Apply FMEDA to Guide Self-diagnostic Design for Digital Circuit Board

Abstract

Today Safety Digital Control System (DCS) is widely applied in industrial safety system. Safety DCS is mainly composed of input module, logic control unit, output module, and communication module. Each module is featured with a powerful fault diagnostic capability and it is able to detect the hidden failures. On the other hand, the diagnostic design increases the complexity and the failure of diagnostics may also trigger false alarm, which could lead to production loss. Therefore self-diagnostic measures design is very important for the digital module of safety DCS. Based on the development experience of FirmSys, a safety DCS platform developed by China Techenergy Co., Lit (CTEC), this paper proposes Failure Modes, Effects, and Diagnostic Analysis (FMEDA) technology to evaluate the diagnostic coverage (DC) and false alarm rate (FAR), and guide self-diagnostic design. Through the case study of Digital Output (DO) module, it demonstrates the feasibility of the proposed method.