The purpose of temperature environmental test is that the good are shipped by various types of carriers and experience a wide range of storage temperatures, depending on the customer environment, hence the need for this kind of testing. Further, certain components and assemblies are sensitive to these temperature extremes and could be weakened due to induced stresses. Therefore, it is important that a logical sequence of testing be followed in order to observe these effects and assure the product’s performance under various temperature conditions and after temperature extremes have been applied.
(Note: This test didn’t include the humidity.)
5.1 Reference Conditions
To start the cycle obtain reference data either in the test chamber or outside using ambient conditions (+25°C±5°C and 50%RH±10%) by completing a performance test.
When changing chamber temperatures, the rate of temperature change (△t) must be controlled. The required △t is 20°C/hour minimum for each temperature transition. After each transition the product must be allowed to thermally stabilize before performance data is recorded, except for the transition from the low operating limit 5.4 to the high operating limit of 5.5. During this temperature transition, the product shall be tested without regard to stabilization of temperature.
The product is considered thermally stabilized when the average of at least four temperatures, as measured on components (transformers, chips, PC boards, etc.) within the product, while it is in the “off” state, is within 2°C of the ambient air temperature. The time is required for the thermal stabilization can be determined from previous thermal profiles on the same product or by making temperature measurements during the test or by calculation based upon the largest thermal mass within the product.
5.2 Low Temperature Operating Test.
All products will be required to perform to specification during the low temperature operating test.
With the product turned on, reduce the chamber temperature from ambient to the product’s specified operating test temperature. Performance testing may be made at any time during the temperature transition. A final performance test shall be made after four hours have elapsed at the low temperature limit.
Note 1. In the case of systems which use an operating system (software) the system must be operating and performing a typical set of operations during all test temperatures excepting when powered down.
Note 2. For products using consumables, tests should include those consumables until the temperature specification for the consumable is reached. Then tests are to be made without the consumable.
5.3 Low Temperature Storage Test
Turn the product off after completing the low temperature test and reduce the chamber temperature to the lower Storage Non-operating Temperature limit. Allow the product to dwell for four hours or until thermal stability is achieved, whichever is longer (no power is applied to the product during this test). then return to the low Operating Test Temperature limit.
5.4 Low Temperature Operating Test.
After reaching the low Operating Test Temperature limit, the product shall be turned on and performance tests made, after the product’s specified warn-up time. Class A1, A2 and B1 products shall function immediately (no warm-up time) and performance shall be within specification within a five-minutes period unless otherwise specified to the customer. For Class B2, C1, and C2 products, if a time is not specified use a 15 minutes warm-up time before evolution is made. This test will provide a cold-start evaluation of the product.
The lowest input voltage specification limit that can be applied for the range selected, shall be used to power the product for warm-up and performance tests. For products that require configuration changes to obtain different ranges, a single range will be used throughout the temperature test cycles (the chamber is not to be opened during this test period).
A final performance test shall be made after four hours have elapsed at the low temperature limit. The product power is to remain on during the next transition to the high temperature limit.
5.5 High Temperature Operating Test.
In accordance with Figure 1, the temperature is now increased to the high Operating Test Temperature limit with the product turned on. Performance tests may be made at any time during the temperature transition. A final performance test shall be made after four hours have elapsed at the high temperature limit.
5.6 High Temperature Storage Test.
Turn the product off after completing the high temperature operating test and increase the chamber temperature to the highest Storage Non-Operating Temperature limit. Allow the product to dwell for four hours or until thermal stability is achieved, whichever is longer.
5.7 High Temperature Heat Run Test.
Return the temperature to the high temperature test limit and allow the product temperature to stabilize. then apply power to the product for a period of 24 hours minimum. Power cycling is required and must be performed a minimum of four times during this test. The highest input voltage specification limit that can be applied shall be used to power the product. This upper voltage limit will be from the same voltage range used for the low temperature operating requirement of Clause 5.4.
Performance measure will be made as a minimum at the beginning and then end of this 24 hours heat run. In the case of systems which are expected to operate continuously 24 hours a day for indefinite periods, the unit under test will be expected to run the operating system executing a set of programs representative of the typical use of the system. This set of programs must run without fault during all test periods.
5.8 Final Temperature Inspection.
Reduce temperature to the ambient reference conditions and check for conformance to specifications after allowing the product to stabilize. In the case of systems, the system shall be allowed to continue to run the program set a minimum of 24 hours after return to ambient conditions. No failures are allowed during any of the performance tests made.
After reference conditions have been verified, remove covers and inspect all assembles thoroughly for any evidence of physical damage or overheating.