Re: Inductance measurement

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Original poster: "Dr. Wolfram Steinkamp by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Wolfram-Steinkamp-at-gmx.de>

Hi John

I'm reading your very interesting ideas to measuring inductances.
At last I think in the equation by which an inductance ist defines should be
changed to:

  L (inductance) = flux x N (Number of windings)/ I (value of current)

or is the value of  flux as you write already  multiplied with N?

Stone
-----Ursprüngliche Nachricht-----
Von: "Tesla list" <tesla-at-pupman-dot-com>
An: <tesla-at-pupman-dot-com>
Gesendet: Mittwoch, 2. Juli 2003 19:18
Betreff: RE: Inductance measurement


 > Original poster: "John H. Couture by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
 >
 >
 > Matt -
 >
 > This is a good question and not easily answered. There are many ways to do
 > the job and each meter manufacturer probably uses a different method to
 > measure inductance. I notice the meters are normally rated (+/- 5%) so the
 > accuracy is fairly good whatever method is used. Several years ago when I
 > was working on the homemade Induction meter I show in one of my books I
came
 > to the conclusion the Maxwell bridge circuit would be the best to use. The
 > equation is
 >      L = Ra x Rc x Cb
 > This equation does not involve frequency so the measurement is good at any
 > frequency. The resistance and reactance can be made independent if Cb is
 > made variable. There are many other possibilities shown in EE books.
 >
 > Two coils one with copper and one with nichrome wire would show the same
 > inductance with the Maxwell bridge provided the wire size, turns and
 > geometry of the coils were the same. This would be a good research project
 > for some coiler. I have never heard of any coiler who has ever made this
 > test. I don't believe that connecting different resistors in series with a
 > copper coil will be of any help. I have tried this and found the
inductance
 > doesn't change with the Wavetek DM27XT unless the resistor is many ohms.
 >
 > Inductance is defined as the flux linkages divided by the current causing
 > the flux. This definition is difficult to put into practice when designing
 > an inductance meter.
 >
 > John Couture
 >
 > ----------------------------------------
 >
 >
 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Tuesday, July 01, 2003 7:33 PM
 > To: tesla-at-pupman-dot-com
 > Subject: Inductance measurement
 >
 >
 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > <Mddeming-at-aol-dot-com>
 >
 > Hi All,
 >          Does anyone know how the resistance of a coil affects the
measured
 > inductance using an LC meter (e.g. AADE LC IIB meter, Wavetek, etc.). I am
 > wondering if these meters really measure L, or do they measure delta Z and
 > infer L from it, with the built-in assumption that R<< XL ?
 >          If I have two identical solenoids, one wound with copper wire and
 > the other with, say, Nichrome wire, would they read the same inductance,
or
 > would the larger phase angle fool the meter?
 >
 > Matt D.
 >
 >