Pyrotechnic Shock Testing of Avionics Components

[tomirvine]

NEWS ALERT!

Avionics components in missiles may be subjected to high-amplitude, high-frequency pyrotechnic shock pulses. The components must thus be qualified to these shock levels per MIL-STD-1540D, 810F, etc.

The qualification levels often have so much margin that the tests must be performed in a "near-field" shock environment using plates with detonation cord.

A particular problem arises if "analog anti-aliasing filters" are NOT used in the data acquisition system. In this case, ultra high frequency shock energy may be folded down about the Nyquist frequency, thereby artifically increasing the "apparent" shock level at lower frequencies. This may result in a under-test even though the SRS plots "appear" to meet the specification.

Please include "analog anti-aliasing filters" as a requirement in your shock test specifications.

Recommended sample rates and filter parameters are given in the: IEST Handbook for Dynamic Data Acquistion, IEST-RP-DTE012.2.

Tom Irvine

http://www.vibrationdata.com

 

[jimkinney]

Hi Tom,

I just sat through a SAVIAC class on Mechanical Shock and Data Acquisition a few weeks ago. Excellent class by the way, and we discussed this very topic. Depending on the signal/noise content up to the limit of the accels, the SRS can be off by 10-20 dB or possibly more.

Thanks for the heads up, this is something we all need to be aware of.