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wire size question

Discussion in 'Electronic Components' started by Albert, Apr 7, 2005.

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  1. Albert

    Albert Guest

    Does anyone know how to measure or determine the wire size. I have
    tons of motors, solenoids, and similar items. I need some #24 wire and
    some #30 for a coil, but have to be sure regarding the wire diameter
    as it's a critical ap and the author of the article says 'don't

    I know I can weigh it, provided it's not on a spool or motor winding

    My local electrical shop has a wire gauge, but it stops at 18 gauge.

    A microscope might work, but ones that have calibrated distance
    measuring on the eyepiece are expensive.

    Perhaps a milliohm meter might be able to measure the difference in
    resistance of a foot of it or so, but that's hardly a standard item

    Any suggestions?


  2. Ian Stirling

    Ian Stirling Guest

    Vernier caliper may also work.
    Either under $30US.
  3. Dave Platt

    Dave Platt Guest

    Does anyone know how to measure or determine the wire size. I have
    A cautionary note - if it's that critical, then re-using wire which
    has alread been wound might not be the best idea. You'd be starting
    with wire which had already been bent/flexed, and if you aren't
    careful this might put some kinks or irregularities in the winding of
    your new coil which might affect its impedance or Q.
    You might be able to do it with a vernier caliper.

    24 gauge has a diameter of .511 mm or .0020"

    30 gauge has a diameter of .255 mm or .001"

    Every 3 gauge numbers corresponds to a 2:1 ratio in wire area (amount
    of copper). Every 6 gauge numbers corresponds to a 2:1 ratio in wire
  4. Gary S.

    Gary S. Guest

    Two quick options:

    Many kinds of wire have information printed on the insulation.

    There are many tables which give the diameter, so machinists verniers
    or a mike would do.

    Or you could collect a set of samples of known wires and compare. Note
    that solid and stranded are a little bit different.

    Recycling solid wire from other coils might leave kinks or weak areas
    where it was bent before. Insulation integrity matters, too.
    Happy trails,
    Gary (net.yogi.bear)
  5. Get a nice piece of smooth round rod and tightly wind a little over a lineal
    inch of wire closely spaced as possible. Count the turns in one inch and
    divide the number of turns into one inch and you'll have a very good
    measurement without any cost.

    Hank WD5JFR
  6. Albert

    Albert Guest

    Thanks to my friend who emailed me the answer.

    Around 5 dollars on ebay, wire gauge measuring gauge 1 to gauge 36.

    Had no idea they made them that small.

    Thanks to (you know who you are) and to all who made suggestions.

  7. Pooh Bear

    Pooh Bear Guest

    If I need to check, I use a vernier caliper to determine the diameter of
    the strands ( 2*r )and then calculate the total cross-sectional area as (
    pi*r^2 ) * number of strands.

    This gives a result in mm^2. Which is the standard measure in most of the

    To do the same you'll need a chart to convert from cross-sectional area to
    AWG. Google will find you one.

  8. Ooops, you're low by a factor of 10:1 in the inch calculations. Just
    as well, since a caliper is hardly repeatable to 1 thou, let alone
    measuring a diameter of that size with any accuracy.

    Best regards,
    Spehro Pefhany
  9. Dave Platt

    Dave Platt Guest

    Ooops, you're low by a factor of 10:1 in the inch calculations. Just
    as well, since a caliper is hardly repeatable to 1 thou, let alone
    measuring a diameter of that size with any accuracy.[/QUOTE]

    Yup, I added a zero in there. 24 gauge is 20 mils (.02"), 30 gauge is
    half that.

    Works out to 50 or 100 turns per inch, close-wound, and the suggestion
    to use that method was probably the best and cheapest I've heard.
  10. Reg Edwards

    Reg Edwards Guest

    Which gauge are you using?

    British Standard wire gauge (SWG) ?
    American wire gauge (AWG) ?
    Birmingham wire gauge (BWG) ?

    They're all different.
  11. Bill Janssen

    Bill Janssen Guest

    And don't forget to remove any insulation before measuring the wire.

    Bill K7NOM
  12. Ross Herbert

    Ross Herbert Guest

    Correct Bill. However DO NOT scrape the insulation from the wire since
    this can alter the physical diameter of the wire. It is best to dip a
    portion of the wire in fast acting paint stripper and wipe the
    softened insulation off with a rag.

    Ross H
  13. Use a micrometer or a vernier slide gauge to measure the diameter.
    Assuming that your wire is enamelled, 24 AWG is 0.022 inch (maybe +/-
    0.002) diameter and 30 AWG is 0.011 inch diameter.
  14. I read in that Reg Edwards
    Malt vinegar gauge - brown and sharp. (;-)
  15. Ian Stirling

    Ian Stirling Guest

    Blowtorch to heat to dull red heat, and then wipe insulation off.
  16. Ross Herbert

    Ross Herbert Guest

    Sure is another option if nothing else. However, methinks it would
    take just as much time to get a blowtorch out and running as it does
    to open a can of paint stripper. It only takes 30 secs to soften the
    insulation, and believe me, the result from the blowtorch is nowhere
    as neat as the paint stripper.
  17. Ross Herbert

    Ross Herbert Guest

    B&S is AWG.

  18. Genome

    Genome Guest

    Well.... ignoring other things..... perhaps you'd like to explain why it's
    so critical or give a link to the article.

  19. I read in that Ian Stirling
    I'd like to see you do that with 30 gauge wire. For an encore, you could
    do it with 46 gauge. (;-)
  20. Guest

    From: "Henry Kolesnik" on Thurs,Apr 7 2005 10:15 pm
    A non-destructive measurement is best. Along about
    1946 my middle school (we called it "junior high" back
    then) electric shop instructor demonstrated how to use
    a mechanical caliper and how NOT to squeeze too hard in
    doing so. Soft-drawn copper common to wire is fairly
    easy to squash when using a caliper. Using one requires
    a VERY light touch on the wire, just enough to be able
    to pull it slightly through the caliper jaws. Even so,
    pulling on soft-drawn copper wire is going to distort it
    slightly so the measurement is going to be on the small
    side. Snipping off ten or twenty short lengths, then
    measuring the total width and dividing by the number of
    lengths will be a bit better in accuracy.

    A pocket optical comparator is handy for this and other
    uses, especially when trying to get a measurement on
    something already mounted with epoxy, varnish, etc. as
    in windings of electric motors. While the "100-foot
    resistance test" is a practical idea with a roll of
    wire, it is hard to do when the wire comes from a
    motor or transformer giving its all to the project.

    As a practical matter, the wire size in small (such as
    HF range) coils won't matter much on either the
    inductance or Q tolerance. For example, Dropping from
    30 AWG to 32 AWG isn't going to be a disaster in
    cylindrical ("solenoidal") or toroidal forms. The
    change in inductance will be aligned-out on trimming
    in the circuit itself. Q is going to change much more
    depending on the material of the coil former and the
    presence of nearby conductive objects such as shields.

    If a Twenty is too much for a pound or so of new wire
    stock, then nobody can afford a Q Meter or inductance
    meter to do an accurate measurement. Get with some
    friends/acquaintences and share the cost of new stock.

    Just some practical thoughts after doing a bit of
    winding in my time...

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