Automotive electromagnetic compatibility (EMC) testing was initially important for anti-lock braking systems and engine control systems. Today, virtually every automobile operating system includes some component that could produce electromagnetic interference (EMI) or radio frequency interference (RFI), so, these components must be tested to ensure emissions are eliminated or severely mitigated during their operation.
The US is one of the few countries lacking such a requirement, but since US-based automakers commonly export to countries that do have them, suppliers usually proceed as if it is a matter of regulatory necessity. Regardless of exportation plans, the Federal Communications Commission’s Part 15 regulation applies to all electronic products sold in the US, which means that, as a minimum, radio frequency (RF) emissions testing is required for modern vehicles.
Component suppliers are responsible for ensuring their products undergo EMC testing and must do so in accordance with applicable industry and original equipment manufacturer-enforced standards. OEMs will be heavily involved with this process.
There are six major areas of EMC testing:
- Radiated RF emissions (RE): unintended emission of RF energy from electronic devices or systems
- Conducted RF emissions: unintended emission of RF energy travels along conductive paths, such as power lines, signal cables, or other wiring connected to an electronic device or system
- Conducted transient emissions: unintended emission of transient electrical disturbances, such as voltage or current spikes, through conductive paths
- Electrostatic discharge: a sudden flow of electricity occurs between two electrically charged objects due to their differing electrical potentials
- Radiated RF immunity: ability of an electronic device or system to resist and function correctly when exposed to external RF electromagnetic fields. This ensures that the device can operate without performance degradation or malfunction when EMI is present
- Conducted transient immunity: ability of an electronic device or system to withstand and continue to function properly when exposed to transient electrical disturbances from conductive paths.
International standards
The major industry methods governing these tests include the IEC’s CISPR 25 for radiated and conducted RF emissions, ISO 11452-xx for RF immunity, ISO 7637-x for conducted transient immunity and emissions, ISO 10605 for electrostatic discharge and ISO 16750-2 for when electrical loads are involved. Some manufacturers require compliance with their own internal specifications, such as General Motors (GMW3097 and GMW3172), Ford (FMC1278), Fiat Chrysler (FCA CS 00054), and Jaguar/Land Rover (JLR-EMC-CS).
Suppliers are responsible for devising test plans that comply with the requirements of any OEMs with which they plan on doing business, and which sell cars in most major vehicle markets. This requires an understanding of which industry regulatory standards must be met, as well as any specific requirements demanded by individual OEMs. Suppliers must be closely engaged with the EMC testing process to ensure compliance is achieved and can be readily proven on demand.
An automotive EMC test plan
Automotive suppliers are responsible for creating an EMC test plan that complies with OEM requirements before conducting any formal verification or validation via testing operations.
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Tests can be categorised as necessary for design verification or product validation. Any testing outside these parameters is categorised as engineering validation and will not be viewed as an official part of the formal results. The test plan must describe all the components and their normal functions/modes of operation.
Other details that may be incorporated include information about how a component was manufactured, supplier data, environmental conditions for tests, pass/fail criteria, severity levels, and relevant safety procedures.
Testing process steps
On receipt of the OEM’s approval number and once the partner laboratory has been informed, testing can begin. Ideally the testing process will go as described in the test plan to meet all of the standards imposed.
It may be necessary to make adjustments in real time based on unforeseen parameter changes. If the OEM is informed of the intention to adjust the testing process and the manufacturer signs off on the change, it is permissible. For example, a motor for a power window is expected to be run continuously clockwise as part of a test in the plan, but this might not be possible because it is attached to a fixture and cannot travel very far until it stops and must be reset. The OEM must be informed of the issue and told why a change is necessary.
Another example could be that the required orientation of the device during testing prevents the wire harness requirements from being met. In either case, the OEM must be informed of the issue and told why a change is necessary. In many cases an OEM will require continuous updates on test passage or failure, sometimes as immediately as 24 hours or less after each test is conducted.
After being informed of a pass/fail status, there may be a few more days before the car manufacturer demands more detailed reports on the individual tests. Other deadlines will have to be considered throughout the course of the project, including time-to-market.
Choosing a test laboratory
The test laboratory, whether in-house or a third-party facility, must meet ISO/IEC 17025 minimum requirements. This standard enables laboratories to demonstrate that they operate competently and generate valid results, facilitating co-operation between laboratories and other bodies by generating wider acceptance of results. Test reports and certificates can be accepted between countries without the need for further testing, which improves international trade.
If a laboratory can address the entire automotive value chain it streamlines the testing process. A laboratory handling all test needs, from components to full vehicle systems, means there is no need to co-ordinate multiple testing providers. Unified testing improves data reliability and minimises the risk of miscommunication, overlooked tests, or non-compliance. It can also provide insights into how components interact within the vehicle to ensure interoperability and system-level reliability. This all helps to minimise time to market, especially as any compliance or performance issues can be identified and resolved quickly. By bundling services and avoiding test duplication, costs can be minimised.
If working with a third-party laboratory, determine these key factors in advance:
* Equipment: who provides equipment for generating signals during the test process?
* Review: laboratory personnel can review the unfinished plan and make suggestions, but cannot conduct any advanced testing
* Monitoring protocols: what response monitoring protocols will be used (particularly for any tests conducted in an EMC chamber)?
* Information: suppliers should provide software, equipment or any other informational/operational collateral necessary for the laboratory to understand the component and properly conduct testing.
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