Most digital calipers use a capacitive stripe to measure distances, which consist of 0.1" grounded stripes on 0.2" centers. Using the same principle as a Vernie

Most digital calipers use a capacitive stripe to measure distances, which consist of 0.1" grounded stripes on 0.2" centers. Using the same principle as a Vernier caliper, this gets interpolated into resolution down to quite small distances, even in the cheapest harbor freight model. Metric/Imperial scales are done in software. You can use a vinyl cutter to make a pattern in the same dimensions, and stick it on a conductive back, and make an arbitrary sized caliper, subject to the accuracy of the pattern once applied. You could also just machine it with a 0.1" end mill.