GB/T 2421-2020 in English

《GB/T 2421-2020环境试验 概述和指南》由TC8（全国电工电子产品环境条件与环境试验标准化技术委员会）归口，主管部门为国家标准化管理委员会。

GB/T 2421-2020 Environmental testing - General and guidance

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

Note: Tests covered by this standard may, in themselves, consist of a series of operations in order to determine the effect of such a test, or series of tests, on a specimen.

3.1
test
complete series of operations implied by its title, normally comprising the following operations, if required:

a) pre-conditioning;

b) initial examination and measurements;

c) testing;

d) recovery;

e) final examination and measurements

Note 1: Intermediate measurements may be required during testing and/or recovery.

Note 2: When the temperature and humidity for testing of a specimen for measurement are the same as those prescribed for pre-conditioning, the pre-conditioning and testing may be merged, and the pre-conditioning may be said to take the place of testing for measurement.

3.2
pre-conditioning
treatment of a specimen being testing with the object of removing, or partly counteracting, the effects of its previous history

Note 1: Where pre-conditioning is called for, it is the first process in the test procedure.

Note 2: Pre-conditioning may be affected by subjecting the specimen to climatic, electrical, or any other conditions required by the relevant specification in order that the properties of the specimen may be stabilized before measurement and test.

3.3
testing
exposure of a specimen to environmental conditions in order to determine the effect of such conditions on the specimen

3.4
recovery
treatment of a specimen, after testing, in order that the properties of the specimen may be stabilized before final measurement

3.5
specimen
specimen of product designated to be tested in accordance with the procedures of the IEC 60068 series

Note: The term "specimen" includes any auxiliary parts or systems that are integral functional features of the specimen, for example systems for cooling and heating.

3.6
heat-dissipating specimen
specimen with the hottest point on its surface, measured in free air conditions and under the air pressure as specified in 4.3, more than 5K above the ambient temperature of the surrounding atmosphere after thermal stability has been reached

 
Note: Measurements required to prove that a specimen can be classified as either heat-dissipating or non-heat-dissipating can be made under standard atmospheric conditions for measurement and tests if care has been taken that no outside influence (for example draughts or sunlight) affects the measurements. In the case of large or complicated specimens, it may be necessary to make measurements at several points.

3.7
air conditions
conditions within an infinite space where the movement of the air is affected only by the heat-dissipating specimen itself

3.8
relevant specification
set of requirements to be satisfied by a specimen, and the method(s) necessary to determine whether the requirements given are satisfied

3.9
ambient temperature
temperature of the air (further defined in 3.9.1 and 3.9.2)

Note: In applying these definitions, guidance should be sought from IEC 60068-3-1.

3.9.1
non-heat-dissipating specimens ambient temperature
temperature of the air surrounding the non-heat-dissipating specimen

3.9.2
heat-dissipating specimens ambient temperature
temperature of the air in free air conditions at such a distance from the heat-dissipating specimen that the effect of the dissipation is negligible

Note: In practice, the ambient temperature is taken as the average of temperatures measured at a number of points in a horizontal plane situated between 0mm and 50mm below the specimen, at half the distance between the specimen and the wall of the chamber, or at 1m distance from the specimen, whichever is less. Suitable precautions shall be taken to avoid heat radiation affecting these measurements.

3.10
surface temperature
case temperature
temperature measured at one or more specified points on the surface of the specimen

 
3.11
thermal stability
state when the temperatures of all parts of the specimen are within 3K, or as otherwise prescribed by the relevant specification, of their final temperature

Note 1: For non-heat-dissipating specimens, the final temperature will be the mean (in time) temperature of the chamber in which the specimen is placed. For heat-dissipating specimens, it is necessary to make repeated measurements to determine the interval of time for the temperature to change 3K, or as otherwise prescribed by the relevant specification. Thermal stability has been reached when the ratio between two consecutive time intervals exceeds 1.7.

Note 2: Where the thermal time constant of the specimen is short compared with the duration of the exposure to a given temperature, no measurement is needed. Where the thermal time constant of the specimen is of the same order as the duration of the exposure, checks shall be made for non-heat-dissipating specimens to ascertain that:

a) non-heat-dissipating specimens are within the required limit of the mean (in time) ambient temperature;

b) for heat-dissipating specimens the ratio between two consecutive time intervals exceeds 1.7 when repeated measurements are made to determine the interval of time required for the temperature to change by 3K, or as otherwise prescribed by the relevant specification.

IEC 60068-3-1 gives background information on the testing of specimens with and without heat-dissipation.

Note 3: In practice, it may not be possible to make direct measurements of the internal temperature of the specimen. A check may then be made by measuring some other parameter which is temperature-dependent and for which the temperature dependence is known.

3.12
chamber
enclosure or space in some part of which the specified conditions can be achieved

3.13
working space
part of the chamber in which the specified conditions can be maintained within the specified tolerances

3.14
combined test
tests during which a specimen is subjected simultaneously to two or more environmental influences

Foreword II
Introduction IV
1 Scope
2 Normative references
3 Terms and definitions
4 Standard atmospheric conditions
5 Use of test methods
6 Climatic sequence
7 Component climatic category
8 Application of tests
9 Significance of the numerical value of a quantity
Annex A (Normative) Component climatic category
Annex B (Informative) General guidance on environmental testing
Annex C (Informative) Environmental test tailoring
Annex NA (Informative) Series of relevant national standards
Bibliography
Figure C.1 Environmental test tailoring process
Table 1 Standard atmospheres for referee measurements and tests
Table 2 Standard atmospheres for measurements and tests
Table 3 Standard conditions for assisted drying
Table B.1 Choice of tests as a function of objectives and applications
Table B.2 General sequence of tests
Table B.3 Principal effects of single environmental parameters
Table C.1 Test tailoring process with information flow and the corresponding activities