SAE J1113/28 notes that vehicle electrical/electronic systems may be affected when immersed in an electromagnetic field generated by sources such as radio and TV broadcast stations, radar and communication sites, mobile transmitters, cellular phones, and so forth. Other SAE standards for evaluating EMC include:

• Performance Levels and Methods of Measurement of Electromagnetic Compatibility of Vehicles, Boats (up to 15 m), and Machines (16.6 Hz to 18 GHz), J551/1 and
• Function Performance Status Classification for EMC Immunity Testing, J1812

The SAE is certainly not the only organization involved in standards for automotive applications. The Automotive Electronics Council (AEC) Component Technical Committee also has several documents that detail requirements for ESD, stress and IC latch-up testing. Also, the Institute of Electrical and Electronic Engineers (IEEE) EMC Society has ten technical committees that deal with EMC from management, measurement and environment aspects to electromagnetic interference control and high power electromagnetics.

As part of the board of directors of the IEEE EMC Society, Kimball Williams says the EMC Society makes a very strong effort in its standards committees to provide liaison and communication efforts with other technical organizations that are dealing with electronics and potentially with EMC in electronics. Kimball is the EMC Society’s liaison for SAE and CISPR/A (International Electrotechnical Commission) from the radio interference side.  [See sidebar: Relating National and International Standards.]

Component and Vehicle Level Testing for EMI/EMC

With all of the standards for EMC, getting started can be daunting task. Jastech EMC Consulting, LLC brings a systems engineering approach to EMC. James Muccioli, EMC consultant at Jastech, says,“The first thing you’re going to do is bound your system.”  Once the limits of how far to test are established, the requirements need to be researched.

The systems engineering approach used by Jastech starts with bounding the system to determine the level of testing required. Source: Jastech EMC Consulting, LLC.

”Each car company typically has vehicle level tests that they run. Then there are system level requirements, module level requirements, component and even down to the IC level requirements for EMC,” says Muccioli. EMC is like any other feature explains Muccioli. If you expect good EMC performance, it needs to be taken into account up front in the design process. “Once you understand what your environment is from both immunity and an emission standpoint, then you can start designing your electronics module or your system around that,” he says. 

Muccioli cautions that some types of logic react differently than other types.  In addition, EMC considerations impact components, software, and layout including wiring and packaging and more. EMC validation at the earliest prototype level may avoid problems later.

When all the systems are assembled into the vehicle, EMI/EMC chambers for testing complete vehicles are quite common.  In fact, General Motors has four large anechoic chambers that are a hundred feet on a side. “They can put an 18-wheel vehicle in there and run it on the rolls,” says Williams.

Analysis Tools

Identifying potential EMC problems should be part of the system analysis performed on the design. One frequently used technique is Failure Mode and Effects Analysis (FMEA). The FMEA is such a common automotive tool that there is even an SAE spec for it. SAE has J1739 for Potential Failure Mode and Effects Analysis in Design (Design FMEA), Potential Failure Mode and Effects Analysis in Manufacturing and Assembly Processes (Process FMEA) and even one for non-automotive applications, ARP5580. Automotive suppliers also use the Automotive Industry Action Group (AIAG) FMEA methodologies.

General Motors vehicle-level EMC chamber easily accommodates one of its larger light vehicles with the capability to engage all vehicle systems including all four wheels. Photo courtesy of Jacobs Engineering.  Test Chamber provided by ETS-Lindgren. www.ets-lindgren.com Source: www.emcsociety.org/EMC2008/EMC2008/TechnicalTours.html

A design FMEA analyzes the impact on the system design to determine how potential failure modes affect the system operation.  This analysis is used to prioritize failure modes based on the risk to system operation, safety and/or customer satisfaction. Both software and hardware are considered in the FMEA that can be performed at any level from the component up to the complete system.

“Nowadays you link that [the FMEA] with design of experiments,” explains Bogden. With an initial FMEA, design of experiments helps organize the testing approach including analyzing a particular area for focus. Other well-known and frequently used analysis tools include Taguchi Method, Design for Six Sigma, Reliability Block Diagrams (RBDs) and Fault Tree Analysis (FTA).

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