A method and apparatus for detecting a change in an internal configuration of a platform. The medical device has a layer overlying the exterior surface of the medical device. The inflator has an igniter that directly ignites the main gas generant in the inflator. The thickness of the low-k CMP protective layer can be adjusted to accommodate larger variations in the CMP process without significantly impacting the effective dielectric constant of the structure. The signal generator is designed for the emission of at least two signal beams covering in given relationship to each other an area and the signal receiver is designed for the time-resolved reception of the signal beams in such a manner that the generator-receiver distance can be determined from the time signature of the signal beam reception.