Re: Pythagorean Idea for Inductance Meter?

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

Original poster: "Crow Leader by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

You can get a huge number of op amps for $50 as well.

I like the idea of analog math. Everybody is lazy these days and just throws
microcontrollers at everything. I doubt anybody could even build a
mechanical adding machine anymore.


KEN
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, November 10, 2002 6:22 PM
Subject: Re: Pythagorean Idea for Inductance Meter?


 > Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
 >
 > This is kind of how some of the older impedance bridges work.  These days,
 > they digitize everything and use a microprocessor to do the math.  You can
 > get a more than powerful enough micro and display to do this sort of thing
 > for around $50...(it doesn't need to be a ball of fire, speed wise..)
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Sunday, November 10, 2002 11:58 AM
 > Subject: Pythagorean Idea for Inductance Meter?
 >
 >
 >  > Original poster: "Jolyon Vater Cox by way of Terry Fritz
 > <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >  >
 >  >
 >  > For the purpose of measuring the inductance of the windings used in TCs
,
 >  > is it possible (and economical) to design a meter for true inductance
 > using
 >  > Pythagorean principles -based on fact that the AC voltage across a coil
 >  > with no resistance is proportional to the AC current alone?
 >  >
 >  > I envisage using two opamps (wired as squarers) to register voltages
 > across
 >  > L the test inductor and a reference resistor R connected in series
across
 >  > an AC supply
 >  >
 >  > the squares of the two voltages would be subtracted in a difference amp
 >  >
 >  > then square-rooted (by an opamp with a squarer in the feedback loop) to
 >  > give the voltage component due to inductance alone; the latter would be
 >  > displayed on a meter as a measure of the inductance.
 >  >
 >  > Is this method as simple as it sounds or more complicated in practice?
 > Does
 >  > anyone have a schematic for such a circuit?
 >  >
 >  >
 >
 >
 >