Re: gdt

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

Original poster: herwig.roscher-at-gmx.de 


David Speck <dave-at-davidspeckmd-dot-org> wrote:
 > Any simple way to distinguish a powdered iron from a ferrite toroid
 > core?

Dave,

One way to distinguish powdered iron from ferrite is the Curie-
temperature. This is the temperature, the permeability drops to 1.
For RF-ferrite this temperature usually is in the range from 160 deg
C/320 deg F to 200 deg C/392 deg F. Powdered iron changes its
permeability at much higher (e.g. 750 deg C/1382 deg F) temperatures.

So you could wind several turns of teflon (PTFE) insulated wire onto
the core and measure the inductance. Then place it in an oven and
heat it up as high as possible. Remove the core and measure the
inductance again. If it is in the same order, you probably have a
powdered iron core.

Cheers,

Herwig