Cold testing (Test A) - operation, transport and storage at low temperature.
The method specifies cold 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 low temperature.
The specimen may be powered or unpowered, packaged (simulating transport and storage) or unpackaged (simulating use). The standard does not cover the effects of temperature changes; these are addressed by other parts of the 60068 series.
The test demonstrates that the product withstands a specified low temperature under steady-state conditions for a defined time and remains functional after testing. It covers only steady-state cold. Thermal shock, icing and condensation effects are outside its scope.
An “IEC 60068-2-1” entry without temperature and exposure time says nothing about severity; severity is selected by the product standard or specification.
The standard distinguishes three variants: Ab for non-heat-dissipating specimens, Ad for heat-dissipating specimens powered after temperature stabilization, and Ae for heat-dissipating specimens powered throughout the test.
A specimen is considered heat-dissipating when the hottest point on its surface in free air after stabilization is more than 5 K above ambient temperature. The chamber operates with low or high air velocity; the boundary is a reduction in temperature at significant points of more than 5 K caused by circulation, and for high velocity the standard restores a nomogram procedure for correcting the conditioning temperature (Ad and Ae tests).
Sequence: initial measurements, pre-conditioning, lowering temperature at a limited rate, exposure for time t1 after thermal stability is reached, return to normal temperature, recovery and final measurements.
In the 2007 edition, chamber temperature change did not exceed 1 K/min (average over up to 5 min), and low air velocity was up to 0.5 m/s. Severity (temperature TA and exposure time t1) comes from the standard’s tables of preferred values, with the specific pair selected by the product specification.
The datasheet must state the test temperature (°C), exposure time (h) and test variant (Ab, Ad or Ae), and for powered equipment whether it operated during the test. “IEC 60068-2-1” alone without these data is only informative.
