Dry heat testing (Test B) - operation at high temperature and low humidity.
The method specifies dry-heat tests for heat-dissipating and non-heat-dissipating specimens. It checks the ability of components, equipment and other products to operate, be transported or stored at high temperature and low humidity.
It applies to powered and unpowered specimens that reach thermal stability during testing, packaged or unpackaged. The standard does not cover the effects of temperature changes.
The test demonstrates that the product withstands a specified elevated temperature under steady-state conditions for a defined time and remains functional after testing. It covers only steady-state dry heat. Effects of humidity, solar radiation and temperature cycling are outside its scope.
Severity is selected by the product standard or specification.
The standard distinguishes three variants: Bb for non-heat-dissipating specimens (powered or unpowered), Bd for heat-dissipating specimens powered after initial thermal stabilization, and Be for heat-dissipating specimens powered throughout the test.
The criterion for a heat-dissipating specimen is a surface temperature more than 5 K above ambient when powered. The chamber operates with low or high air velocity; the criterion is a reduction in specimen temperature of more than 5 K due to circulation, and for high velocity (Bd, Be) the standard restores a nomogram correcting the conditioning temperature.
Sequence: initial measurements, pre-conditioning, raising temperature, exposure after thermal stability is reached, return to normal temperature, recovery and final measurements. Severity (temperature and exposure time) comes from tables of preferred values (Tables 1 and 2), selected by the product specification.
The datasheet must state the test temperature (°C), exposure time (h) and test variant (Bb, Bd or Be), and for powered equipment whether it operated under load during the test. Without these data, the standard reference does not allow two products to be compared.
