The purpose of pre-compliance testing is to find problems, not to issue certificates. Its value lies in exposing problems at a stage where cost has not yet multiplied.
Why do it during development
- The later a problem surfaces, the more expensive it is to fix. Changing a PCB at EVT stage is only re-routing traces; discovering it after mass production means board revision, scrap inventory and re-certification — an order-of-magnitude difference.
- EMC problems usually originate in PCB layout and mechanical design, where the cost of change multiplies later on.
- Problems found at the screening stage still leave room to prepare a corrective plan and a verification schedule.
How to run pre-compliance
- Come with specific questions: telling the engineer which problems you are worried about in this revision is far more efficient than a general request to run an EMC test.
- Bring engineering prototypes: pre-compliance does not need production parts, but the structural differences from the production part must be stated.
- Measure in sync: ask for the spectrum to be watched during the test, so key frequency points can be tied to design parameters.
- Get corrective advice: ask for a direction based on measured data, not just a report that the limit was exceeded.
- Verify by re-test: after corrective work, run a targeted re-test to confirm the improvement.
Recommended schedule
- EVT stage: EMC pre-compliance plus pre-compliance on key environmental items, to verify design margin.
- DVT stage: full testing to the customer requirement, covering all specified items.
- Before mass production: issue formal reports per regulatory and OEM requirements.
Service notes
Our laboratory holds both CMA and CNAS accreditation, covers about 10,000 m2 and runs more than 500 sets of equipment. All testing is carried out in our own laboratories — nothing is subcontracted. Plant visits and on-site witnessed testing are welcome.
Scheduling follows the actual project pipeline. You can state your preferred lead time when you submit samples; we will confirm a feasible plan against current capacity and keep you updated at each milestone.
Pre-compliance versus formal testing
Both run on the same equipment; the difference is purpose and depth. Pre-compliance can sweep only the key bands and apply a single severity condition, with the data used to locate problems; formal testing runs every item in the standard, with the data used to issue a report. Sample state differs too — pre-compliance accepts engineering prototypes and records the differences from production parts, while formal testing has explicit requirements on sample state. Mixing the two leaves the data serving neither end: it cannot locate the problem, and it cannot support a report.
Typical pre-compliance combination
- EMC pre-scan: locate the key radiated and conducted frequency points, iterating with corrective work.
- Temperature cycling pre-compliance: verify design margin at the common levels of GB/T 28046.4 / ISO 16750-4.
- Power adaptability: work through overvoltage, voltage drop and start-up behaviour item by item.
Add or remove items according to product form: lighting products add dust and water protection, display products add optical parameters.
How to use pre-compliance data
Pre-compliance reports are not for external submission. Their value lies in three places: determining the corrective direction (which trace or which interface a frequency point corresponds to), assessing design margin (how many dB below the limit, how many cycles remaining), and leaving a baseline for corrective verification at the PV stage. After corrective work, a targeted re-test compared against the same source data makes the improvement obvious.
