In today's automobiles, electronic systems account for 30% to 40% of the total cost. From engine control units to intelligent navigation systems, from airbags to autonomous driving assistance systems, electronic components are spread throughout the entire vehicle like a neural network.. But have you ever wondered why these electronic systems can work stably without interfering with each other when you are using your mobile phone in the car or encountering thunderstorm weather? The answer lies in electromagnetic compatibility (EMC) testing, and the ISO 7637 standard is the "invisible armor" that safeguards automotive electronics safety.
1. Why must automotive electronics pass the EMC test?
The core objective of automotive EMC testing is clear: to ensure that electronic components can both resist interference and not interfere with others in complex electromagnetic environments. It is divided into two main directions:
-EMI (electromagnetic interference test): To prevent components from generating interference waves to "pollute" the surrounding environment, such as avoiding navigation signals that interfere with brake control.
-EMS (electromagnetic susceptibility test): Ensure that components remain "as stable as a rock" under strong interference, such as vehicle radar still working accurately when encountering mobile phone signals.
A car that fails the EMC test is like a time bomb: the wiper may get out of control during the radio broadcast. And the braking signals may be disturbed by the charging of mobile phones... Electromagnetic compatibility is directly related to life safety, so global OEMs all take EMC certification as a mandatory threshold for component access.
2. ISO 7637: The "Touchstone" of Transient Interference in Automotive Electronics.
Among numerous EMC standards, ISO 7637 specifically addresses transient pulse interference specific to vehicles. This type of interference originates from the switching actions of the vehicle's power system and the switching of inductive loads during daily operations, and its high-voltage pulses can break down fragile circuits within microseconds. The latest version of ISO 7637-2:2011 defines 5 types of critical test pulses that simulate sudden crises in real vehicle environments:
1) P1/P2a pulse: A big trouble caused by a small switch
-Scene restoration: the moment when the wiper is turned off or the fuse is blown (such as P1), or when the load suddenly disconnects during ignition (such as P2a).
-Threat: Generate voltage spikes ranging from -660V to +60V, directly impacting the parallel circuit.
-Test requirements: Pulse width of 50 μ s~2ms, internal resistance matching real cable impedance (2 Ω~50 Ω).
2) P3 Pulse: the "lightning storm" around electronic devices
-Scene restoration: relay contact spark (P3a) or electric arc of electric window motor (P3b).
-Threat: An extremely narrow pulse group of 150ns (with an amplitude of up to 300V), like a high-frequency needle piercing through a signal line.
- Equipment solution: A dedicated coupling clamp (with a capacitance of 100pF) is required to inject interference into the wiring harness.
4) P4 Pulse: The "Voltage Cliff" under Heavy Load
-Scene restoration: At the moment of starting the air conditioner or engine, the voltage of the entire vehicle drops sharply.
-Simulation parameters: The 12V system voltage drops from 12V to 6V and then to 2.5V, lasting for 0.5-20 seconds, testing the power supply's voltage stabilization capability.
5) P5a, P5b Pulse: The "Death Surge" of Battery disconnection
-Scene restoration: the battery is accidentally disconnected during driving (such as the pile head is loose).
-Destructive power: The energy of the generator is released nowhere, and the 200V high-voltage surge lasts for 500ms. If there is no protection, the ECU can be directly burned out.
-Safety design: P5b is a standard configuration for new energy vehicles by limiting voltage through clamping diodes.
Why is the 7637 test so critical?
According to statistics, 70% of automotive electronic failures are related to power transient interference, and P1/P5 type pulses can cause control signal disorder, directly triggering safety risks.
3. Entering the Laboratory: A Panoramic Decryption of EMC Testing Equipment
To accurately reproduce the above pulses, a test system consisting of professional instruments is required:
EMCSOSIN automotive pulse simulators
-RV P1P2a (pulse 1, 2a)
-RV P3 (fast transient pulses 3a, 3b)
-RV P5, P5b (load dump pulse 5a, 5b)
Accessories (optional)
-High voltage artificial network: to isolate power supply of the EUT.
-CCC fixture: capacitive coupling clamp, for coupling the fast transient pulses.
-DCC fixture: directive capacitive coupling
-ICC fixture: inductive coupling clamp, for coupling the slow transient pulses
4. From Testing to On-board: How does EMC Safeguard Automotive Safety?
Automotive electronics need to go through a strict process to obtain ISO 7637 certification:
1)Design Verification (DV) : Engineers conduct pre-tests based on standards and optimize circuit protection (such as adding TVS diodes).
2)OEM standard testing: In addition to ISO standards, it also needs to meet enterprise-specific requirements (such as Volkswagen TL 81000, Geely Q/JLY J7110779E).
3)Production Part Approval (PV) : Sample and retest the mass-produced parts to ensure consistency.
Products that pass the test will receive "electromagnetic immunity certification", which will become the cornerstone of safe operation of intelligent vehicles.Today, new energy vehicles have higher requirements for 7637 testing -- The newly added high and low voltage coupling test can prevent the motor's high voltage from entering the 12V system.
When you drive through a heavy rainstorm, the wipers swing steadily; when your phone is charging in the car, the dashboard data remains clear... These 'taken-for-granted' features are backed by the electromagnetic safety barrier established by the ISO 7637 standard. Every time the car window is opened or closed and every time the engine is started, it is a transient test of the electronic system. The significance of EMC testing lies precisely in keeping dangers within the laboratory and ensuring safe driving on every road.
EMCSOSIN RV series complying with old and new ISO 7637-2, ISO 16750-2 standards. It is the best choice for anti-interference testing of various types of automotive electronic products. Please do not hesitate to contact us for more details. Thank you!
