Automotive Standards: ISO 7637: Road Vehicles -- Electrical Disturbances from Conduction and Coupling

ISO 7637 is an ISO (International Organization for Standardization) automotive standard that applies to the electrical testing of automotive vehicles. 

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ISO 7637: Electrical Disturbances from Conduction and Coupling, and Electrical Transient Conduction Along Supply Lines of Road Vehicles.

There are five (5) sections to date for this standard. The sections are:

1) ISO 7637-1:2015 - Part 1: Definitions and general considerations

Electrical and radio-frequency disturbances occur during normal operation of many items of motor vehicle equipment. They are generated over a wide frequency range and can be distributed to on-board electronic devices and systems by conduction, coupling or radiation.

In recent years, an increasing number of electronic devices for controlling, monitoring and displaying a variety of functions have been introduced into vehicle designs. It is necessary to consider the electrical and electromagnetic environment in which these devices operate and, in particular, the disturbances generated in the vehicle electrical system itself. Such disturbances can cause degradation (temporary malfunction or even permanent damage) of the electronic equipment. Moreover, "worst-case" situations are usually those resulting from disturbances generated inside the vehicle by, for example, ignition systems, generator and alternator systems, electric motors and actuators.

Annex A specifies a general method for function performance status classification (FPSC). Typical severity levels are included in an annex of each of the other parts of ISO 7637.

While narrowband signals generated on or outside the vehicle (by broadcasting and radio-transmitters) can also affect the performance of electronic devices, and recognizing that protection from such potential disturbances has to be considered as part of total system certification, these matters are nevertheless outside the scope of ISO 7637 and are not covered by it.

ISO 11451 and ISO 11452 specify test methods for immunity to radiated disturbances for vehicles and for components, respectively. ISO 10605 specifies test methods for immunity to electrostatic discharge (ESD) for vehicle and for components.

This section defines the basic terms relating to electrical disturbances from conduction and coupling used in the other parts of ISO 7637. It also gives general information on the whole ISO 7637 series.

2) ISO 7637-2:2011 - Part 2: Electrical transient conduction along supply lines only

This section specifies test methods and procedures to ensure the compatibility to conducted electrical transients of equipment installed on passenger cars and commercial vehicles fitted with 12 V or 24 V electrical systems. It describes bench tests for both the injection and measurement of transients. It is applicable to all types of road vehicles independent of the propulsion system (e.g. spark ignition or diesel engine, electric motor) Function performance status classification for immunity to transients is also provided.

3) ISO 7637-3:2016 - Part 3: Electrical transient transmission by capacitive and inductive coupling via lines other than supply lines

The fast transient pulse test uses bursts composed of a number of fast transient pulses, which are coupled into lines (I/O lines in particular) of electronic equipment. The fast rise time, the repetition rate and the low energy of the fast transient bursts are significant to the test. The slow transient pulse test applies a number of single pulses, as used for conducted transient pulse test, to the DUT.

This section establishes a bench top test for the evaluation of the immunity of devices under test (DUTs) to transient transmission by coupling via lines other than supply lines. The test transient pulses simulate both fast and slow transient disturbances, such as those caused by the switching of inductive loads and relay contact bounce.

Three test methods are described in ISO 7637-3:2007:

A) the capacitive coupling clamp (CCC) method;
B) the direct capacitive coupling (DCC) method; and
C) the inductive coupling clamp (ICC) method.

Only one test method need be selected for slow transients and only one method need be selected for fast transients.

ISO 7637-3:2007 applies to road vehicles fitted with nominal 12 V, 24 V or 42 V electrical systems.

For transient immunity, Annex B provides recommended test severity levels in line with the functional performance status classification (FPSC) principle described in ISO 7637-1.

4) ISO 7637-4:2016 - Part 4: Electrical transient conduction along shielded high voltage supply lines only

5) ISO 7637-5:2016 - Part 5: Enhanced definitions and verification methods for harmonization of pulse generators

Pulses in vehicles are generated by different switching events of electrical loads connected to the supply system and coupled via the wiring harness to other components or wires. For test purpose, these pulse phenomena are simulated by pulse generators and coupled via coupling structures to the wiring of a device under test. The test pulses are not real pulses but representatives for the wide range of pulse shapes, amplitudes, source resistances and pulse energy observed in vehicles. The definition of the test pulses and the coupling structures are described in ISO 7637-1, ISO 7637-2 and ISO 7637-3. Based on the standard definition, test equipment has been developed and is commercially available.

The experience with existing test equipment shows some difficulties in terms of result reproducibility for the same DUT dependent on the used generator, which is caused by different realization of test generators coupling and decoupling networks. The intention of this document is to describe the background for these variances and to define methods for harmonization of different generator behavior.

This section proposes extended definitions for pulse generators and verification methods necessary for harmonization of different generators used for pulse testing in accordance to ISO 7637‑2 to ensure the comparability and reproducibility of test results independent on generator types. It presents generator verification results based on current definitions of ISO 7637‑2, which shows significant differences depending on the used generator type and explains the technical background of the variances.

"ISO 7637-1:2015," ISO, n.d. Web, October 2015
"ISO 7637-2:2011," ISO, n.d. Web, October 2013
"ISO 7637-3:2016," ISO, n.d. Web, July 2016
"ISO 7637-4:2016," ISO, n.d. Web,
"ISO 7637-5:2016," ISO, n.d. Web, November 2016
"ISO 7637 – EM Test," EM Test, n.d. Web, October 29, 2013