Re: A cheap L/C meter from frequency measurements

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From: Brad Mitchell (bmitchel@CBA.Kodak.COM)
Date: Fri Jan 28 1994 - 07:18:19 EST


>
> I've heard that it is possible to build a simple inductance and
> capacitance meter by measuring the audio frequency of a LC audio
> oscillator. As I understand it, you use a known L and an
> unknown C ( or an unknown L and a known C ) and then measure the
> audio frequency generated by the oscillator. You then plug all the
> known values into a formula and solve for the unknown.
>
> Now: Has anyone actually built one of these? How did it work? About
> how (in)accurate was yours? Does anyone have a schematic for something
> like this?
>
> Yes, I realize that this sort of thing isn't going to have much accuracy.
> I'm not trying to measure individual component tolerances, but it
> would be nice if I could tell if it was a 47 pf or a 470 pf.
>
> Replies to qrp mailing list or email to dquagliana@attmail.com
>
> Douglas Quagliana
> dquagliana@attmail.com - I speak for myself, not for AT&T
>
>

I just built the Doug Demaw Cap meter and it seems to work very good.
The only problem is is that I need to find a 50 ua meter to complete
the project, but in the mean time, I'll use my digital ua meter to
suffice that I won't use the wrong cap in a project. This meter uses
a 2-3mhz oscillator and a fixed inductance to cause resonance, or max current
flow at 1000pf (The intended max measurment)
 It also has been designed to distribute the capacitance
measurements uniformly over the 50 ua range, or at least somewhat uniformly.
I don't remember what year/month the meter is, but I'll look tonight.
There is also another article that Doug Demaw wrote for an inductance meter
as well, and I have that dog eared as well. I'll try to get that info soon.
73
 -----------------
| ___ ________ | Bradley S. Mitchell WB8YGG
| | / / | | Eastman Kodak Company
| | / / | | KEMD Electronic Products
| |< < K O D A K| | Circuit Board Assembly Dept. 606 Test Engineering
| | \ \ | | 901 Elmgrove Road Rochester, N.Y. 14653-5211
| |__\ \________| | (716) 726-5775, FAX (716) 726-7109
| | INTERNET: bmitchel@kodak.com
 -----------------


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