coil impedance

I measure 42 ohms DCR and 220 uH, a couple of ways.

But the effective inductance, that predicts the voltage given some current through the loop, is way less, so low it's hard to resolve.

I ordered a mono car audio amp (claimed 1500 watts!) so I can push some more amps through the CT and get more output.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Pure plagiarism, of course.

You can't train your instincts - they come from your genome. You can train your expectations which come from your subconscious.

If you thought about what you were doing, you could generate rational expectations, but that takes the kind of intellectual frame work that university education is intended to provide, but you did have to be paying attention during the relevant bit of your course.

If you've got access to the relevant textbooks you can get it from them, but not everybody can manage that.

There is no such thing as a "typical number". Pretty much every coil has a different size, a different number of turns and uses a different wire gauge. Real examples are useful, but only when they give all the data, and that is pretty much the complete design (which is what you are trying to pirate).

If you dug into the academic papers you'd probably be able to find the detail, if you understood what the paper was saying.

That's not "the effective inductance" but rather the mutual inductance with the loop around which the current you want to measure is flowing. It is calculable.

It's peak output, rather than sustained output. Nobody wants their ears hammered by sustained loud noise.

The moon landings and the international space station did what they were intended to do. The fact that you think that they shouldn't have spent the money doesn't make either of them any kind of confidence trick.

Jan Panteltje has a similarly imperfect understanding of what ITER is supposed to do. Deaf people can't see the point in a symphony orchestra.

There's a big gap between a pre-production prototype and a product that works reliably enough to sell. Frequently the people who engineer the pre-production prototype don't understand how big that gap is.

It's a couple of atoms. The University of NSW quantum computer relies on an individually implanted phosporus atom for each q-bit.

Somebody will eventually want to put it in just the right place in the array of individual silicon atoms.

Google picks up everything, including a lot of American wishful thinking.

Not making stuff was a British disease - actually a home counties English delusion. Margret Thatcher did grow up in Grantham (which isn't quite home counties). The Dutch are primarily a trading nation, but Philips was still making a lot of stuff when I was there, and Airbus is still out-manufacturung Boeing

Maybe if you had paid more attention to them you'd have realised that they aren't quite as forgettable as you like to think.

You never learned enough to realise what was actually being said

Some sciences look like that to people who don't know enough to understand what's going on.

But you didn't pay enough attention to realise that the Swiss have invented quite a lot.

Trump has just back-tracked on a lot of his sillier tariffs, but he's still got plenty of other projects which strike objective observers as likely to wreck the country.

He's a disaster, and a lot of Americans, you included, haven't yet noticed.

Probably not. Venture capitalists will fund all sorts of bizarre design projects, but the aim is to put something together that will sell like hot cakes, rather than something that works better than the competition and will keep on working better until it wears out.

I got exposed to that with the Lintech electron beam tester which sold like hot cakes until Schlumberger hired an ex-Lintech engineer to build a chinese copy with added extra reliability. Lintech never sold another machine after his version hit the market.

It's not a good example, because Lintech was English and Schlumberger was American. In this case one Englishman had learned all the wrong things from the US, and a US firm exploited the opportunity he created.

Bell Labs provided a better example when they developed and sold a shaped-beam electron-beam-microfabricator to European Semiconductor Structures in Aix-en-Provence. It never delivered more that 10% of the promised writing speed, and the buyer went bankrupt.

I got that bit of the story some twenty years later when my wife got to be a fellow of the Royal Society of London and during her introduction to the society, I got to talk to the guy who had been running European Semiconductor Structures when it went bust.

I know he didn't have an EE degree - neither do I - but that doesn't mean that he ran on instinct. I once bitched to him about an app note on Peltier junctions that didn't give the equation for heat transfer (which is very non-linear) and he fobbed me off with the Steven Hawking line that each equation in a book halves its readership.

He was writing application notes, rather than a mass market book, so it wasn't much of an argument.

Don't be silly. Hypersonic aircraft still fly within the atmosphere, if a little higher than sub-sonic aircraft.

Where the air is less dense, there's less air resistance - also less lift - so you have to fly faster to generate enough lift to counter-balance gravity.

Unfortunately hypersonic aircraft end up having a high surface temperature in flight, which complicates life no end. Creating a shock wave might be seen as producing turbulence, but the airflows in a shock wave don't have much in common with what you see in sub-sonic flight.

There still seems to be a big gap between any faintly practical hypersonic aircraft and escape velocity.

You needed to look that up?

You missed the "beanstalk". You ship stuff up to a synchronous orbit and built up and down to make a very long synchronous satellite, until the bottom end hits the ground, where you anchor it. After that you can ship stuff up the beanstalk to put a little bit of extra tension on the stalk, then you add an elevator that climbs the stalk until it get to the synchronous orbit level or higher and launch stuff into space by letting drift away.

Diamond filaments might work, but they are even further off.

And AI might even tell you that it could be done - it makes mistakes from time to time. Apparently the current versions are trained to tell stories that make reader happy while the story is being read. More accurate stories seems to be less likely to make the reader happy.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The magnetic field around a current-carrying conductor drops off as 1/r. The bit of wire of each turn closest to that conductor gets a tiny bit more voltage induced in it than the part of the turn that is farthest.

So, yes, the induced signal is tiny, but if you want to measure kiloamperes, that's a virtue.

Jeroen Belleman

Off by an order of magnitude! Two hunderd and fifty thousand miles per hour.

Jeroen Belleman

Erm, no, I messed up. Jan was right.

Jeroen Belleman

The Rogowski coil data sheets typically claim that position errors are under 1%.

Maybe I can charge a cap and discharge it through a R+L and get a big current peak. I can measure the voltage drop across the resistor and calculate current; I think I can do the math on that one.

We have some mosfets in stock that are rated for 1000 watts and 1000 amps peak.

In fact, I have the resistor-blaster rig that H+H used in their X-chapters. That makes big pulses.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

One gotcha is that if a vehicle has lots of less-then-escape velocity before it exits the atmosphere, it will be in an elliptical orbit, so will dip down again soon.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It would be much more fun if you could get hold of the equipment they used to magnetise magnets: a BIG high voltage capacitor and a thyratron.

In fact I've got a pretty clear idea of what she did - probably better than she has - and it was irrelevant to that particular bit of the thread. Pointing out that somebody has screwed up is going to be offensive to them, unless they are more interested in not screwing up rather than in being admired, but it isn't nonsense.

For which I'd be profoundly grateful, if the Math Student lived up to their word. In practice ostentatious offense takers find lots of excuses to take offense.

My customer tested their cap banks with dummy loads switched by ignitrons.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics