Specifying Physical Limitations: A Case Study of an Oscilloscope

This paper extends the work on developing specifications of electronic instruments of Norman Delisle and David Garlan from Tektronix. As with their original, the specification abstracts away from user interface and implementation issues, and the specification is simplified by considering the behaviour of the oscilloscope over all time, rather than incrementally. We present a specification of a simple, single-channel, single-trigger oscilloscope in two phases: 1. the specification of an ideal oscilloscope --- this makes use of concepts from real analysis to capture the ideal behaviour of an oscilloscope, and 2. the relaxation of the conditions of the specification to an extent that allows implementation within the bounds of physical limitations. The main contribution of our paper is the treatment of physical limitations in the second phase; these turn an unimplementable ideal oscilloscope into a realistic oscilloscope that can be physically implemented. As with the work of Delisle and ..