Direct answer
Both govern automotive EMC but point in opposite directions. CISPR 25 covers emissions — the limits on interference a product radiates and conducts outwards. ISO 11452 covers immunity — the test methods for applying interference from outside. Certification needs both: one tests that you do not disturb others, the other that you survive when others disturb you.
Comparison in one table
| Dimension | CISPR 25 | ISO 11452 |
|---|---|---|
| What it governs | Emissions | Immunity |
| Energy direction | Product → outside | Outside → product |
| What the result is | Measured level vs limit | Applied level vs functional status |
| Typical items | Radiated emission, conducted emission | Radiated immunity (ALSE, BCI, stripline, direct injection) |
| In plain terms | Your noise must not be too loud | Your noise tolerance must be high enough |
What CISPR 25 measures
CISPR 25 specifies the electromagnetic emission limits and measurement methods for automotive electronic components in the vehicle environment, in two directions:
- Radiated emission: electromagnetic waves the product sends out through space, measured as field strength at the antenna
- Conducted emission: interference travelling out along supply or signal lines, measured with a current probe or by the voltage method
Limits are graded into classes, with a smaller class number meaning a stricter limit; which class applies is specified by the OEM. The same product can pass under one class and fail under another.
What ISO 11452 measures
ISO 11452 specifies immunity test methods: an electromagnetic field or injected current of a defined strength is applied from outside and the product's functional degradation is observed. Common methods include:
- ALSE method: a field is applied by an antenna inside an anechoic chamber, covering a wide frequency range
- BCI (bulk current injection): interference is injected onto the harness through a current injection probe
- Stripline method: a stripline produces a relatively uniform field, suitable for small components
- Direct injection: injection straight into a port, used for specific verification
Judgement is not "did it break" but the functional status class (A / B / C / D) specified by the customer.
Why you cannot do only one side
Passing emissions only shows the product does not disturb others; passing immunity shows it can withstand being disturbed. OEM acceptance generally requires both sides, and doing half means a supplementary test.
From failure experience, immunity problems surface more readily in the real vehicle — the electromagnetic environment is more complex than in the laboratory, and the harness routing and grounding do not exactly match the test conditions.
Correspondence with the Chinese standards
- CISPR 25 → GB 18655 (identical adoption)
- ISO 11452 → the GB/T 33014 series
- Transient conducted immunity → the ISO 7637 series, corresponding to the GB/T 21437 series
The three sets cover different directions: emissions, radiated immunity and transient conducted immunity. Do not bring ISO 7637 into a comparison with CISPR 25 — that is a question on another axis.
Where we stand
TMC LAB holds both CMA and CNAS accreditation. Automotive EMC covers the emission items of CISPR 25 / GB 18655 and the immunity items of ISO 11452 / GB/T 33014. We can issue a test list for the class your customer specifies.
Related pages for this question
Last updated Technical criteria follow the current standards and the agreed scope; please confirm the specific project with the lab.
