Hi Paul,
Yes I did just change it, something a bit different I suppose.

The meter consumes 40mA according to the manual but I guess that I would need to couple it to a scope in case they are charging up a capacitor to give it a wallop of say an amp for 1 ms.

Regards

Rob

Hi Rob,


Wow! That's really saturating.   I quickly counted 42 turns on your MEG.  Might be off a few.  Is that close?  I did this in FEMM using my core material, which requires about 1.7 times less applied field to saturate than your core. A few weeks ago I created a FEMM model for my material.  At 42 turns my core saturates at just 8 mA.  Although it only requires 2 mA reach half saturation.

These cores are awesome! I'm convinced there's enough stray 60 Hz current to saturate these cores just by touching one of the winding wires. Anyhow, even if an induction meter generated say 0.5 mA the core would still be saturated unless you first degauss the core because these cores have high coercivity-- square BH curves.  So first, the L meter would have to degauss the core and then apply the 0.5 mA AC.

You bring up a good point about a possible cap in meter that might generate an initial current surge. Personally I wouldn't spend any time on measuring the cores inductance and Q for now. If for some reason you cannot replicate Naudin's scope shots then it might pay off to build a simple degasser.  I built one out of a 10 turn high precision pot and a 60 Hz AC voltage source. You only need to make sure the initial current, depending how many turns on your core, is enough to fully saturate the core, and the final current is definitely low enough after turning the pot all the way.  The idea is apply 60 Hz AC current and then slowly decrease the current.  You could do the same with a fancy circuit, but I'm always in a hurry.  Although, given that these cores are ridiculously sensitive it is very difficult to keep these cores degaussed.  As you know, the human body is a big capacitive antenna. Just getting close to the wires generates AC current. And what about radio signals?  There are dozens of radio stations near by. So the wires could pick up these signals.


Regards,
Paul Lowrance

Hi Paul,

Bit off topic, but I have just finished fitting a blue LED illumination disc between the fan switch and the ceiling in the bathroom.
Made it from a GU10 LED lamp (18 blue LEDs) and some 10mm acrylic sheet (shaped using a table router). Had to break all the glass away from the PCB boad using a drill vice, desolder each LED and then shaped the PCB to fit into the back of the switch.
Looks very good (bright blue glow) when you switch on the fan now.

I have to agree with you about the low current saturating the core, from all my FEMM sims it was nearly always around the 10 to 20mA of current at 500 turns for this size of core even for silicon steel.

I am fosusing on building the pulse circuit now and I need to work out the capacitors required to create the overlapping freqencies.
I have log and lin 10K pots, so one of them should provide a linear sweep over the frequency, not sure which so I ordered both.

Regards

Rob

Quote from: kingrsI have to agree with you about the low current saturating the core, from all my FEMM sims it was nearly always around the 10 to 20mA of current at 500 turns for this size of core even for silicon steel.

Supposedly your core has permeability of 600000 as compared to like 5000 to 10000 for SiFe. :-)

Quote from: kingrsI am fosusing on building the pulse circuit now and I need to work out the capacitors required to create the overlapping freqencies.
I have log and lin 10K pots, so one of them should provide a linear sweep over the frequency, not sure which so I ordered both.

You're still replicating the Naudins MEG?  I think the MEGv2.1 is a good start since that seems to be the only Metglas MEG that Naudin shows all the necessary voltage and current scope shots.


Regards,
Paul Lowrance

Hi Paul.

I may try this to build this after the MEG is complete:
http://www.ee.surrey.ac.uk/Workshop/advice/coils/BH_measure.html

Then I can plot the curve for the frequency that JLN came up with.

It would be very interesting to see how the ferrite magnet in place alters the relative permability of the core compared to a vacumm.
In theory the permeability should increase dramatically.

Regards

Rob