Reliability Compliance Testing of Electronic Systems Using Parametric and Non Parametric Sequential Test Plans

Abstract

During design & development, reliability of electronic systems is predicted using well-known prediction methods like empirical models and life testing. Empirical models help to quantify reliability during design phase of systems while life testing or accelerated life testing methods are applied once the system is developed. Assessment of system reliability using these methods follows bottom-up approach and as a result, any latent uncertainty at the component/subsystem level gets amplified at the system level. To deal with the limitations of existing methods and to verify that system reliability goals are met, reliability compliance testing is gaining importance. In compliance testing, system reliability is not predicted but it is demonstrated by testing, whether system conforms to the system requirement or not. This method does not require any additional setup or chamber and it is based on the failure data of system components obtained during testing of systems after installation. Hence, it is very cost effective. In this paper, two sequential compliance test plans for control & instrumentation (C&I) system of a Nuclear Power Plant (NPP) are discussed, using parametric and nonparametric analysis. Parametric analysis assumes exponential time-to-failure distribution while nonparametric analysis is based on distribution free sequential rank-sum probability ratio test. A case study of these plans for a NPP C&I is also presented. Finally, a comparison of both the methods is made.