The treatment of interruption of high and low temperature test chamber is clearly stipulated in GJB 150, which divides the test interruption into three situations, namely, interruption within the tolerance range, interruption under test conditions and interruption under over test conditions. Different situations have different treatment methods.
For interruption within the tolerance range, when the test conditions do not exceed the allowable error range during the interruption, the interruption time should be regarded as part of the total test time; for interruption under test conditions, when the test conditions of the high and low temperature test chamber are lower than the lower limit of the allowable error, the pre-specified test conditions should be reached again from the point below the test conditions, and the test should be resumed until the scheduled test cycle is completed; for over-test samples, if the over-test conditions will not directly affect the interruption of the test conditions, if the test sample fails in the subsequent test, the test result should be considered invalid.
In actual work, we adopt the method of retesting after the test sample is repaired for the test interruption caused by the failure of the test sample; for the test interruption caused by the high and low temperature test chamber test equipment (such as sudden water outage, power outage, equipment failure, etc.), if the interruption time is not very long (within 2 hours), we usually handle it according to the under-test condition interruption specified in GJB 150. If the time is too long, the test must be repeated. The reason for applying the provisions for test interruption treatment in this way is determined by the provisions for temperature stability of the test sample.
The determination of the duration of the test temperature in the high and low temperature test chamber temperature test is often based on the test sample reaching temperature stability at this temperature. Due to the differences in product structure and materials and test equipment capabilities, the time for different products to reach temperature stability at the same temperature is different. When the surface of the test sample is heated (or cooled), it is gradually transferred to the inside of the test sample. Such a heat conduction process is a stable heat conduction process. There is a time lag between the time when the internal temperature of the test sample reaches thermal equilibrium and the time when the surface of the test sample reaches thermal equilibrium. This time lag is the temperature stabilization time. The minimum time required for test samples that cannot measure temperature stability is specified, that is, when the temperature is not in operation and cannot be measured, the minimum temperature stability time is 3 hours, and when the temperature is in operation, the minimum temperature stability time is 2 hours. In actual work, we use 2 hours as the temperature stabilization time. When the test sample reaches temperature stability, if the temperature around the test sample changes suddenly, the test sample in thermal equilibrium will also have a time lag, that is, in a very short time, the temperature inside the test sample will not change too much.
During the high and low temperature humidity test, if there is a sudden water outage, power outage or test equipment failure, we should first close the test chamber door. Because when the high and low temperature humidity test equipment suddenly stops running, as long as the chamber door is closed, the temperature of the test chamber door will not change dramatically. In a very short time, the temperature inside the test sample will not change much.
Then, determine whether this interruption has an impact on the test sample. If it does not affect the test sample and the test equipment can resume normal operation in a short time, we can continue the test according to the handling method of interruption of insufficient test conditions specified in GJB 150, unless the interruption of the test has a certain impact on the test sample.
Post time: Oct-16-2024