 User Manual 26