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Hall rotary encoder tempco--wisdom?

Discussion in 'Electronic Design' started by Phil Hobbs, Jan 8, 2014.

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  1. There are a couple of options for sensing shaft rotation. As someone else
    already mentioned the optical encoder I will confine my response to
    suggesting that you could use a Synchro/Resolver to monitor the shaft. These
    can be quite accurate over fairly wide temperature regimes. The decoding of
    resolver signals (Sin/Cos) is not that difficult and there are chips from
    Analog Devices that will provide a digital output from the signals. You can
    even get rate of rotation informtion from them.

    Paul E. Bennett IEng MIET.....<email://>
    Forth based HIDECS Consultancy.............<>
    Mob: +44 (0)7811-639972
    Tel: +44 (0)1235-510979
    Going Forth Safely ..... EBA.
  2. Guest

    John already solved it--the encoder frequency isn't guaranteed stable,
    and the software was measuring pulse width instead of duty cycle.

    Cool gadgets.

    James Arthur
  3. The most negative way is usually the intended one. When you're writing
    a spec you have to make your product look better than the competition,
    and they're doing it too.
    That's great! I hate things that "almost work".

    By the way, getting a real environmental chamber might not be a bad
    idea now that you've got the room for it (and 3-phase power?). You can
    discover a lot of interesting stuff by logging gigs of data and
    running over the whole temperature range- even on supposedly mature

    I was recently debugging someone else's design and discovered an
    interesting temperature-dependent instability at would never have been
    seen otherwise. It went bonkers repeatably at two distinct
    temperatures (with the temp moving in either direction). Can't discuss
    the cause or cure, but that was a strange one.

    Best regards,
    Spehro Pefhany
  4. Hi Tim,
    Yeah I was going to plot it up, log (R) vs 1/T.. but I've got a new 'puter at work and I've yet to get my old copy of Origin installed... But maybe later today/
    Well I don't know exactly what it is. Pieces that I inhereted from elsewhere.
    There's a nice article "Low Temperature Transformation in Ferrites", L. Bickford, Rev. mod. Physics, January 1953 pg75. Where he looks at magnetite and see's a nice phase transition at ~120 K. (change in R, magnetization and peak in specific heat.) Kinda showy.
    OK I don't know about the semi conductor nature. I looked at some other beads and found that the conduction wasn't a bulk effect. But looked more like percolation... resistance was not proportinal to the length.

    George H.
  5. Den torsdag den 9. januar 2014 18.01.01 UTC+1 skrev Tim Wescott:
    with more than one magnet that could quickly get complicated, permanent
    magnets are ~2000ppm/C

  6. Ambient.
  7. Phil Hobbs

    Phil Hobbs Guest

    In this case, it was just measuring the right thing. Which is good,
    because the clinical trial starts in a week. ;)


    Phil Hobbs

    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
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