Downloaded from https://www.everyspec.com MIL-STD-81OD 19 Jllly1983 d. ~. Because of the variety of permissible lamps and chamber designs, it is particularlY important that the chamber be cali- brated’to assure that the proper levels of radiant infrared energy are impacting the teat area when heat,alone is of concern and that the proper intensity and spectral distribution of solar radiation are impacting the test area when actinic effects are of concern. Over the area covered by the test item, the radiation intensity must be within ~lOf . As the lamps age, their spectral output changee.
To insure that solar radiation chamber; meet estab- lished specifications, a check on spectraldistribution, intehsity, and uni- formity shall be performed at intervals not exceeding 500 hours of operation to insure that the facilities continue to meet established specifications. This value is based on the manufacturer1s guarantee for minimum bulb life. 11-1.3 ~ (See General Requirements, 4.5.4.) (1) ~. The test rationale ia based on the total cumulative effect of the solar environment. Any ~ndertest interruption should be followed by restabilization at the specified conditions and continuation of the test from the point of the interruption. (2) >rocedure 1.
If an interruption occurs after 18 hours 20 minutes of the last cycle of procedure 1, the test shall be considered complete. (At least 92 percent of the test would have been completed, and the probability of a failure is low during the remaining reduced levels of temperature and,solar radiation.) 9 b. ~e. Any overtest conditions must be followed by a thorough examination and checkout of the teat item to verify the effect of the overtest. Since any failure following continuation of testing will be difficult to defend as unrelated to the overtest, a new test item should be used. II-2.1 ~. Before initiating any testing, determine from the test plan: a. Uhich test procedures are required’. b.
The diurnal cycle to be used, c. Other variables, such as number of cycles, etc. . 11-2 . 2 ~ . All items require a pretest standard ambient checkout to provide baseline data. Conduct the checkout as followe: Step 1. Install the teet item in the chamber and stabilize it at standard ambient conditions (General Requirements, 4.4a) and in a manner that will simulate service usage, unleaa the storage configuration ia specified. Position the test item in accordance with the following: M3THOD 505.2 505.2-13 19 July 1983