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Project Help and Ideas » Digital vernier alternative

August 21, 2011
by billshaw
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Hello, Has anyone used a proper linear scale rather than an ordinary digital vernier to measure displacement? The linear scales I am talking about are the ones you will find on lathes & mills. They are generally more robust and accurate, but a bit more expensive. The output from these scales is a TTL signal, which if I understand correctly, is 3 x 5V signals as square waves. 2 signals are used to record the displacement and 1 signal is for direction. I was thinking that it might be simpler than the vernier idea because it already uses 5V and not 1.5V and all that is required is to keep a count of the highs / lows to work our the displacement. On the other hand, you have to make sure that the frequency of checking the status of the signal is high enough otherwise you can miss some high/low changes which would mean the displacement is incorrect. I'd just like to know from the experts (not me) if my idea sounds reasonable or if there is something which I am missing before I get started. Thanks, Bill

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