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by lynaghk
592 days ago
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Author here. Lots of questions about precision --- in the article I calculated 0.6mm as the standard deviation of 200ms worth of phase measurements (n=124) while the slide wasn't moving. I'd love to hear any advice/ideas re: - approaches for figuring out what's currently limiting the accuracy (i.e., noise sources) - the relative merits of averaging in time vs phase domain - how to improve the analog frontend (See my collaborator Mitko's github repo for the hardware schematics: https://github.com/MitkoDyakov/Calipatron/blob/main/Hardware...) |
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Usually the way you want to set something like this up is with a low pass filter before you sample it and you want to sample at a high enough rate (some multiple of that filter frequency). This is due to the sampling theorem. Maybe I'm missing something.
I would aim for the highest possible sample rate and then post-process the signal (assuming that's computationally reasonable, i.e. you can keep up with real time).
There are general practices/principles for minimizing noise. Having a ground plane. Separating your digital electronics from your analog electronics. Clean power supply. Shielding.
Another thing I'd be concerned about is that this whole thing is a big antenna. Yet another concern is that motion might influence the results (any time you have conductors moving in the presence of fields you get some induced current).
Commercial positioning solutions are usually based on optics and gratings. I wonder if that's a better approach even for a hobbyist. Something like an optical mouse just linearized...