Why EMC immunity testing is inadequate for functional safety

Safety-implicated, safety-related, and safety-critical systems are increasingly using electrical, electronic and programmable electronic devices. All such devices can suffer malfunctions or damage due to electromagnetic interference. Safety systems have safety integrity requirements (defined by IEC 61508) - but their EMC aspects are not adequately controlled by either safety or EMC standards. The paper describes the shortcomings in the way that the EMC immunity of such equipment is dealt with, and shows that the normal immunity testing approach is inadequate, on its own, as a means of verifying this aspect of safety integrity.