Magnet Pull test VS Gaussmeter (any opinions?)

[Folkcafe]

First I hope this is the correct place. I did a search on testing magnet strength and found an engineering forum with a discussion about the best way to test magnet strength. There were mainly two schools of thought on this but the consensus was that the appropriate test varies based on application.

So I am looking for some insight for my limited application. Currently I only want to test for consistency with single coil magnets. Getting an accurate Gauss measurement is not needed at this time. I only want to be able to test that I am getting a reproducible result or to be able to measure variances in magnet charges while I'm in this experimental phase.

I looked into what a test kit consist of for pull testing and it is really just a weight scale with various hardware to attach to the scale. I have a number of spring tension test scales that I could probably adapt from my days of repairing electro-mechanical equipment like VCR's, reel to reels and such. Like I said, I don't care if it is not calibrated to a Gauss scale, so long as I can get a scale that I can use for prototyping purposes. Later once I decide what my needs are, I can look at purchasing a Gauss meter.

On another note. I have seen F. W. Bell 620 Gauss meters for sale for fairly cheap. Would this be a suitable meter for pickup purposes? Which style of probe should I be looking into? If not, what test range should I be looking at?

I know, a lot of questions but I was not finding much from searching either the forum or the web. Seems like most of the discussion on the web is centered around EMF or micro Gauss geological testing.

So thanks in advance for any and all possible opinions. This is a new community for me and I don't want to wear out my welcome.

Don

[ShannonH]

don't sweat it

As long as you aren't a troll, I can't see you "outwearing" your welcome.

I don't own a gaussmeter. I just don't have the coin. I can see how the device you indicated would be useful though. It's a mechanical way to measure the magnetic force. Now I want one.

Shannon

[pete n]

Has anyone tried building this? It sounds like it might be a possible gauss meter without spending a ton of money.The Attack Gaussmeter

[jwendt2003]

...probably the same as this one too...
Build your own Gaussmeter

[tonedeciple]

I'm going to build this simple "gauss meter" as soon as the parts I ordered arrive. However, I have no illusions as to it's accuracy. IMO it's a slightly higher tech version of an RB Annis gauss meter.

What I do hope to achieve is a number which I can assign to a tonal range for a given magnet. In other words, I'll charge and degauss a couple of alnico V mags to different levels, record the readings from the meter and see what each sounds like in the same pickup. Then, I'll repeat the process with a couple more mags at the same levels as before to see if my process is repeatable. If it is, I'll have a reasonably accurate way of determining how a magnet will sound after it's charged/degaussed and before I make the pickup.

BTW, this test will be done with alnico bars for a humbucker PU in a room that has a consistent temp.

[David King]

One thing I can say in favor of owning a calibrated gauss meter is that when you post your results here or read other people's results here you will be able to compare apples and apples.
The total cost of Elepro's group-buy extravaganza Gauss meter last summer was about $85. Dr Strangelove was able to do a version for around $50 recently.
I think if you want a dirt cheap relative measuring device that just gives you a number then buy a $1.50 allego 1302 Hall sensor and a $1.99 Harbor Freight Digital volt meter, 3 AA cells and a battery box. That will give you a reading for under $10. (+$3 shipping).

[Folkcafe]

Thanks David

A sensible argument for a calibrated meter. I can eventually muster up enough cash to purchase one, but one issue I have is determining which meter to get.

I suspect I might have had just too many questions in my post.

One question was regarding the Gauss meters from F.W. Bell specifically the 620. These seem readily available used and within an attractive price range. If not the 620 I think another important question would be "which meters should I be looking at that are affordable?"

Funny you should suggest the hall effect sensor. I did order 4 Allegro A1323 sensors this morning. The sensor I really wanted to order was the A1360. This one is a 4 lead programmable unit. The advantage is that you can set it to .7mv per G. This gives it a much more expanded range. 2.5v/.0007v = 3571 Gauss the A1323 I ordered is 2.5mv per G which is 1000G

I am fairly handy with electronics (Mass lic. master tech). I was in the consumer electronics service business for a number of years and still have a fairly well equipped tech bench. Yesterday I was going through some of it to see what I could sell off on Ebay and Craigslist to fund a Gauss meter. I have bench & handheld meters, freq counters, FM test generators, audio generators and lots more. I have this (enclosed picture) Leader laser power meter that might make a perfect donor chassis for a home built Gauss meter in the meantime. It works on a similar idea as a Gauss meter except it has a sensor tuned to laser light energy. The meter is self powered and simple. It would be fairly easy to adapt for use with a hall effect sensor.

I'm going to leave the question about the Bell 620 open on this thread for now. If I get no traction on it here, I'll post it as a separate question.

The fundamental question I probably should be asking is what measurement range should I be looking at and in the case of say the 620, what style measurement probe?

[David King]

Elepro's meter is good to about 1650 G with the 1302 probe but a differently equipped probe will get you well over 20,000 G -it's a extra few bucks if you need to measure neos. The second generation Gauss meter will become available I imagine as soon as enough interest has coalesced. If you can wait that long you'll be assured of a really fun project that is also state of the art for around 1/4 what you'd spend on a commercial device with fewer features. I'm sure a slew of the first gen meters will come up for sale when we all build the next one.

[Folkcafe]

Here is what I came up with

I dug through my old test gear and found a few mechanical tension gauges. This one is marked from 0-100 grams. For the tele bridge pickup in the picture, it gives at least a course measurement. Once I figure out what to get for an affordable Gauss meter, I'll one up.

[tonedeciple]

Cheapo Gauss Meter

I threw together one of these:

Build your own Gaussmeter

The only difference is I used an A1302 sensor. Next, I charged an alnico 5 bar in my drill press vice, which has two 3"x.5"x.5" N42s on each jaw. Then, I set the center of the north pole side against the A1302, plugged the DCV reading into the formula 1000*(VO-V1)/k. The result was 846 gauss.

I realize this number isn't as accurate as Elepro's meter, but it is at least a starting point. Next, I plan to charge and degauss several more A5s and try them out in a test mule humbucker pickup. That way I can associate a number with the tone I like. Not to shabby for a gauss meter that cost less than $15!