Downloaded from https://www.everyspec.com MIL-STD-81OD 19 July 1,983 e SECTION II II-1. ApWEWUS. Any vibration-inducing machinery capable of satisfying the test conditions is acceptable. Specific requirements for test apparatus,are provided in subparagraph c of each subdivision of I-3.2. 11-1..1, ,.~. The acceleration power spectral density of the teat,, control signal shall not deviate from t~e specified requirements by more than t3dB over the entire test frequency range. However, deviations of -6dB in the test control signal may be granted for frequencies greater than 500 Hz due to fixture resonance, teat item resonance, or facility limitations.
The cumulative bandwidth over which this reduction shall be allowed cannot be greater than 5%.of the t&t frequency range (see figure 514.3-37). In no case shall the acceleration power spectral density be more than -6dB below the specified requirements. No deviation shall be grated for frequencies below 500 Hz. When the test cannot be controlled,within+3dB from the specified requirement, at the risk of the tester, the test may oontinue. The risk shall be to asaume no overtesting is occurring, test results are valid, and aPProPria~e corrective action Will be taken in accordance with the nature of the test. Tolerance levels in terms of dB are defined aa: . -. > dB = 10 loglo~l W. where W2 .
measured acceleration power spectral density in g2/Hz units W. = specified level in g2/Hz units. Confirmat+on of these tolerances shall be’made by the providing at least 100 statistical degrees of freedom. use of an analysis system For all !Jrocedures using broadband random vibration with random peaks, sinusoidal peaks, or source dwell, analysis systems shall be less than or equal to 10 Hz in bandwidth up to and including the frequency.,ofthe highest peak in the test spectrum. A digital analysis system is the preferred method for performing a power spectral density control and analysis.
Digital systems used shall have accuracies in excess of standard analog analysis and control systems with the following capabilities: . a. On-line contiguous filter bandwidth as follows: , equalization/analysissystems having a B = 25 Hz, maximum between 20 and 200 Hz B . 50 Hz, maximum between 200 and 1,000 Hz B = 100 Hz, maximum between 1,000 and 2,000 Hz METHOD 514.3 19 Jllly 1983 514.3-69