An alternative to consider is simple, cheap and usually rock solid: dual edge sensors. The smallest wrinkle will tuck in one or both edges. This is easy for the sensors to see as a ‘width’ change as the resolution of many of the sensors are on the order of a hair’s thickness (0.005”, 125 microns). The only limitations is that the incoming material would have to have slit edges and that the incoming width variation is not large to begin with. Anyone see a product development and marketing opportunity? If you can’t get that satisfaction from the component suppliers, it would still be easy enough to Macgyver together by any self-respecting instrumentation tech.
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