This talk about Q meters got me thinking. What's the most useful test equipment?

[SK66]

For me it's a signal generator and basic voltmeter. If it's a known design I just count turns and make sure there's no shorts (expected dcr, etc). For new designs and occasional "checks" it's the signal generator. With it hooked up to a driver coil I measure the AC output of the pickup throughout the entire range of signal output. This gives me a very "visual" description of the pickups character. Harsh or smooth, focused response or flatter curve, full or harsh, bright or dark, etc etc.
I've never found a bad pickup measuring inductance/Q/etc that didn't also show an anomaly in one of those two pieces of equipment. i.e. odd dcr, continuity between pole/coil, weird signal "notch/spike" or completely unexpected response curve.
I have a lot of test equipment, mostly expensive stuff, Tenma digital 2 channel scope, Wandel Golterman digital signal generator/line tester (pretty cool), fluke rackmount multimeter, genrad rlc digibridge, another wavetek signal generator (never used any more), Bell gauss/tesla meter, ferrofluid, ferro film, etc.
The Wandel Golterman is used mainly as a signal generator, but has the ability to also compare the signal the pickup is generating to the signal it's exposed to and any noise level the pickup adds. Cool idea, just wish I had the damn manual.
Still the most useful is the handheld ohmmeter/voltmeter (also fluke, sits next to the winder) and the signal generator. All the other tests are kinda just numbers compared to other numbers, and I have hundreds of pages of "specs"...but the ac output curve is "descriptive" and quite "telling".

Don't get me wrong, if you're inquisitive and have the money, buy all the equipment (I did). The information gained can only help...but in the end I found it all to be basicly "relative", Inductance being the most useful "spec" of all the other measurements, but still "relative".
I did full "bench tests" of all specs for the second/third/maybe forth hundred pickups (the first hundred or so I didn't have all the equipment) and I also played them all...Gave me a good understanding of how things interact (maybe "feel for" how they interact is better because I can't define it in absolute terms even today).
Now I only test for shorts and maybe inductance (usually first couple with a new spool of wire). Occasionally I make "spot checks" for output curve/install in the test guitar when working with known designs. The rest of it is just there for testing a rare/special pickup and new designs.

[Possum]

........

So you just run the signal generator to drive the coil and measure the AC voltage generated through the spectrum? You said "visual" of the output, are you charting the numbers from the voltmeter?

[R.G.]

So you just run the signal generator to drive the coil and measure the AC voltage generated through the spectrum? You said "visual" of the output, are you charting the numbers from the voltmeter?

Hey... isn't that kind of what I was suggesting with measuring pickup response curves a ways back?

Hmmmm...

[NightWinder]

Thanks for sharing that SK- Looking forward to learning some new methods and such-

[SK66]

So you just run the signal generator to drive the coil and measure the AC voltage generated through the spectrum? You said "visual" of the output, are you charting the numbers from the voltmeter?

Yes, that's how it's done and yes I will chart the numbers. If you use a simple graphing program it makes things very obvious.
I don't worry that the testing may not be "standardized" with other manufacturers....there is no such thing as "standardized testing" in this industry.

[Yves]

Actually, there is a brief describing some process, which I believe is the same approach that the one you use SK, along with some picture of the coil used for that purpose, here:

http://www.buildyourguitar.com/resou...emme/index.htm

Yves.

[Possum]

RG....

no this is different method, AC resistance, AC voltage, the other method is to use a spectrum analyzer, charting software, I don't think it operates the same way. Joe Gwinn had a similar method of hooking the frequency generator directly to a pickup and a resistor and reading voltage across the resistor to find peak resonance, trouble is it didn't work very well with hand wound pickups that can have very smooth peaks so you kinda got lost trying to find it. I kinda like SK's method because it deal in numbers not lines on paper. Simple. Yes there's no standard way to measure any of this, if it works for your needs that all that I care about...

[SK66]

Actually, the Lemme analyzer is the same in principle. I originally considered buying his analyzer, but the cost was prohibitive and for about the same money (or less) I bought 2 very nice pieces of equipment(used) which can also be used for other things. If I want to check with resistors (pots), caps, cables I just connect them in series with the pickup.
It doesn't look like he's selling it anymore, but I think the cost was around $700.00 back then.

[Béla]

Computer sound card output running into a coil stripped from a 2$ earphone, the coil above the pickup, output going into a HighZ input, back into the PC.
Software used is a registerware(don't worry, wont send spam) called RoomEQWizard.
Makes nice graphs like this:


Oh, and in case you need an integrator, just use this calibration file: http://www.mediafire.com/?k3zjuzbyzh9

[Steve Conner]

Ooh, that's awesome Bela! I've used that FFT analysis method for designing tone controls, but never tried it on pickups. Also, I didn't know about RoomEQWizard, I was using other software, but it doesn't work on my new PC. Thanks for the tip!

[Joe Gwinn]

Joe Gwinn had a similar method of hooking the frequency generator directly to a pickup and a resistor and reading voltage across the resistor to find peak resonance, trouble is it didn't work very well with hand wound pickups that can have very smooth peaks so you kinda got lost trying to find it. I kinda like SK's method because it deal in numbers not lines on paper. Simple. Yes there's no standard way to measure any of this, if it works for your needs that all that I care about...

The problem is inherent -- low Q pickups will have very broad peaks. For this, one must instead use the phase method (the one with the Lissajous figures http://en.wikipedia.org/wiki/Lissajous_curve). Although if the peaks are that broad, the exact resonance frequency isn't much use unless one is trying to pick values of R, L, and C that approximate the actual pickup's curve.

Plotting the response spectrum and looking at it will certainly tell if one is in the ballpark, and will also (as mentioned by SK) easily detect shorted coils. The spectrum as a table of numbers also works, although I prefer to look at plots.

[David Schwab]

Computer sound card output running into a coil stripped from a 2$ earphone, the coil above the pickup, output going into a HighZ input, back into the PC.
Software used is a registerware(don't worry, wont send spam) called RoomEQWizard.

Ooh! Runs on Mac OS X too! OK I have to check this out.

[Possum]

OSX

Let me know if it works on your Mac, looks like you may have to mess with Java stuff to make it work, if your Mac doesn't blow up I may try it here :-)

[David Schwab]

Let me know if it works on your Mac, looks like you may have to mess with Java stuff to make it work, if your Mac doesn't blow up I may try it here :-)

I haven't tried it yet, but I checked out the Java thing... I'm running Leopard (OS X 10.5.2 for the non-Mac heads) and it uses Java 5.0 as standard. It has a preference app that let's you switch between that and some old version like 1.6 or something.

Apparently Tiger (10.4.x) might not be using the newer version as the default and you have to tell it to do so.

I'll give it a launch right now...

OK.. doesn't blow anything up. It also seems to be having an issue finding my M-Audio sound card.

I have Tiger installed on my second hard drive for running Pro Tools, so I'll try it there this weekend.

[Possum]

10.4.10

I downloaded the program and running 10.4.10 I have Java 5, something isn't working right the generator frequencies sound screwed up and weird....