Sensing small inductances

On a sunny day (Sat, 24 Aug 2019 23:31:00 -0400) it happened bitrex wrote in :

+/- 10 nH not quite sufficient +/- 1 would be better, but the two-variable, dual-frequency measurement technique I think will help a lot

The math is clever, I wonder what would happen if you used a bank of Cref capacitors and instead of a two variable, two unknown system you used e.g. four measurement frequencies and did the math on a system of larger order. would that improve resolution? accuracy? precision?

You'd end up with an over-determined set of equations and would have to use a least square multi-parameter error minimisng scheme to extract the most likely solutions (and confidence limits). I did that in my Ph.D. project - it should be easier now.

--
Bill Sloman, Sydney

Print and put in values.

Mikek

On a sunny day (Sun, 25 Aug 2019 11:07:04 -0500) it happened amdx wrote in :

Get a real monitor and /or see an eye doctor.

The great little AADE meter has an oscillator circuit that always oscillates, and a uP based frequency meter. It works very well for a simple instrument, and does a few nH pretty well. The schematic is online somewhere.

Making an oscillator is morally equivalent to boosting an inductor's Q, and has the same problems at low Q.

Inductors have ohmic losses and shunt capacitance that will fool any simple instrument. I like to connect a function generator and a scope across an inductor and sweep the frequency, to spot the region where actual L dominates, then park in the middle of that region and calculate L. And see the other stuff.

Really small Ls can be TDRd too.

Your schematics are unreadable. I don't even try.

On a sunny day (Sun, 25 Aug 2019 10:17:07 -0700) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

You could learn something, but WTF do I care, I do not use your products.

I'm often curious, but can not read them. Jan, why are they so dark, with such a poor contrast ratio? How do you even do that?

--
 Thanks, 
    - Win

Q is a function of frequency so whether the inductor needs its Q boosted, or not, depends on what frequency you want it to oscillate at.

Most simple oscillator circuits don't tend to have enough loop gain to make random scramble-wire inductance that might have a self-resonant frequency in the hundreds of MHz ring reliably in a resonant tank down at single-digit MHz frequencies a cheap uP could handle with its (cheap) on-board peripherals.

A couple topologies like say the Pierce with things tuned exactly right seem to sometimes, but naturally at simple instrument. I like to connect a function generator and a scope

Both fine techniques for the bench but not workable for a production-thing with a tighter budget.

However what I'm mainly interested in being able to detect relative differences between random-wires inductances with precision, and less concern about absolute accuracy as compared to some reference standard.

they're not that bad.

I've seen way worse, at least.

these dudes just being dramatic.

engineers looking at schematics like good gracious! why it's just awful! /hand to forehead, swoon

I thought women were supposedly the dramatic ones

On a sunny day (25 Aug 2019 10:38:32 -0700) it happened Winfield Hill wrote in :

I dunno, I have no problem reading those in my browser, or Linux 'xv' viewer or whatever,

Often I wonder (video is my background) if people even know how to adjust a monitor, These pictures are of schematics I use to build the stuff, so 100% of info is there or it would have to be so obvious I omitted it. I do not sell kits. All the babble .. read the asm source it clearly shows in ASCII what is connected to what. If anybody actually builds this thing they can ask. The explanation text in the link I gave is 100% simple for anybody known in the art,

And if you cannot read it or understand it, so be it,

As to the art, if you cannot read a component value and understand what sort of magnitude say 'resistor' must be there you need to do more experimenting, not so many silly simulations.

Next somebody will say: 'Oh and I cannot read PIC asm..' There is no end to not understanding somebody once wrote something like 'hydrogen is the most present thing in the universe but for stupidity'

different versions of it.

I am not referring to you, I know you know the stuff. Jo.La. has a bunch of payed slaves working out details for him... Some other one is into crystal radios and refuses to look up super-heterodyne even offered me a deal LOL. No hope there.

Hawaiian War Chant

:-)

I thought engineering drawings were supposed to be clear and precise. I assume he draws like that on purpose.

ps - your misogyny is apparent again

Very well paid slaves. We design things together, and we share clear, precise drawings.

Each project has a responsible engineer, which is sometimes me, usually someone else. We create a project folder on a shared server, where we leave a design notes folder for sharing ideas now, and for future reference.

Sure, sometimes I get help on my projects, and sometimes I help people on theirs. It's fun and we all learn stuff.

We also document all breadboards and experiments. Clearly.

You can read your drawings because you are intimately familiar with them; we aren't and can't.

On Aug 25, 2019, Jan Panteltje wrote (in article ):

If you tell your camera that the picture is largely white, it will take far better photos (by rendering the paper as white, versus 18% gray). Sometimes one must lie to the camera to get it to do this, but a few experiments will tell the tale.

Joe Gwinn

Use a good pen or pencil on white grid paper, and draw and letter carefully.

I had to take two semisters of engineering drawing in college. We all hated it and it was very valuable.