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Is it safe?
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03/11/2005
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Sometimes things go wrong, it’s unfortunate but it happens. However, in safety critical systems, this philosophical take on Murphy’s Law isn’t acceptable and there’s actually a lot one can do to make sure the worst doesn’t, in fact, happen.
Determining what constitutes ‘safety critical’ would seem like common sense, it’s something that could potentially cause harm or damage. Taking measures to maintain functional safety in operation has historically involved an independent subsystem, used to monitor the primary system and take preventative action in the event of a fault. Advances in microprocessor horsepower means it is now easier to integrate this kind of subsystem in to the main system, instead of independently. As a result it is becoming more ‘mainstream’ – outside of the obvious application areas – to add safety measures. Not least among the reasons for doing so is the commercial advantage it can offer.
Commercial advantage aside, there are some systems where ‘safe’ is essential, not an added bonus. An elevator, for example, must be inherently safe in the event of a failure. With the advent of electromechanical systems, the use of solid state electronic safety features – as opposed to purely mechanical – has increased. To facilitate standardisation in the definition of ‘safe’ and ‘safety related’ systems that are electrotechnical in nature, the IEC produced the international standard IEC61508, which covers all safety related systems which employ electrical, electronic or programmable electronic (electrotechnical for short) devices.
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Author
Philip Ling
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