LCR meters - importance of Q?

[chevalij]

I was looking at a new meter. What is the importance of Q and how would you relate it to your pickups?

[Possum]

........

Its only important in a relative way as all the readings on an LCR meter are. If you're tryiing to hit a mark its important, if you want to see the difference between two pickups you made then its important. It doesn't mean anything by itself until you listen to the pickup. You also have to look at the other readings and see what they are doing in relation to Q, inductance, AC resistance. those are the 3 important things to consider. they aren't all related proportionally, if you add a big chunk of steel to your recipe you'll see inductance go down and AC resistance go up, and I think Q goes down as well. You just have to use it alot to know what it means really, and don't forget on the Extech to have it set to "series" readings, not paralell.

[David Schwab]

What is the importance of Q and how would you relate it to your pickups?

Q is needed when you have to make a pickup that is also a flame thrower or maybe converts into a life boat.

(not so obvious James Bond reference..)

[SK66]

Of all factors, The only one I would use as my "benchmark" would be inductance. The other factors are important, especially in telling you if something is wrong, but inductance is the one I associate with a tone. That's just my opinion, and fwiw, I don't test every pickup I make.

[Scott S.]

It might be a little meter dependent (I use an old school ESI impedance bridge), but I notice a huge change in Q if there is something wrong.

Case in point, just the other day, wound a pickup that is supposed to measure out at 4.18 - 4.22 H and Q of 2.8, but got a bad wind (obviously had a shorted turn) that measured 3.8 H and Q dropped all the way to 2.0

I measure every pickup, and find my results to be very consistent if I get a good wind. For instance, I rewound the one discussed above , and got 4.21H and Q of 2.77.

I see an impedance bridge to be as important for pickup building as an oscilloscope is for building electronics.

[chevalij]

Thanks for the input guys. My basis for the question was when buying a new meter if I should bother with a higher end meter that does Q, or if a basic meter with inductance readings would suffice. Of course, the cheap ones have no selection of freq. Is that important, or do you find your readings the same at 100Hz and 1k?

[Scott S.]

I always use 1 KHz, and you are comparing to other reading typically so that is not too big of a deal probably.

I would say you definitely want Q, and keep in mind there are a very limited number of digital LCR meters that work properly with pickups. Do a search here, there is an Extech that works and not many others.

I use the older analog version of LCR measurement called an impedance bridge, google or search ebay for impedance bridge and you can see what it is. Any General Radio or ESI impedance bridge will work perfectly for pickups.
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Later Edit

I popped over to ebay and there are many usable ones sold recently for under $100. As long as you buy one that works, no worries, since the measurements are comparative it doesn't matter if the calibration is a little off.

[soundmasterg]

Yeah, we went through this about 2 years ago on the old board and most of the meters don't measure inductance accurately with guitar/bass pickups. The Extech 380193 meter does, which is why everyone uses it. The Rickenbacker company uses it and I'm sure others do too.

Greg

[SK66]

I use a digibridge..pretty expensive. FWIW, I'd say either stick with a basic Ohm meter or buy the Extech 380193. It's not that awful much more than a really good ohm meter and if you're really into "measuring" then you're eventually going to wonder what you're missing and look for one with Q later.
Different measuring voltages isn't necessary, but can give additional information if you are really curious...

[chevalij]

Yeah, we went through this about 2 years ago on the old board and most of the meters don't measure inductance accurately with guitar/bass pickups. The Extech 380193 meter does, which is why everyone uses it. The Rickenbacker company uses it and I'm sure others do too.

Greg

Would it be the high dcr that throws off a normal meter?

[soundmasterg]

I don't remember what the consensus was as to why you needed a specialized meter for pickups and normal meters don't work accurately. It was all in that old thread, but who knows where it is now. Maybe someone else remembers....

Greg

[Dave Kerr]

Joe's take on the Extech

[chevalij]

Interesting. Of course, inductance is resistance to AC, so I can see why putting a resistance of any other kind could be interpreted as inductance and would of course throw off the meter. Unless my logic is faulty, it appears any cheap LCR meter would work (as long as you don't put a pot in front of it). What does an Extech see once the pickup is in the guitar and the volume pot is adjusted? It seems to me that it's readings would go all to hell as well....

[David Schwab]

Of course, inductance is resistance to AC

That would be impedance.

Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases.

The definition of inductance is:

An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. The ratio of the magnetic flux to the current is called the inductance, or more accurately self-inductance of the circuit.

Then of course we have reluctance...

Magnetic reluctance or "magnetic resistance", is analogous to resistance in an electrical circuit (although it does not dissipate magnetic energy). In likeness to the way an electric field causes an electric current to follow the path of least resistance, a magnetic field causes magnetic flux to follow the path of least magnetic reluctance. It is a scalar, extensive quantity, akin to electrical resistance.

and after reading this stuff... big headache!