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 substitute'.
I know I can weigh it, provided it's not on a spool or motor winding already.
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 either.
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.
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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 diameter.
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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)
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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.
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.
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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 world.
To do the same you'll need a chart to convert from cross-sectional area to AWG. Google will find you one.
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.
I read in sci.electronics.design that Reg Edwards wrote (in ) about 'wire size question', on Thu,
7 Apr 2005:
Malt vinegar gauge - brown and sharp. (;-)
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From: "Henry Kolesnik" on Thurs,Apr 7 2005 10:15 pm
lineal
and
and
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...
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.
IIRC there's something called Formvar that will self-strip upon application of a tinned iron.
There's also the chemical stripping agents.
...Jim Thompson
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I read in sci.electronics.design that Ian Stirling wrote (in ) about 'wire size question', on Fri, 8 Apr 2005:
I'd like to see you do that with 30 gauge wire. For an encore, you could do it with 46 gauge. (;-)
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