coil impedance

Nov 06, 2025 Last reply: 8 months ago 204 Replies

If this were true, you'd be able to come up with a reference to serious published papers on the subject. I found one on my first attempt (admittedly from back in 1959). All you could come up with was a page from the mouser web-site.

You presumably did enough to satisfy a customer, but none of it seems to have stuck.

Quantifying noise levels would be a pain. The nearest I've got to it has been comparing noisy traces on an oscilloscope - when you can get two traces with the same noise close enough to appear to be overlapping you've estimated the rms noise as half the separation.

In theory you bandlimit it, and multiply it by itself in a four quadrant multiplier, and low pass filter the product, but I've never seen anybody do it. At Cambridge Instruments there was a noise-limited resolution test carried out by the final test technicians who knew exactly what they were doing, but weren't all that willing to talk about it.

I once had to fudge a low pass filter to give them a signal they were happy with, and the discussion wasn't all that quantitative. I got home at about 10pm that night, and we shipped the first machine more or less on schedule.

I don't feel any need to insult you. All do I do is point out where you posts fall short. There's nothing childish about that.

Since the responses aren't composed to be insults, they probably don't satisfy the criteria for a "strong insult" whatever that might be.

Am 15.11.25 um 18:02 schrieb Gerhard Hoffmann:

Ingrid says I should add that:

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Gerhard

For very high resistances, thin film isn't practical.

A single atom thick layer of pretty much any metal has a pretty low resistance - high value thin film resistors have very long, very narrow convoluted tracks.

Thick film inks are pretty predictable mixtures of metal oxides and glass, and - unlike carbon composition - they haven't got a negative temperature coefficient and don't form hot channels.

One of my colleagues early on, was an intrinsic safety expert and his parlour trick was setting up a hot channel in a 10k carbon film 0.25W resistor and pushing an amp through it for some ten minutes.

It still measured 10k after he'd turned the current off but there was a narrow dark line along the surface where the paint had got hot above the hot channel.

You needed lots of volts across biggish capacitor to form the hot channel, but he'd got that worked out.

Thank Ingrid for me.

There is a third noise source, shot noise, from the fact that current is quantized to single electrons. Amazingly, thinfilm resistors have way below shot noise; the electrons queue up politely.

I theorized that thick film resistors would have shot noise but I couldn't measure any.

The Susumu thinfilms are fabulous. Even their cheap ones have below 10 PPM tempco in real life.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

A good insult, if such exists, would make sense.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

That would be one mile per day.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Am 15.11.25 um 19:26 schrieb john larkin:

:-) Ingrid was a lady in the German usenet who published endless sequences of auto follow ups. You could really watch her thinking in progress.

Gerhard

You will notice that I have moved your comment by one paragraph so that it now comes after my explanation of exactly what I did. Your post appears to have been done purely to be offensive and obfscate the facts.

Please stop behaving like a troll, you are in danger of driving useful contributors away from this group.

He's been doing that for years.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Not necessarily to you. Quite a few sound arguments don't make sense to you, particularly when they suggest that you might have got something wrong (which you experience as an insult).

Having a single set of fundamental units is a scientific orthodoxy. I've had enough trouble making sense of legacy units to think that it is a sound idea.

It's a derived unit. The unit of distance is the metre, the unit of tine is the second. The fundamental unit of velocity is the speed of light in a vacuum, and it is usually labelled "c" from Einstein's famous mass-energy equation.

People who get stuff wrong on a regular basis sometimes delude themselves that the world would be a better place if nobody pointed out their mistakes. Bridges breaking and buildings falling down don't make the world a better world.

If your performance is anything to go by, I wouldn't have liked working at any of them.

There are three patents and a few published papers that suggest that I can.

I have had occasional bad bosses, and I got made redundant from one job because a superior messed up one project badly enough to wreck it. If I'd been prepared to shift to a job as a staff engineer I could have stayed on, but went in solidarity with the rest of the team who didn't get that option. I've written it up here - with three years of my weekly reports plus some explanatory content. I'd hoped to do a Tracy Kidder job on it, but I don't have the necessary skills.

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The main reason that I moved around as much as I did was my wife's career, which was brilliant - she ended up as a FRS and a foreign member of the US academy of science - and I'd move when she got a better job.

People who haven't got scientific training do go for bizarre derived units. John Larkin did complete a science degree at Tulane, but it's pretty obvious that he only got what he thought he needed. Larrikins are like that

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One can understand how the family name got truncated.

