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Wanted: L/C Meter project

Discussion in 'Electronic Design' started by Paul Burridge, Oct 23, 2003.

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  1. Hi all,

    I'm finding my current meter increasingly useless as it can only
    resolve relatively high values of inductance and capacitance. I really
    need something that can provide accurate read outs of components in
    the order of <5p and <10n. It strikes me this would make an excellent
    home-build project. Does anyone have a design lying about somewhere
    for such a measuring device? Perhaps something from an old QST or one
    of the popular electronics magazines?
    Many thanks.

    p.
     
  2. Joel Kolstad

    Joel Kolstad Guest

    I think it's safe to say a lot of hobbyists have contstructed the Almost All
    Digital Electronics LC meter here: http://www.aade.com/lcmeter.htm . It did
    appear in... umm... Nuts & Volts, maybe? -- some publication -- a small
    handful of years ago.

    ---Joel Kolstad
     
  3. Frank Buss

    Frank Buss Guest

  4. Frank Buss

    Frank Buss Guest

    Yes, but I think the difficult part is the analog part, programming the
    microcontroller is easy, so you don't need it.

    But the relay for calibrating looks not very good. Is it possible to
    substitute it with a chip, perhaps a 4066 quad switch? And perhaps the
    other switches of the 4066 could be used to automaticly switch between L
    and C mode. Then you simply test a component and the LC meter determines,
    if it is a capacitor or a coil.

    With some more analog switches it could be enhanced to an LCR meter and
    with even more switches and microcontroller support you can integrate a
    diode tester and a transistor tester, which can automaticly detect NPN or
    PNP, and the pin assigment (I always forget the pin assigments, so this
    would be a nice feature).
     
  5. Tim Shoppa

    Tim Shoppa Guest

    In that region parasitics are often as large as the part you want to
    measure.

    You have three choices, IMHO:

    1. Unquestioned answers. These are those digital two-terminal things
    you hook a part to, you select the mode, and it gives you a number.

    Those are fun to play with. Especially when the part you are measuring
    gives readings in both "inductance" and "capacitance" mode :)

    2. Unanswered questions. Some grid dip meters seem to fall into this
    category. At least these get you started in thinking out of the
    "this part can be characterized with a single number" zone.

    3. A full-blown network analyzer.

    Chances are that all three alternatives can be avoided with a little
    thought and effort.

    Tim.
     
  6. Thanks, Tim. I'm inclining towards option 3 at present. F*** it; it's
    only money.
     
  7. James

    James Guest

    Paul wrote:
    "Simple Digital Inductance Meter With 0.1nH Resolution," Williams, Rodger,
    RF Design, Oct. 1987 pp50-55.

    (a 3-linear IC design. Classy)

    James

    P.S. I believe the AADE design first appeared as a project in Radio Electronics
    magazine, but, that aside, I don't think it has the resolving power you
    request.. -j


    et.net: delete it. (incoming e-mail subject to brutal filtering)
     
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