May 2014 – HOW2POWER recently published VPT’s article entitled “Using Ruggedized EMI Filters to Pass the CS101 Requirement of MIL-STD-461DF.” In this article, the CS101 requirements are examined. Its implications for the design of the power system – the combination of input EMI filter plus power converter – are discussed. The CS101 test method is presented, including a number of testing precautions that designers should observe.