Re: Induction meter

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve Greenfield by way of Terry Fritz <twftesla-at-qwest-dot-net>" <alienrelics-at-yahoo-dot-com>

I'm sending this to a few other groups I'm on, thought
some others might be interested in this project.

Hmm... I'll bet you can. The principle seems to be
that the unknown inductance (Lunk), R3, and IC1-c form
a monostable. It and the clock formed by IC-a and b
make a PWM that has output linearly proportional to
the value of Lunk.

The Range switch just changes the clock by a factor of
10. You could try adding another Range with a 0.1uF
capacitor, that will slow the clock to somewhere
around 500 to 800Hz vs 5 to 8KHz. So I suspect you'll
want to increase the output smoothing capacitor, C2,
or increase R4.

You could try altering the monostable charging
resistor, R3, to a smaller value to decrease the
monostable charging time for larger inductors. But I
don't think IC1-b will put out enough current for
that.

I wouldn't count on this to be too accurate as you are
relying on the rather soft switching point of 1/2Vcc
of the CMOS gates and their rather "soft" output
characteristics. Perhaps a simple redesign using
comparators and a 1/2Vcc reference, or a couple of 555
timer ICs. The 555 has excellent temp and voltage
stability and the TTL version has very sturdy outputs.
If you design this so the clock has to sink rather
than source current for the LR monostable, the CMOS
version could do this.

OK, looks like I've volunteered... ;') This also will
get around the copyright issue, as this PDF is a
scanned article from Radio Electronics or Poptronics
or some other electronics magazine.

Steve Greenfield

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Luc by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <ludev-at-videotron.ca>
> 
> Hi list,
> 
> Can I have your opinion on this, and do you think
> it's possible
> to modified it for an extended reading of bigger
> inductor.
> 
> http://pages.infinit-dot-net/luc2/IndMeterAdapter.pdf
> 
> Cheers,
> 
> Luc Benard
> 
> 
> 


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