Logic and evaluation of assuring functional safety from electromagnetic noise

The logic of assuring functional safety from electromagnetic noise is discussed. A configuration example is given of a sensor system hierarchically provided with electromagnetic noise-tolerant capability and electromagnetic noise-resistant capability. Today's international safety standards specify the evaluation of functional safety from the component failure of the system on the basis of the safety assurance process to be performed by the system. Functional safety from electromagnetic noise is evaluated only according to behavior test results. The meaning of the electromagnetic noise requirements specified in the safety standards is clarified in relation to the logic of evaluating functional safety from faults. To achieve high functional safety from electromagnetic noise, it is logically demonstrated that the processing system must have a structure resistant (or fail-safe) with respect to electromagnetic noise. Structures for assuring functional safety from electromagnetic noise in the sensor systems developed by the authors are presented.