B&B Electronics USB-4751/4751L user manual Field Wiring Considerations

3.4 Field Wiring Considerations

•When you use USB-4751/4751L to acquire data from outside, noises in the environment might significantly affect the accuracy of your mea- surements 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-4751/4751L.

•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.

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