Measuring the capacitance of an inductor or Inductors

[soundmasterg]

Let's forget this "disturbance in the force" (I mean field) crap. That is for star wars. Pickups work according to Maxwell's equations, one of which is the law of magnetic induction.

Give yourself to your destiny and you will discover the TRUE POWER of the dark side of the force.

Greg

[Possum]

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Yes, alnico 6, the magnet of Lucifer, hammer of the Dark Gods....

[Mike Sulzer]

You Mac inputs probably are too low impedance. Use op amp buffers.

Scientific notation is easy once you get the hang of it.

10 = 1x10^1
100 = 1x10^2
1000 = 1x10^3

4000 = 4x10^3

Going the oher way , you have to be careful:

1 = 1x10^0
.1 = 1x10^-1
.01 = 1x10^-2

it is convenient because:
1x10^6 times 1x10^7 is 1x10^13
1x10^6 times 1x10^-2 is 1x10^4

If you multiply 4x10^5 times 3x10^4 you get 12x10^9, which is also 1.2x10^10. It is convenient to keep that number between 1 and 10.

[Possum]

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I think I get so 10 with the little 11 is ten times ten 11 times, my calculator goes into error mode I don't see how to do that one on my scientific calculator, maybe Joe made a mistake?

[Possum]

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My calculator is Texas Inst. TI-30xA I don't see anywhere that it will do 10 in anything except 2 (squared). Is this called "powers."? They don't show it doing anything like that, or I'm just too dumb....

[Possum]

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Also with the Mac I am fully getting screen viewing of the frequencies in full detail, there just aren't any perfect peaks viewable, and the one that does show up is at 1khz. I could try running the pickup through my Behringer mixer, would that help?

[Mike Sulzer]

I think I get so 10 with the little 11 is ten times ten 11 times, my calculator goes into error mode I don't see how to do that one on my scientific calculator, maybe Joe made a mistake?

Enter 10^11 as 1 followed by 11 zeros. Capictance of a pickup should be something like 6x10^-11. Remember .01 is 10^-2. (That is, start with 1, which you can think of as 1.0, and move the decimal point two places to the left, adding a zero as necessary, to get .01.)

[Mike Sulzer]

Also with the Mac I am fully getting screen viewing of the frequencies in full detail, there just aren't any perfect peaks viewable, and the one that does show up is at 1khz. I could try running the pickup through my Behringer mixer, would that help?

if it has a very high input impedance input, that should do it.

(If you have a sci. calc., you can enter a number in sci. not. very easily, like 1.6e-11, where "e" is some key that might be marked "ee" or something, and it stands for "times 10 to the".)

[David Schwab]

Also with the Mac I am fully getting screen viewing of the frequencies in full detail, there just aren't any perfect peaks viewable, and the one that does show up is at 1khz. I could try running the pickup through my Behringer mixer, would that help?

Does the mixer have a hi Z instrument input? My Behringer only has line and mic inputs. The line inputs are low z.

Do you have any Boss or Ibanez effects pedals? If they don't have "true bypass" they will still buffer your input signal when in bypass mode.

[Joe Gwinn]

My calculator is Texas Inst. TI-30xA I don't see anywhere that it will do 10 in anything except 2 (squared). Is this called "powers."? They don't show it doing anything like that, or I'm just too dumb....

This TI calculator does understand Scientific Notation, but you have to set the mode to SCI:

Solution 10698: Setting Scientific Notation Mode on the TI-30Xa, TI-30X IIS/B, TI-30XS MultiView™, TI-36X Solar and TI-36X II.

[Joe Gwinn]

OK for the retards among us, me being chief retard, I dug this back out, Joe's method. I tried it again and now it seems to work, maybe I used the wrong resistor. So, I plodded through the whole equation to get to C. I had an inductance of 3.957 Henrie. A peak res frequency of 6.2khz, and a coil resistance of 7.721K.

I get 166.5 pF for the coil self-capacitance. This is plausible. but seems a bit high.

Calculated Q was 19.91. That seems awfullly high unless its Q at the resonant frequency? At a 1khz on the Extech Q is about 2.5.

Q will vary directly with frequency, and these two values of Q are both correct enough. I get Q= 20 at peak amplitude frequency and Q=3.2 at 1 KHz.

This is a real pickup, so I ended up with a number something like .0000000066, there may have been more zeroes in there. I don't know what 10 with the small 11 Farads next to it in the final part on the bottom really means, but it just looks like it means x 10 according to the answer he got. if thats true then my answer was still infinitesmally small, and I don't know what it means. I tried some online calculators and end up with huge numbers, so that was no use. The pickup is a '63 Patent.

Something is wrong. For the record, 0.000,000,006,6 Farads is 6.6 nanofarads, which is way too high for a pickup, although a long cable could manage such a value. Or, some zeros were lost in the shuffle.

With the calculator set to use scientific notation, loss of zeroes should no longer be a problem.

I did try the resonant frequency hookup and happened to have a 1meg ohm pot laying around that I used, so I got readable peaks from buckers and strats. Now if I hook up my computer oscilloscope programs across the 1megohm pot it won't read any peaks at all. Using a driver coil and hooking the pickup straight into the Mac's line in I don't get any readable peaks either. So how DO you hook this up to an oscilloscope program with line in on an oscilloscope or audio input?

And what IS the capacitance of my '63, my results don't make sense.....

As others have noted, most likely something is wrong with the setup.

[David Schwab]

...although a long cable could manage such a value.
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As others have noted, most likely something is wrong with the setup.

I think he is plugging into the Mac's audio input, which is more than likely low Z. That would explain the apparent loading.

[RedHouse]

OK for the retards among us, me being chief retard.....

No man, only visions a gradeur, you are in a group of equally retarded peers here! and I don't think there is a cheif, perhaps a big council of lead retards if anything.

Off-topic alert! ...funny coincidence though, I heared just the other day on the radio that some group is trying to make the word "retard" a non-pc faux pas as it is thought to insult actual retards. The commentator asked the person being interviewed why, commentator says: "no one calls a real retard, a retard, they call someone exibiting virtual retard'ness a retard so how does that effect real retards?" the dialog made me laugh.

[LtKojak]

you are in a group of equally retarded peers here! and I don't think there is a cheif, perhaps a big council of lead retards if anything.

Oh boy, do I feel at home here... (waiting for jonson's punch line)

[Possum]

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The pickup is absolutely fine, not a thing wrong with it or the LCR meter and DMM would give weird readings, which it doesn't. 6.2Khz seems odd to me for a 7.78K humbucker. The lead on it is only 3 inches long. AC resistance at 1khz is only 10.8, right in the pocket for a PAF. The DMM was connected to either side of the 1megohm resistor, is this correct?