Field Wiring Considerations - Advantech USB-4750 User Manual

3.4

Field Wiring Considerations

When you use USB-4750 to acquire data from outside, noises in the environ-

ment might significantly affect the accuracy of your measurements if due cau-
tions are not taken. The following measures will be helpful to reduce possible
interference running signal wires between signal sources and the USB-4750.
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 interference. Keep the analog sig-
nal 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 sig-
nal 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 distance between
them. Or place the signal cable in a right angle to the power line to minimize the
undesirable effect.
Figure 3.3 Isolated Digital Output Connections
13 USB-4750 User Manual