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Originally Posted by RPS69
Agreed, aligning it could be tricky. The linear is also truth.
It also have a great advantage. You could place it at the bottom of a long stick, and still have precision, while pots moving in a very short arc are far less reliable.
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Distance from the magnet is not how to get linear angle from a Hall sensor! The Hall reads only on 1 axis. You align the axis dead center over the magnet center between N and S poles. When the magnet turns, the strength of the field along the Hall axis changes. That is what you measure.
Try the other way, you will need more than 1 magnet and the fields will affect each other, merge, and you won't get good results.
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To achieve that kind of precision with optics, you will need some demultiplying system.
Now... so much precision got a draw back, filtering is MANDATORY!
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Optical... a lot can be done using laser-printed transparency graphics you can get printed at most any office store.
Have you ever looked at how ball mice track motion? Or used a vernier?
I have read that working with the dimensions of a Young's double-slit can yield a high number of interference bands. Perhaps diffraction from a single slit can also be used.
Really, the number of ways is a study in itself.