Application Note

Conducted Transients In Road Vehicles' Supply Lines

Source: AR
By Rodger Gensel and Tom Moyer, AR


Over the last thirty years, the number of electrical/electronic modules used in road vehicles has increased dramatically. The modules are used in many diverse functions, including engine and transmission control, comfort and entertainment functions (radio, air conditioner and heater) and critical safety features (anti-lock brakes and air bag systems). All of the electrical and electronic systems must operate without interfering with each other and without reaction to outside interference signals. The road vehicle is subjected to radiated RF signals as well as onboard radiating signals of its own. In addition, the vehicles electrical system generates transients that are conducted via the power lines to the electrical/electronic modules connected to it. This note explains the transients that are conducted via the vehicle power system and the means by which the electrical/electronic modules are tested for immunity to the conducted transients.


The ability of the road vehicles electrical/electronic system to operate in the vehicular electromagnetic environment is called Electromagnetic Compatibility (EMC). The U.S. government does not regulate the EMC of road vehicles in the sense that it regulates EMC of other equipment such as telephones and medical devices. The major controlling documents for EMC in road vehicles are created by the vehicle manufacturers themselves. In the U.S., these are mainly the big three auto manufacturers, DaimlerChrysler, Ford and General Motors. In addition, specifications outlining EMC performance for road vehicles are written by the Society of Automotive Engineers (SAE) and the International Organization for Standardization (ISO).

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Application Note: Conducted Transients In Road Vehicles' Supply Lines