IEC 60068-2-14 pdf download

IEC 60068-2-14 pdf download Environmental testing – Part 2-14: Tests – Test N: Change of temperature
1 Scope
This part of IEC 60068 provides a test to determine the ability of components, equipment or other articles to withstand rapid changes of ambient temperature. The exposure timesadequate to accomplish this will depend upon the nature of the specimen.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60068 (all parts), Environmental testing
IEC 60068-2-1 , Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-1 7, Environmental testing – Part 2-17: Tests – Test Q: Sealing
IEC Guide 1 04, The preparation of safety publications and the use of basic safety publications and group safety publications
3 Field conditions of changing temperature
It is common in electronic equipment and components that changes of temperature occur. Parts inside equipment undergo slower changes of temperature than those on an external surface when the equipment is not switched on. Rapid changes of temperature may be expected
– when equipment is transported from warm indoor environments into cold open air conditions or vice versa,
– when equipment is suddenly cooled by rainfall or immersion in cold water,
– in externally mounted airborne equipment,
– under certain conditions of transportation and storage. Components will undergo stresses due to changing temperature when high temperature gradients build up in an equipment after being switched on, e.g. in the neighbourhood of high wattage resistors, radiation can cause rise of surface temperature in neighbouring components while other portions are still cool.
Artificially cooled components may be subjected to rapid temperature changes when the cooling system is switched on. Rapid changes of temperature in components may also be induced during manufacturing processes of equipment. Both the number and amplitude of temperature changes and the time interval between them are important.
4 General
4.1 Design of change of temperature tests Tests Na, Nb and Nc comprise alternate periods at a high and at a low temperature with well- defined transfers from one temperature to the other. The conditioning run from laboratory ambient to the first conditioning temperature, then to the second conditioning temperature, then back to laboratory ambient is considered one test cycle.
4.2 Test parameters
Test parameters comprise the following:
– laboratory ambient;
– high temperature;
– low temperature;
– duration of exposure;
– transfer time or rate of change;
– number of test cycles.
The high and low temperatures are understood to be ambient temperatures which will be reached by most specimens with a certain time-lag.