EMI Symptoms - Electronic Equipment

Electronic devices can be very susceptible to both radiated and conducted EMI noise. Such electrical noise contains very high frequencies that can disrupt a device's internal data flow, and corrupt data on data cables between devices.

Most electronic equipment has an EMI filter on the front end of the power supply. Required by the FCC, this filter stops most noise conducted from power lines through the power supply. However, noise can find other paths into the device.

EMI may be radiated, and can couple into the system through the metallic enclosures or through the data lines. This is especially likely if there is an inadequate ground or cable is unshielded or improperly terminated.

Conducted noise can still enter the system through the ground. If the ground wire contains electrical signals, they do not mysteriously disappear. They will travel the path of least resistance and sometimes return to their point of origin, a device, ground, or even earth.