RE: Pythagorean Idea for Inductance Meter?

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tobias.hofer-at-bluewin.ch>


 >-- Original-Nachricht --
 >Date: Sun, 10 Nov 2002 12:58:30 -0700
 >From: "Tesla list" <tesla-at-pupman-dot-com>
 >To: tesla-at-pupman-dot-com
 >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?
 >
 >
hello

this method is possible, in my opinion it's to complicated. a conventional
inductance meter works in an other way.
the voltage on a inductor depends on the change of current and time.
it's given by the equation UL = L*dI/dt. it means the current follows the
voltage.the inductance is also the oposite to a capacitor.
i you put a dc voltage to an inductor the current rise in 'e-function'.
in practice a known voltage is applied to the L an the the current via.
time
is meassured. so you can  calcultage easily the inductance.