The source of human interference refers to the electromagnetic interference generated by electrical and electronic equipment and other artificial devices. The human interference sources mentioned here refer to the unconscious interference. As for in order to achieve a certain purpose and intentionally cast interference, such as electronic countermeasures do not belong to the scope of this discussion.
Any electronic and electrical equipment may generate human interference. Here, only some common sources of interference that interfere with the measurement environment are mentioned.
(1) radio transmitting equipment: including mobile communication systems, radio, television, radar, navigation and radio relay communication systems. Such as microwave relay, satellite communications. Because of the power of the launch, its base wave signal can produce functional interference; harmonic and distortion emission constitutes a non-functional useless signal interference.
(2) industrial, scientific, medical (ISM) equipment: such as induction heating equipment, high-frequency welding machines, X-ray machines, high-frequency physical therapy equipment. Powerful output power in addition to interference through space radiation, but also through the industrial frequency power grid interference with distant equipment.
(3) power equipment: including servo motors, drills, relays, elevators, and other equipment, pass, break the current generated by the drastic changes and the accompanying sparks become a source of interference: non-linear loads in the power system (eg, arc furnace, etc.), intermittent power supply (UPS) and other homomorphic power conversion equipment generates a large number of harmonic surges into the power grid as a source of interference: fluorescent lamps and other lighting equipment also produces a glow discharge noise interference.
(4) Automobile, internal combustion engine ignition system: automobile ignition system generates broadband interference, from hundreds of kilohertz to hundreds of megahertz interference intensity is almost unchanged.
(5) grid interference: refers to the 50Hz AC power grid by the powerful electromagnetic field and earth leakage current generated by the interference, as well as high-voltage transmission lines, corona and insulation breaks and other poor contact generated by the micro-arc and the surface of the contaminated conductor sparks.
(6) High-speed digital electronic equipment: including computers and related equipment.
The above sources of electromagnetic interference on the generation of the mechanism, there are: discharge noise (lightning, electrostatic discharge, glow discharge, etc.). Contact noise, circuit transition phenomenon, electromagnetic wave reflection phenomenon. Transmission lines in the electromagnetic wave reflection foot high-frequency measurement and digital equipment must be seriously treated as a source of interference.