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Originally Posted by sciguy125
The thing is, encoders only tell you where the system is supposed to be, not where it is. A limit switch (or the like) will tell you when the system is at its limit and should stop. If you only have an encoder you know that you're supposed to be somewhere, but if you have a loose cable or chain, you'll actually be somewhere else.
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Thats only if you design it that way. If you wanted a measurement on the extension of the arm you might use a linear encoder while if you wanted a measurement of arm angle you would mount an encoder to the arm. Your measurements would be accurate.
Personally I like a magnet sensors because the lack of actual contact. I especially like the ones that detect ferrous metals rather then other magnets because it leaves you room to be creative with how you position the sensors (like for example we used little metal strips that we could bend to different shapes). I don't exactly using pots for measuring the angle of an arm because of already said inaccuracy but for measuring objects with smaller radius it is extremely useful. By the way, have any FIRST teams used linear encoders?