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ISO 7637: “Road vehicles — Electrical disturbances from conduction and coupling”
ISO 7637 is the automotive standard that sets out test methods for evaluating conducted immunity at the module level.
ISO 7637 defines test methods for determining how modules react to transient disturbances (conducted immunity).. ISO 7637-1 sets out general principles and can be purchased and downloaded from the ISO. It has four separate parts, with parts 2, 3, and 4 outlining specific test methods. A summary of what is in each part is included below.
For a given electronics module that draws typical 12V power, testing to both ISO 7637-2 and -3 will likely be needed. For units that interface with shielded high voltage power lines in an electric vehicle, ISO 7637-4 will apply. There are a lot of transients associated with operating a car/bus/truck–power surges on startup, transients from large inductive loads (motors) switching on and off, transient interruptions as connections are jostled loose by the bouncing of the car over roads for multiple years, etc. Testing for conducted immunity can be a significant portion of your overall EMC testing schedule.
ISO 7637 shares with ISO 11451 the structure of evaluating unit performance based on a functional performance status classification system, which is useful even outside the automotive industry.
ISO 11451: “Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated electromagnetic energy”
ISO 11451 is a collection of test methods addressing vehicle level immunity to electric fields.
ISO 11451 is a collection of documents that describe automotive test methods for testing at the vehicle level to show immunity to various levels of electromagnetic environment. You can purchase 11451-1 here, and the same site has the other parts available as well. The parts are all revised on their own schedules, with Part 1 (current version published in 2015) expected to have a new revision published in 2024.
ISO 11451 is applicable to any kind of passenger car or commercial vehicle, whether traditional internal combustion engine or electric. Its test methods cover the frequency range 10 kHz - 18 GHz, but it is more often applied within a narrower range, such as 1 MHz - 2 GHz. Table 1 lists the different test methods available.
*LUF = lowest usable frequency of a particular reverb chamber.
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Remember that the plane wave illumination at each frequency in ISO 11451 testing isn’t a constant continuous wave. Different modulations are applied to different frequency ranges to better capture real world threats.
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ISO 11451 defines a set of functional performance status classifications (seen below). Widely used in the automotive industry, these categories can be helpful in defining the success criteria for immunity/susceptibility testing for many complex systems, either at the platform or module level. When a device under test has many functions, some of them may be more critical than others. For instance, if the infotainment system gets knocked offline, that’s inconvenient for the user, and the manufacturer may want to address the issue if it happens at too low of a field strength, such that it might happen often. On the other hand, if the headlights can get turned off by any of the test exposures, that would be a major safety concern that would have to be addressed. Combining the criticality of different functions with the performance status classifications from ISO 11451 in a test plan can be a good way to predetermine which “failures” or “anomalies” are acceptable and which must be labeled failures and fixed. It’s a more detailed framework than the “must function normally” criteria found within some immunity/susceptibility test plans.
ISO 11452: “Road vehicles — Component test methods for electrical disturbances from narrowband radiated electromagnetic energy”
ISO 11452 is a standard with multiple parts and test methods that covers testing components that will go on vehicles (cars, trucks, etc.) for immunity.
ISO 11452 covers automotive components for immunity testing--with, as we see with several other standards, a whole lot of parts that can be bought separately. You can see which parts cover which test methods in the tables below. You can start by looking at ISO 11452-1 (“General principles and terminology”) which is available for purchase here. The current version is from 2015 and a new revision is expected in the next year or so.
ISO 11452 uses CISPR 16 to govern the measurements equipment used. Annex A of ISO 11452-1 has a very useful normative guide on how to classify the performance of different functions during testing (you would not call a test a failure if an infotainment system spontaneously reset during moderate level testing; the brake system doing the same thing would be considered a critical failure).
You might notice similarities between ISO 11452 and its various parts and those of SAE J1113. That’s not a coincidence--J1113 was essentially the North American version of the same document until they came into agreement.
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If you have the facility available, testing in a reverb chamber (ISO 11452-11) is often the fastest way to test and also the one most likely to find problems. That sounds like a bad thing, but it’s much better to find problems when it’s one component in a chamber instead of troubleshooting an entire vehicle.