Flux gate question

imgur.com

Tim

It's actually the DC resistance of the coils being near the average inductive reactance that causes this asymmetry.

The spikes on the winding common to the two coils occur when the current sweeps through some small interval on either side of zero, in which one of the coils is deeper in saturation than the other. (The region where the B-H curve changes slope.)

At very low frequency, the coil resistance dominates. The curve traced out on an I-U plane is a straight line, crossing the critical current at equal speed in either direction. The spikes are symmetric w.r.t. to peak voltage.

At high frequency, the inductive reactance dominates, the curve on the I-U plane is a (distorted) circle and we're still crossing the critical current at equal speed in either direction, but now the spikes are symmetric around zero voltage.

In the intermediate frequency case, the critical current crossing is unequal in the two directions and one of the spikes sits at a lower voltage than the other, taking more time to cross the critical current, and yielding a lower, longer spike.

So far for intuition. Next is mathematics or simulation...

Jeroen Belleman

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Grin when he said it I thought of Eagle. It may have issues, but it doesn't crash. With all previous pcb software my motto was 'save early and often'. (mind you I still run version 4.15 from years ago.)

George H.

While the German companies will invade your computer. :(

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Same here, version 4.16r2, ten years and counting. Anything after that wasn't really worth the upgrade for me because they didn't include the most predominant missing feature, a hierarchy. But I rather forego a hierachy than tolerate crashes.

Lately there was some talk about a link with LTSpice. No word from their engineers about it so I'll wait. If that ever works really seamlessly or if hierarchy comes I'll send them a check and upgrade.

Take the case of triangle drive (TEK0018.BMP) and note the linear rise to about the peak (large, first spike). Then carefully note the partly exponential current increase as the core saturates. Fast dropoff at saturation, goes to zero. Hysteresis happening here; drive is at slower rate so see slower, lower amplitude pulse. See same thing with reverse polarity drive.

Nothing fancy..

I did a ping on bayimg.com and got 192.121.86.164

A DNS lookup said it is in Stockholm, I think. See

John

I got nothing from dnsstuff before I posted. It told be it wasn't found on any name servers. Maybe it was in transiton from one host to another at the time? That would have caused the problems people were having. I use Open DNS, instead of my ISPs DNS and have very few problems with URLs.

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Thanks Robert, It may be 'nothing fancy' for you, but I'm still trying to get my head around it. I'm 'mostly clueless', when it comes to magnetic materials. So let me try this as a hand wavy explanation, If I just had one inductor, driven by a voltage source then I'd write down the voltage as,

V = d/dt(L*I) +R*I = I*dL/dt + L*dI/dt + R*I

So as I go into saturation dL/dt is negative. The first term looks a bit like a negative resistance. More current is sucked from my voltage source. And conversely coming out of saturation the first term is positive.

I think I'll have to do the one inductor case. There's nothing like data to help guide my thinking. (I happy it's a 'real physics' thing and not a circuit screw up :^)

George H.

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They loaded right up for me.

I recently tried imgbox, it seem to be just fine.

One of my KDE desktops looks like this:

?-)

the

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All 4 just came right up for me. Fast enough that i didn't notice any lag.

?-)

It's possible- worst snow storm in about 5 years yesterday. This is what a 16-lane Toronto expressway looked like about 2:00 pm:

Or, pretty much a normal winter Friday in Buffalo NY.

Best regards, Spehro Pefhany

On a sunny day (Sat, 09 Feb 2013 20:09:12 -0500) it happened Spehro Pefhany wrote in :

mm, its even snowing here and below zero C at night

Obviously global warming.

Sorry. I meant IP Information lookup.

Can be worse:

A friend who lived in Minnesota showed me a similar picture around his house, not too long ago. They had to enter the house via the 2nd floor because that's how high the snow was.

On a sunny day (Sun, 10 Feb 2013 06:40:40 -0800) it happened Joerg wrote in :

Those were real trains, these days the slightest snow on the rails already stopts the high speed train here. Designed by an Italian company, those probably never heard of snow:

Like I said: We no enter the post technology era.

here.

Or the era of sloppy design. Seems that happens more and more, probably also because stuff becomes (to some extent unnecessarily) moer complicated.

What struck me a bit was that the Spoorwegen guy said that they aren't sure yet whether the underside damage is really winter-related. Haven't they diagnosed already what failed?

Thanks for sharing the photo! Especially tying that deadly winter to others' experiences.

My aunt used to live in Minneapolis and one time sent us a picture [circa 50's] showing 9 feet of snow on top her roof. She was lucky the roof didn't join the floor under all that weight, but then again, the houses used to be built for the 'unexpected'.

I had tried every useful tool there and got nothing. Including anything on the domain registration.