Re: gEDA-user: Looking for a project

[al davis <ad136@xxxxxxxxxxxxxxxx>]

On Tuesday 03 April 2007 02:41, Ramakrishnan Muthukrishnan 
wrote:
> On 4/3/07, al davis <ad136@xxxxxxxxxxxxxxxx> wrote:
> > If you look at the designs of older ones, you will see that
> > they did it with 2 or 3 tubes.   The basic design can be
> > updated to use today's components, with significantly
> > improved performance.
>
> Wes Hayward's book EMRFD has some designs.
>
> > Another one that could be useful is a "Q-meter".  It is
> > used for measuring inductors and capacitors by resonance.
>
> I started designing a small LC meter using an AVR
> microcontroller. Stalled because of lack of time. Have to
> revisit.

I mean a good old-fashioned one that is completely analog.  
There is an oscillator, then an amplifier driving the "circuit 
under test" in parallel with a variable capacitor.  You adjust 
the variable capacitor to peak or dip, I forgot which.  The 
good old resonance formula tells you the inductance.  The meter 
tells you the Q.  I still have one.  Based on the kind of tubes 
in it  I think it was made about 1940.


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