Performance Criteria A, B and C: How to Read an Immunity Result

A buyer once waved a test report at me and said "it passed, so we're good." I asked which criterion it passed. They didn't know there was one. That conversation happens more often than it should — and it's the reason this page exists.

The direct answer: immunity results are graded with three letters. A means the product kept working during the test. B means it degraded during the test but recovered after it. C means a temporary loss of function was acceptable if it recovered on its own or by a control operation.

The letter is not a footnote — it is the entire meaning of the pass. Our Model 1338 report documents Criterion A on both ESD and radiated immunity, which is the strongest grade: the charging function kept working through every exposure, not just after it.

Why the Letter Matters More Than the Word "Pass"

"Pass" without a criterion is like "passed the exam" without a grade. A product that resets when zapped and then recovers is compliant at Criterion B for ESD. A product that keeps charging through the spark is compliant at Criterion A. Same word on the certificate — a completely different product experience. Buyers who do not read the letter are buying a summary instead of the story.

The Three Criteria, in Plain Language

Criterion	During the test	After the test	Example in luggage
A	Keeps operating as intended	No degradation	The charging port keeps charging while the RF field is applied
B	Degradation allowed	Must recover, no loss of operating state	The port glitches during a spark but works normally after
C	Temporary loss of function allowed	Must self-recover or recover by controls	The electronics reset but come back when the user re-plugs

The definitions come from Clause 6 of EN IEC 55014-2, and they are the same vocabulary across the whole immunity test family. Learn them once; they apply everywhere.

What Our Report Shows

Test	Required criterion	Documented result
ESD (contact and air)	B	A on the tested points
Radiated immunity (all faces)	A	A on every face, both polarizations

Let's translate that. The ESD standard requires Criterion B — the product may flinch during the spark as long as it recovers. The measurement record shows the 1338 performing to Criterion A, meaning it did not even flinch. The radiated immunity standard requires A, and the report shows A on all twelve exposures.

Factory data, straight from our quality team: when we read a lab's immunity pages, the first thing we look for is the criterion column, not the pass column. A report with "Pass" but no criterion tells us nothing about behavior; a report with "Pass, Criterion A" tells us the product kept working. That is why our own reports carry the letter on every line — and why I'd be embarrassed to hand a buyer anything less.

How Buyers Should Use This Page

Find the criterion column in the immunity results — it should be on every test line.
Match the criterion to the standard's requirement — ESD usually requires B; radiated immunity usually requires A.
Prefer documented A over the minimum — margin in behavior is margin in the field.
Check the monitoring method — the criterion is only meaningful if the report states what function was watched (ours monitors the charging output).

Frequently Asked Questions

What is the difference between Criterion A and B in immunity testing?

A means the product continues to operate as intended during the test; B allows degradation during the test as long as the product recovers and loses no operating state afterward. A is the stronger result.

Which criterion does ESD normally require?

The ESD test under EN IEC 55014-2 requires Criterion B. Our report documents A on the tested points — better than the requirement.

Which criterion does radiated immunity require?

Radiated immunity requires Criterion A — the product must keep operating as intended during the field exposure. Our 1338 passed A on all six faces.

Is a Criterion B pass a real pass?

Yes — B is a legitimate compliance result for tests that require it. The point is to read the letter and know what the product actually did, not to assume every pass is the same.

What does Criterion C allow?

A temporary loss of function, provided it is self-recoverable or restored by a control operation. It is the loosest of the three and is not the grade you want on a charging function.

Why does my factory's report not show criteria?

Some summaries omit the column. Ask for the full immunity pages with the criterion per test line — a report that hides the letter is hiding the behavior.

About This Report

The criterion analysis in this article comes from report No. GTS2025080251E01 for our Model 1338 — ESD at Criterion A against a B requirement, radiated immunity at A across every face and polarization, with the charging output monitored throughout. We share the immunity pages with buyers and help interpret them. Send the report or your questions to clkbusiness@clkluggage.com or WhatsApp +86-18879628221.

About the Author

Written by the CLK Manufacturing Team — 16+ years of custom luggage OEM/ODM experience from our factory in Ji'an, Jiangxi, China. Updated: 2026-08-15.