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Gaussmeter


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2/1/2006 2:50 PM
Spence
Gaussmeter
Been looking for something a little more portable for measuring Gauss. Have a look at this device....  
 
http://www.carlsenmelton.com/gm200a/gm200a.htm  
 
These guys swear it's just the job for varying grades of AlNiCo and it seems quite a good price to me.  
 
Maybe someone knows of something better and cheaper. I kinda liked the idea of not having to attach a probe; something you could just put in your pocket.
 
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2/1/2006 7:18 PM
Dave Stephens
Spence this thing looks cheesy and there's no specs for it :-( I have the Alpha Labs gaussmeter it has a hall sensor on a ribbon wire and you can measure magnets under strings in guitar with it, it will measure the absolute strongest magnets in the world and the weakest. Its also $380, before you choke I did a quick search and found virtually the same one for $260, they are out of stock on it, but if you can get one of these they are the best:  
 
http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=detail&catalogno=4100
 
2/2/2006 6:48 AM
Spence

I asked them for some specs on this unit. I only really need it for a quick test when out of the workshop. The guys there told me....  
 
"You will be able to evaluate AlNiCo magnets with MMPA classes A1  
through A8 with our gaussmeter. The field strength you measure will, of  
course, depend on the shape of the magnet and its "internal residual field".  
For example, an Alnico 5 typically has an internal residual field of 12,800  
Gauss. A disc shaped magnet of this material would then exhibit  
approximately 6000 gauss externally at its face. The GM-200A has a range of  
0 to 10,000 gauss and would easily measure this field."  
 
I guess it'll do and I needed one quick for a big magazine article I'm taking part in in February. Just a bit of fun.  
 
BTW, I guess everyone's seen the article on building your own gaussmeter? What's the deal with Radio Shack? It's been a while, well years, since I was last in the States so looking for that hall effect device on the web was futile. Do they still sell components?
 
2/2/2006 12:15 PM
Jimi
Are you in the UK Spence? I was looking for that allegro chip aswell. Farnell sells a honeywell chip that looks like it would do the job. 5mv per gauss, + - 500 gauss. Whats the maximum gauss needed to measure pickups?
 
2/2/2006 3:42 PM
Spence

Yup, I'm in the UK and I've given up on that Allegro hall effect. I didn't try Farnell because I tried every other company thinking they'd have some idea of their competitor's components. They didn't. Radio Spares tried a bit harder than the rest. +/-10,000 gauss should cover AlNiCo from A1 to A8.  
The good thing about that unit I mentioned, although perhaps a little cheesy looking, was able to find the point of maxium gauss by scanning the whole surface of the magnet. It's a compact unit too which is ideal if you need to carry one around. Some of the hand-held device's I have seen weigh in at $600 or more.
 
2/2/2006 8:04 PM
Dave Stephens
Spence what the manufacturer told you is basically bull. In my experience using the Alpha Lab guassmeter, magnets from the same batch won't all magnetize equally, you'll get some that won't charge up as fully as one in the same shipment. Using a gaussmeter of any kind to determine which alnico grade a magnet it just doesn't work. Alnico deguasses itself over time, so you can't tell how much charge its lost. On top of that, vintage alnicos are even harder to figure out by guass because the mix of metals probably wasn't as precise and there's that issue of was it cast in a magnetic field or not which for sure changes how much charge A5 will take. The only cheap way to determine what grade of alnico is and is not entirely reliable, is by putting identical size alnco magnets in a test coil and doing inductance readings on it, this will get you real close.  
 
 
 
A good gaussmeter is an invaluable tool though, so their meter would probably be helpful but forget using it determine which alnico is which. Doesn't work
 
2/3/2006 1:14 PM
Spence

Dave, I can't take the magnets out of the pickups for the Strat shootout I'm taking part in so I kinda have to generalize. Essentially, I'm just going to give an idea of these magnets for the readers. Otherwize I will be doing all the usual inductance and DCr measurements.  
Judging by the relatively slow rate at which AlNiCo loses it's magnetism, I suspect some of it was probably never fully charged to start with.
 

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