I have a P-90 magnet question...

[Rosewood]

Yes, but it's a bit rough.

http://home.comcast.net/~joegwinn/

Look for "Simple hall-effect magnetometer".

Joe, is this on a test board or is it in a box ready to use. Wasn't sure what you meant by rough, as in looks or operation. Good job regardless.

[Joe Gwinn]

Joe, is this on a test board or is it in a box ready to use. Wasn't sure what you meant by rough, as in looks or operation. Good job regardless.

It's rough in the sense that one needs to have a digital multimeter, and to fiddle with adjustments. My prototype is built on a small piece of perforated vectorboard. It is not in a box.

It also saturates at 1000 or 1200 gauss, which is slightly low for some pickups.

Within these parameters, it works perfectly.

[SkinnyWire]

There is really only one gauss meter that we all use here ...

Not true. I use this one with an axial probe. Very nice meter.

[LtKojak]

Not true. I use this one with an axial probe. Very nice meter.

Which one?

[belwar]

my apologies . I should have said that in general people here use the 200a with some exceptions

[SkinnyWire]

If this is the case then why did Shea at magnetic hold tell me that I could store all of my magnets in close proximity? In theory I aggree with your statement, and that is why I asked Shea in the first place, but would it take months, years, decades, or longer?

I know that there is not a perfect answer, but if it there is any transient demag or weakening due to design of a pickup that sounds like a poor design to me...

Depends on what you mean by "close". You get an A5 magnet too "close" ... I'd say even as "close" as 2 inches ... to a another magnet and the field strength "could be" altered - especially if it's a much stronger magnet. Might be, might not be. In like orientation, it may skew the poles to one side. In opposing orientation, it might knock the strength down a few 10s of Gauss or a hundred and impacts on one pole may translate to the other pole to some degree. The other grades aren't quite as sensitive. You can store the bricks "close", but just pulling a magnet off the brick can impact the strength and uniformity of the field across the pole faces. Here again, the amount varies from magnet to magnet and it might, might not have a big impact.

P-90s are what they are and have been around for a loooooooong time. The instant you assemble them, the magnets are "different" than what you started with. A5 being susceptible to self demagnetization would give rise to the previously mentioned discussion regarding mixed magnets. In general, magnets may lose their strength slowly, but in response to manipulation things happen in an instant. The only way to know how something like this would work is to set up a mixed example yourself and monitor it over a period of time to see if there's a trend.

[SkinnyWire]

Which one?

http://www.trifield.com/gauss_meter.htm

[David Schwab]

http://www.trifield.com/gauss_meter.htm

That's a nice looking meter.

[SK66]

Has anybody made their own gauss meter?

I have, might still have the diagram for it...It was a airly involved circuit with buffer and zeroing etc. I still have many of the parts to make it "neat".
This was the finished product...a little smaller than a cigarette pack.
http://www.skguitar.com/SKGS/sk/Images/gmeter.jpg
Here is a simple diagram on page 34 of this pdf http://www.allegromicro.com/en/Produ...an/an27701.pdf
It uses an allegro calibrated sensor. They talk about using the circuit and calibration chart that is supplied with each sensor for very accurate readings using a voltmeter.
I now use a F.W. Bell Gauss/Tesla meter....I found it for a very good price and I wanted "real" data. My creation gave "relative" data.
In reality though. A gauss meter isn't a necessary tool to have.
Some field viewing film and, or, standard "pull/lifting" test is just about as reliable/usefull.

[SkinnyWire]

I have, might still have the diagram for it...It was a airly involved circuit with buffer and zeroing etc. I still have many of the parts to make it "neat".
This was the finished product...a little smaller than a cigarette pack.
http://www.skguitar.com/SKGS/sk/Images/gmeter.jpg
Here is a simple diagram on page 34 of this pdf http://www.allegromicro.com/en/Produ...an/an27701.pdf
It uses an allegro calibrated sensor. They talk about using the circuit and calibration chart that is supplied with each sensor for very accurate readings using a voltmeter.
I now use a F.W. Bell Gauss/Tesla meter....I found it for a very good price and I wanted "real" data. My creation gave "relative" data.
In reality though. A gauss meter isn't a necessary tool to have.
Some field viewing film and, or, standard "pull/lifting" test is just about as reliable/usefull.

While I can't argue the value of real data, I'd argue that relative data is sufficient here. I always point out to folks that ask me about magnets that what I can provide is relative data. This normally centers around something like "I wan't a copy of the Duncan EVH pickup, which has a 20 Gauss alnico 2 magnet ... blah, blah". You might hold a sticky note on the fridge with a 20 G magnet, but that's Seymour's relative strength measurement based on one of those old -50-0-50 analog magnetometers run across the face of the completed pickup ... something like that.

That said, I believe you're also correct that pull/lift testing may be sufficient and as reliable/useful. That's what prompted me to buy a Gauss meter in the first place - the magnets I was pulling from a brick just didn't seem to pull as hard as they should so I was concerned they were weak. They were, and the Gauss meter gave me the warm fuzzy of numbers, in a relative sense, compared to what I trusted were fully charged magnets of the same grade.

It's all relative.

[Possum]

...

The AlphaLab gaussmeter is the one I got, its a nice meter, downside is the cord always gets twisted up and last year the Hall sensor died, $80 to replace it, ouch. But it is super sensitive and the sensor tip will go into spaces nothing else will......

[Zhangliqun]

You're going to get SOME degaussing whether you use the same Alnico grade or not. I was talking to another winder a while back and he said that over time, one magnet will become more dominant than the other.

So I figured that instead of taking that crapshoot with an unhappy customer down the line, it would be better if I decided in advance WHICH magnet would be dominant, so I could determine which harmonic node of the string over the pickup would be emphasized. So sometimes I mix a nearly fully charged A5 with a partially degaussed one, or I mix A5 and A2. Again, you'll still get degaussing over time, but my theory is that by predetermining the strong/weak mag relationship, the basic tone flavor won't change near as much.

[SkinnyWire]

The AlphaLab gaussmeter is the one I got, its a nice meter, downside is the cord always gets twisted up and last year the Hall sensor died, $80 to replace it, ouch. But it is super sensitive and the sensor tip will go into spaces nothing else will......

Yeah. The cord is a bit of a PITA sometimes. I got the axial probe, and so probably lost a bit of sensitivity but I thought it might be a bit more "robust". It's basically a PVC cylinder about the size of a pencil with the probe epoxied into the tip end. The folks at AlphaLab have always been real helpful too when I've called with questions about using the meter.

[kevinT]

http://www.trifield.com/gauss_meter.htm

I really like that gauss meter with the probe. You can more precisely take a reading of the magnet. It's also about the same price as the CM meter.

[Peter Naglitsch]

I finally took the plunge to get myself a "real" Gauss meter (the AlphaLab DC Gauss meter Model 1) although I have earlier stated that I would stick to my traditional R B Annis. Now I'm in the process of "translating" my old, incorrect measurements into some real world numbers. But I can testify to the above: After a few weeks use the AlphaLab still seems to be a really good meter although the cable is always some were that you do not want it to be...