Have a look at the Shimadzu site (and similar) for their non-contact
extensometers

Bye.

        -----Original Message-----
        From:   Jinx [SMTP:joecolquitt@CLEAR.NET.NZ]
        Sent:   Wednesday, 10 May 2000 19:38
        To:     PICLIST@MITVMA.MIT.EDU
        Subject:        [OT] Vernier scales

        Talk of printing encoders reminded me of a project at the back of
        the cupboard.

        I got part-way through an optical ruler, which I wanted to have very
        fine resolution. Originally I tried a printed transparent scale but
        couldn't get the lines small or sharp enough.

        Is it possible that I could use a sliding Vernier scale with the
fixed
        scale, and if so can anyone suggest how to achieve the best results
        with a micro ? I'm thinking of a ruler with a pointer at the '0'
position
        and a pointer on the movable section, the distance between the two
        displayed on an LCD. Perhaps I'm re-inventing the wheel -- is there
        already a product around like this ?

        Now that laser diodes are so cheap do you think it feasible to
measure
        short (500mm) distances on a ruler using light interference
techniques,
        and again, if so, what detection method could be used for a micro ?