Your explanation is an exact explanation of what you thought you did. The fact that you fixed on a specific bandwidth is clear evidence that you didn't actually understand the problem you were tackling. This may be an offensive observation, but it's hard to point out how somebody has managed to obfscate a problem without hurting their feeling.

We've always had plenty of trolls. The survivors are pretty thick-skinned. The more notorious trolls have been prone to describing people who disagreed with them as trolls. Cursitor Doom is perhaps the most obvious example

As has John Larkin. It hasn't worked. Jim Thompson claimed to have denounced me to the FBI as "dangerously anti-American" which would have ruined his credibility with them - at one stage I was cleared to "most secret" which was enough to get me into US Army ECOM when it was a Fort Monmouth, New Jersey.

You appear to have been interested in selected harmonic distortion whereas I was interested in total distortion (which includes noise). The former is more academic, the latter is more practical.

Do not worry, John Lu^Harking^H likes to play boss or something He has the highest level of off topic posts here AFAIK.

He flips if I give links to sciencedaily.org, then immediately babbles about shirts... clear sign of a minority complex obfuscation No wonder, designing for some idiots that do 'fusion power' research is something I would not do! .. 'Chain reaction' can be seen as a couple of compressed mechanical springs each hold by a thin fragile wire. Hit one and the spring releases and if other similar ones are around you get a chain-reaction until all those similar things have expanded. Fusion however is trying to press the strings back and keep them locked ,, You will, by definition, never get more power out (by releasing them again) than you put in there compressing them. So, it is 'merrica all over again, startups try it again and again with no usable result. Fusion.. Fusor, was done long ago, magnitudes below break even.

He is sitting there getting kids to build stuff complaining about 1 cent price differences in things that he maybe! sells 3 or 4 pieces of, makes no sense either, the electricity needed for posting here is more expensive. Telling us what we should do and say is a slily ego trip, this is NOT a moderated group,

Maybe it is the SF LSDs after effect, or the insane Tramp predcedent, that lowers the IQ of 'merricans. I can hardly wait for that King Kong in that Warhouse to disappear. Now it King K. is war mongering with Venezuela. Do you think I would cry if US got nuked into oblivion? Dirty war machine. Acting as war criminals in Gaza, many places, ... * People of the US = stand up against your King Kong monster leader = , may be you last chance. *

There is very little you can do about noise levels, apart from keeping the impedances low. Harmonic generation is more susceptible to careful design, and working out how much of each of the harmonics is actually present does help the design process.

If you have a controllable wide band frequency source, ideally producing separate in-phase and quadrature components, you can scan the frequency across the signal of interest and use two wideband four quadrant multipliers to multiply the in-phase and qudadrature components from the frequency generator with the signal and plot the products as the amplitude of each frequency component in the signal being looked at. This is what a classic low frequency spectrum analyser does.

Specifying a 5kHz bandwidth for the noise you will condescend to report is idiosyncratic.

This time it was Liz Tuddenham who was trying to exert her authority. John Larkin does try do it more often.

Jan Panteltje hasn't notice that we've got a fusion reactor hanging in the sky - we call it the sun - which gets loads of energy out of fusing protons together to make helium. As you look at successively heavier atomic nuclei up to about iron they get heavier each time you add in a proton or neutron, but not quite as much heavier as you'd expect from the weight of an isolated proton or neutron. It's called the mass defect and was known about even before Einstein published his mass to energy equation.

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that John did some work for is more about creating the conditions that exist inside a nuclear explosion than fusing hydrogen nuclei - they can do it, and have done it, but it is incidental to it's main job.

Expressing opinions about what has been said may not always be a silly ego trip

They last did it in 1776. We now have less violent ways of getting rid of a foolish leader. With any luck the Americans will be able to fake up some evidence that "proves" that Donald Trump was in on Jeffrey Epstein's child prostitution racket. Much cheaper than a revolution.

Couldn't happen to a nicer pussy-grabber. Getting rid of J.D. Vance might be harder, but maybe he will have enough sense to behave well enough not to put his job at risk. Of course, if he had that much sense he probably wouldn't have lined up with Donald Trump.

Sounds interesting. Lunatic fringe.

But I think my Larkin name is Irish and means something like groundskeeper or steward.

Sloman is derived from Slowman, meaning a tedious, pompous, deliberately offensive person devoid of humor or original ideas.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

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