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HMC1052 range and consistency control?

Discussion in 'Electronic Design' started by Johnny Chang, Jul 14, 2008.

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  1. Johnny Chang

    Johnny Chang Guest

    I have installed a number of these compasses on identical boards, and
    I've found that not only do their measurements differ, but also even
    the range of values.

    at the same position and direction, they give significantly different
    values for +/-. This is a slight annoyance having over 50 boards to
    go in the firmware and adjust the offsets before calculating the
    direction, but is this a common thing?

    Lastly and more worrying is the difference in ranges that the values
    give when i read from them in all 360 degrees with maybe 16
    increments. For example, one compass may give a maximum value for +
    of say 2 volts and a minimum of 1 volt, with the same for the -.
    Another may give a range for + of 1.5 volts to 1.7 volts, and the -
    may give 1 volt to 2 volts. And another will have .8 volts to 2.5
    volts for + and 1.1 to 1.15 volts for -. Are these common issues?
    they are all implemented on identical boards.
     
  2. Frank Buss

    Frank Buss Guest

    Did you use the flip coils to reset the offsets? How did you measure it?
    They don't output volts, it is a resistor bridge. Maybe your amplifier
    circuit has some offset or different gain? Can you measure the resistors of
    different parts before soldering (and after applying a pulse to the flip
    coils)?
     
  3. CBFalconer

    CBFalconer Guest

    ....

    We obviously have a considerably different idea of the meaning of
    'compass'. To me, this is an item containing a magnet and pivot,
    that self adjusts to point (more or less) at magnetic north.

    So what are you talking about?
     
  4. Johnny Chang

    Johnny Chang Guest

    Er whoops, instead of + and -, i meant bridge1 +/- difference and
    bridge2 +/- difference. We use the same amplification circuit for
    each one, but I can test them and measure them whenever I get back to
    lab. Yeah, we send a pulse to set/reset.
     
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