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5th May 2018, 9:54 pm | #21 |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
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Re: Precision inductance tester
Yes, if it has an iron core.
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5th May 2018, 9:58 pm | #22 |
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Re: Precision inductance tester
If it's a single-layer evenly spaced inductor you can get a reasonable value (about 1%) with nothing more than a tape-measure or rule, using Nagaoka's formula. But you may need to use linear extrapolation (depending on the values given in the table you use) for the figures in your formula.
Wheeler's formula is slightly less accurate but still workable for practical purposes. If the value you get is on the edge, you need a different inductor anyway. Unless you're not designing a rigidly-fixed one, of course.
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Regds, Russell W. B. G4YLI. |
5th May 2018, 10:33 pm | #23 | |
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Re: Precision inductance tester
Quote:
And to get there, I calibrated the tester with commercial small axial inductors in the sub 10uH->1mH and found them to be rather scattered around their marked tolerances. When you talk of a tape measure, I imagine rather larger inductors as in tank coils of high-powered commercial transmitters. yes?
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5th May 2018, 10:57 pm | #24 | |
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Re: Precision inductance tester
Quote:
I've used the 'three voltage' Cosine Rule method many times but never above 10kHz. I have a Peak Atlas LCR bridge of my own and it's a pretty useful device and compares well to a HP4192A or Tinsley bridge.
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6th May 2018, 1:27 am | #25 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
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Re: Precision inductance tester
Either that, or he is simply remembering the rules: Stick to Webers, Teslas and express all distances, however short, in metres; and that way, at least you won't make the maths any harder than necessary
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
6th May 2018, 9:47 am | #26 | |
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Re: Precision inductance tester
Quote:
As for other formulaic things I get involved with, I rolled my own spreadsheets to take the onerousness out of such things. It's fun to do and educational from the perspective of actually understanding how the maths applies to the problem as well as the mechanics of spreadsheets themselves, but it is vitally essential to check each step on the way. No doubt those whizz-kids au-fait with low-level programming could come up with something flashier, but spreadsheets work fine for me. A bit like apprentices and tradesmen making their own tools.
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6th May 2018, 12:24 pm | #27 | |
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Re: Precision inductance tester
Quote:
I work in metric units only now. I don't find it at all difficult to convert between millimetres and metres or the other way round.
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6th May 2018, 2:02 pm | #28 |
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Join Date: Jun 2016
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Re: Precision inductance tester
Random slightly on topic thing... For the excel users out there, if you use this cell format it'll display in engineering notation:
##0.00E+0 Very handy |
6th May 2018, 3:06 pm | #29 |
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Re: Precision inductance tester
That’s great! Neat tip, thanks !
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Al |