Re: Inductance meter?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 > Is it possible get useful measure of  self- and mutual inductance in
 > Henries or microhenries by (a) ramping a current with predetermined slew
 > rate through a coil, or (b) by  breaking a fixed current flowing through
 > the inductor  in a fixed time, by virtue of the voltage induced in the
 > current-carrying inductor, or a separate coil inductively coupled to it?

This seems too complicated. It's easier to apply a fixed voltage step
V and observe the inclination di/dt of the resulting current ramp.
V1=L1*di1/dt. For mutual inductances, observe the secondary voltage
(no load) and the primary current: V2=M*di1/dt.
Coil resistances add errors, not very easy to remove.

 > Could the ping tester be amended to allow such measurents?

Yes. It you add a small resistor to measure the primary current with an
oscilloscope, you can use the method described above. It's also possible
to add capacitors in series with the coils. The resonance frequencies
and
the known capacitors allow the computation of the inductances. With both
sides tuned to the same frequency, the beats in the voltage waveform
at the primary side allow the computation of the coupling coefficient.

Antonio Carlos M. de Queiroz