Advantech 4718 user manual Field Wiring Considerations, Isolated Digital Input Channel Connections

Figure 3.4: Isolated Digital Input Channel Connections

3.6Field Wiring Considerations

•When you use USB-4718 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-4718.

•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.

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