These ratings are used to classify the degree of protection provided by an enclosure against external mechanical impacts. Previously, this characteristic was indicated by an additional number added to the end of an IP rating – e.g. IP66(9), however the non-standardised and inconsistent use of this approach led to the development of the IK rating system.
The European Standard EN 62262 specifies the conditions in which enclosures should have their IK ratings tested, detailing types of hammer used, atmosphere, distribution of impact and the radius of the striking element. Although the rating is ultimately dependent upon the impact energy an enclosure can withstand without being compromised, this is measured in joules (J).