In IEC 60068, most of the test information is contained in a few letters. “Ab” and “Ae” are the same cold test but differ in the way the sample is brought to temperature and the way the function is tested. “Db” and “Cab” are both hot and humid tests, but one has a condensation cycle, the other does not.
This article is a decoding table of test designations, along with the most easily confused symbol pairs when writing test requests or reading reports.
1. How test designations are structured
A test in IEC 60068 is usually written in terms of four components:
- Standard number:IEC 60068-2-x (x is part number).
- Test names in alphabetical order:Test A, Test B, Test F…
- Variant (lowercase):Ab, Ae, Bb, Bd, Na, Nb…
- Severity and duration:specified by the request document.
Important points:Uppercase letters indicate groups of actors, lowercase letters indicate implementation methods. Omitting lowercase letters means losing half of the test’s information.
2. Designation decoder by test group
| Group | Typical symbols | Content |
|---|---|---|
| Temperature | A (Ab, Ae), B (Bb, Bd), N (Na, Nb), Sa | Cold, dry heat, temperature changes, solar radiation |
| Humidity | Cab, Db, Cx, Cy, Z/AD, Z/ABDM | Stable humidity and heat, cycles of humidity and heat, combination cycles, and climate chains |
| Vibration and acceleration | Fc, Fh, Fi, Ff, Fj, Fg, Ga | Sinusoidal, random, mixed, time-history, noise-induced, steady-acceleration vibrations |
| Shock and rough handling | Ea, Ec, Ee, Ei, Eh | Mechanical shock, rough handling, bulk cargo, shock according to response spectrum, hammer |
| Corrosion | Ka, Kb, Kc, Kd, Ke | Salt mist, cyclic salt mist, SO₂, H₂S, mixed gases |
| Dust, water, biology | L, R/S/T/U, J | Dust and sand, water, mold |
| Welding and components | Ta, Tb, Td, Te/Tc, Tf, U | Weldability, solder heat resistance, solderability measurement, pin durability |
| Other | M, XA, Xb, Xc, Xw1 | Low pressure, solvents, label abrasion, liquid contamination, tin residue |
3. The designations most often confused
| Pairs are easy to confuse | Core difference | Effects when used incorrectly |
|---|---|---|
| Ab and Ae | How to bring the sample to temperature and when to test function | The results are not comparable to customer requirements |
| Bb and Bd | Same as above, in hot, dry afternoon | Failure to detect errors that only appear when the sample is at high temperature |
| Na and Nb | Two ways to change temperature (speed and number of cycles on request) | Incorrect assessment of the thermal shock resistance of welds and materials |
| Cab and DB | Stable (no condensation) vs. cyclic (with condensation) | Ignore condensation failure mechanisms — a common cause of insulation leaks |
| Test N and heat shock according to other standards | Philosophy for choosing the level and speed of heat transfer | The conclusion is too optimistic or too pessimistic about weld durability |
| Ka and Kb | Continuous salt mist versus cyclic salt mist | Corrosion levels vary significantly, results are not equivalent |
| Fc and Fh | Sinusoidal vibration versus random vibration | Cannot reproduce actual vibration conditions (usually random) |
| Test K and Test C | Chemical corrosion versus hot moisture | Choosing the wrong agent does not answer the question that needs to be answered |
| Test U and Test Xw1 | Mechanical strength of the leg compared to the tin whisker phenomenon | Ignore the risk of electric shock due to tin whiskers growing in the assembly |
4. Combined designations in the standard
Some parts of the standard use compound symbols to designate test series, for example Test Z/AD (combined heat-humidity cycle) or Test Z/ABDM (climate series). With these tests, the order and timing of each phase is part of the test definition, not chosen by the tester.
Additionally, some tests were withdrawn or replaced during the standard review process. When reading old documents and encountering symbols that are no longer in the current version, it is necessary to determine the corresponding replacement test before planning the test.
5. How to write designations in documents and reports
| Incomplete notation | Complete notation |
|---|---|
| Test according to IEC 60068 | Cold test according to IEC 60068-2-1, Ab test, level… time… |
| Try hot humidity | Cyclic hot humidity test according to IEC 60068-2-30 (Test Db), level… number of cycles… |
| Try vibrating | Wideband random vibration test according to IEC 60068-2-64 (Test Fh), level… time… |
| Try salt mist | Cyclic salt mist test according to IEC 60068-2-52 (Test Kb), concentration… number of cycles… |
6. A four-step check of designations before testing
- Compare the original request:Take verbatim customer requirements or product standards, do not use internal summaries.
- Identify parts and symbols:clearly state the part number (e.g. 60068-2-30) and full symbol (Test Db).
- Check severity and duration:Confirm temperature, humidity, number of cycles, exposure time, and power supply status of the sample.
- Agree on achievement criteria:clearly state which test, what threshold, and who validated the results.
These four steps take a little time but help avoid trial and error — one of the most common causes of having to re-do an application.
7. Frequently asked questions
Is writing “Test A” enough?
Not enough. Test A has two variants Ab and Ae with different implementation methods; Variation and severity level should be clearly stated.
Why are there two variants of the cold test?
For different purposes: one variant is more concerned with tolerance to stable conditions, the other is more concerned with behavior when temperature changes and when testing functionality at low temperatures.
Are test designations the same across standard sets?
No. Notation is a convention specific to each set. The symbols of one set should not be used to describe tests of another set.
How do I know a test has been withdrawn?
Compare the current part lists of IEC 60068 and check the replacement notes in the standard. If old documents refer to a withdrawn test, a replacement should be agreed with the customer.
Can several designations be combined in one report?
Yes, and it is common practice when a product goes through a series of tests. It is necessary to clearly state the order, severity and pass criteria for each test.
Does a wrong designation invalidate the result?
Test results may be correct but do not prove the stated claim. In disputes, reports with incorrect symbols are often required to retry.
What if we are not sure about the designation?
Ask the party making the request in writing and ask them to clearly state the standard part number, symbol and severity level. This is a normal technical question, not a weakness of the practitioner.
8. Conclusion
The test designations in IEC 60068 contain technical information, not just reference codes. Reading the correct symbol helps businesses try it right the first time and avoid rework — a cost that is much more expensive than the time spent reading the requirements carefully.
Three things to do: always include the full designation (group + variant) in the requirements document; check the current symbol list before planning; and request the testing laboratory to record the symbol and severity level in the report.
References
- IEC 60068-1 — Environmental testing: General provisions and guidance.
- IEC 60068-2-1, 2-2, 2-14, 2-30, 2-78 — Cold, dry heat, fluctuating temperature, cyclic heat humidity and stable heat humidity.
- IEC 60068-2-6, 2-64, 2-27 — Sinusoidal vibration, random vibration, mechanical shock.
- IEC 60068-2-11, 2-52, 2-42, 2-43, 2-60 — Corrosion tests.
- IEC 60068-5-2 — Terms and definitions.
Related articles
- Cab test: steady heat and humidity according to IEC 60068-2-78
- What is IEC 60068? Structure of the Environmental Testing Standard Set and How to Read Test Codes
- TCVN 7699 and IEC 60068: Vietnam’s Equivalent Standard Set, and When to Use Which
- How to Choose Environmental Tests from the Product’s Real Operating Environment
- How IEC 60068 Differs from MIL-STD-810, ISO 16750, ISTA and IEC 60529
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Disclaimer
This article is an interpretive content compiled by us;not legal advice. Enterprises need to compare relevant documents/standards verbatim before applying them to specific products.
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