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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: Sheila Prather ( )
Organization:Northrop Grumman Corp
Date posted: Fri Oct 26 12:54:29 US/Eastern 2001
Subject: MIL-HDBK-344A - ESS for Electronic Equipment
Mil-hdbk-344A references parametric vs. functional testing? What are the differences in the two?


Subject: ESS Testing
Reply Posted by: B.W.Dudley ( )
Organization: Reliability Analysis Center
Date Posted: Fri Nov 2 11:20:19 US/Eastern 2001
This question on parametric and functional testing in the Environmental Stress Screening (ESS) arena is one that is very interesting as the answer is not obvious and is not in the handbook. After some research in the Reliability Analysis Center library and consulting with experts in this field, I determined that "FUNCTIONAL TESTING" is the ESS testing of a product without power applied to the unit under test during the stress screening. "PARAMETRIC" testing is the condition of applying power to the unit under test during stress screening. As can be seen on page 5-24 of MIL-HDBK-334 Military Standard Environment Stress Screening of Electronic Equipment, the DEFECT detection efficiency is much higher with the parametric testing than with the functional test alone. Of course, parametric testing is far more expensive as higher levels of test and support equipment will be necessary to power and measure the unit under test. The Institute of Environmental Sciences has a guide called "Management and Technical Guidelines for ESS Process, IEST-RP-PR001.1", dated February 2000 that explains power-on and power-off testing. Thank you for calling the Reliability Analysis Center and presenting this very interesting question.

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