ISO 7637 is an automotive EMC test standard that outlines testing requirements for simulating electrical transients in road vehicles with 12V or 24 V electrical systems. ATEC carries EMC test equipment designed to meet the test specifications of ISO 7637-2, the latest version of the standard. Read on for more information about ISO 7637, applicable test pulses, and recommended ISO 7637 test equipment.
What is ISO 7637?
ISO 7637 defines test parameters for the EMC testing of road vehicles, specifically the simulation of electrical disturbances, or transients, in vehicle power supply lines. The standard, which covers both susceptibility and emissions testing, defines proper waveforms for test pulses and lists necessary electrical components. ISO 7637 also offers performance classifications for test pulses based on their frequency, strength, and burst cycle; ratings vary between pulses, and for the 12V or 24V electrical systems of commercial vehicles.
Automotive manufacturers across the world rely on ISO 7637 to ensure the electromagnetic compatibility of their electrical systems; it is a common requirement for vehicle component development. Discovering a vulnerability to transients early on in automotive design is essential, as failures during formal EMC testing waste companies’ time and money.
ISO 7637 is designed to protect car electronics that are vulnerable to surges from automotive power supplies. Since the advent of EMC testing, manufacturers have developed their own EMC standards in response to the myriad of electrical disturbances to which road vehicles fall victim. ISO, the International Organization for Standardization, developed ISO 7637 as a universal standard that covers as many varieties of automotive transients as possible.
ISO 7637 Subsections
ISO 7637 is composed of five parts:
- ISO 7637-1
- Definitions and general considerations
- ISO 7637-2
- Electrical transient conduction along supply lines only
- ISO 7637-3
- Electrical transient transmission by capacitive and inductive coupling via lines other than supply lines
- ISO 7637-4
- Electrical transient conduction along shielded high voltage supply lines only
- ISO 7637-5
- Enhanced definitions and verification methods for harmonization of pulse generators
ISO 7637-2 Test Pulses
ISO 7637-2 specifies the following test pulses for automotive EMC testing:
- ISO 7637-2: Pulse 1
- Pulse 1 is applicable to the EUT if the equipment is connected parallel to an inductive load. This pulse simulates negative transients that occur when a power supply is disconnected from an inductive load.
- Pulse 1 needs to be generated a min. of 500 times.
- ISO 7637-2: Pulse 2a
- Pulse 2a is utilized to simulate a transient that would occur as a result of a spontaneous disconnection of current, which ultimately stems from the wiring harness inductances. This positive voltage spike is often thanks to current build-up in the wiring harnesses; when the equipment ceases to sink current, energy stored in the harnesses triggers the voltage spike.
- Pulse 2a should also be generated a minimum of 500 times.
- ISO 7637-2: Pulse 2b
- Pulse 2b is used to replicate transients that happen when the ignition is off and DC motors are serving as generators, like when a heater keeps running after the driver turns off the car.
- Pulse 2b is repeated 10 times at minimum.
- ISO 7637-2: Pulse 3a & 3b
- Pulses 3a and 3b are generated to replicate transients that happen due to switching processes, like electrical arcing over relays and switches. The capacitance and the inductance of the wiring harness directly affects the pulse’s electrical characteristics.
- Pulses 3a and 3b should be applied continuously for 1 hour.
ISO 7637 Test Equipment
ATEC recommends the following products for testing according to ISO-7637. Typically, testers will need a transient immunity generator, an emissions test system, a LISN, a battery test system, and more. Need help choosing a comprehensive EMC test system? Call 800-404-2832
or submit a rental quote and an ATEC associate will guide you to the right equipment.