Nick Steele Reverse-Engineered Digital Calipers Into an Open-Source $32 Linear Encoder, Gapped With Two Layers of Kapton Tape
Nick Steele's open capacitive linear encoder reads to about 40µm against a Mitutoyo indicator, costs roughly $32 to build, and sets its 0.1mm air gap with Kapton tape. KiCad files, STM32 firmware and test data are public.