Gauss meters, any reviews?

Anyone know much about gauss meters?
Just wanting to measure strengths of permanent magnets for projects ranging from massive subwoofer builds to robotics? Neo, Ferrite magnets what ever.
Not to expensive maybe under $400 or $500 obviously cheaper the better like it doesn’t have to spot on accuracy but a reasonable one would be good!!

Any recommendations?
Cheers
 

Dave Zan

Member
2010-11-21 7:12 am
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1audio

Member
Paid Member
2004-03-24 5:16 am
SF Bay Area
Thanks Guys so much!!!
Yes, it is to measure voice coil gaps and a lot of other things too like the strengths of neodymium and ferrite magnets and various other things as my hobby is making things, modifying thing, designing things…. I’m always learning!! The smaller the sensor the better as I don’t know how small they come as I dare say in the future I would want to measure something like the strength of the gap of a 1inch coil if possible which is quite small/thin.

**And a side note is that some of the magnets will be very strong like 20kg/40lb magnets so I don’t know what numbers they will put out therefore I need a tool that can easily give me a reading from such large magnets. I don’t want to exceed the capabilities of the meter :O

I did see a guy use an Alpha labs gm-2 to measure a gap of a massive subwoofer, I like that meter but it’s expensive I was hoping for something cheaper as I don’t need anything top quality but something reasonable.
@ Dave Zan I will definitely keep that in mind (I’ve saved that PDF) thankyou, I’d rather just buy a meter as if I make one that would only be another project to add to the many I’m currently working on…. I don’t need any more projects until I finish the ones I’m working on now haha
 
Hi,


I´m just in front of the same decision, what to buy? The Bell mentioned by Demian is most probably a good choice, but seeing the ad for one tenth of the new price makes me a bit suspicious...
The chinese machines like
TD8620 Permanent Magnet Gauss Meter Handheld Digital Tesla Meter Magnetic Flux Meter Surface Magnetic Field Test 5% Accuracy on AliExpress
are cheap and are available everywhere. In Europe, the Voltcraft GM 70 is available for around 250 € and seems to be a step more serious than the chinese clones of whatever.
Does anybody has any experience with these machines?



Many thanks in advance and best regards


Mattes
 

Dave Zan

Member
2010-11-21 7:12 am
so I don’t know what numbers they will put out therefore I need a tool that...I don’t want to exceed the capabilities of the meter :O

As the magnet becomes more massive the flux increases but the field stays much the same, like more amps but same volts.
So ~2 T is about all you will need for iron and permanent magnets, 2.4 T is the limit for the meter linked below and that should be fine.


That looks pretty decent, the basic principle is a Hall effect sensor and ADC so it should be essentially a commodity item.
They make the effort to publish a few specifications and the numbers and price look believable.
Also it's easy to check the calibration and linearity with a simple homemade Helmholtz coil (or Maxwell coil if you are fussy) so it seems like a sensible buy.

Best wishes
David
 
Thanks,
Nice I'll check that link out.
I was thinking of the f.w. Bell 4048 is that a good idea???? because I can get one for about $200 but then I’m very worried if it will be ok being secondhanded will it work haha seems very cheap? Do they need calibrating??
The 4048 specifications state: Full scale ranges 200G,2kG, 20kG, 20mT, 2T
So I’m guessing it will do the range I’m after because that subwoofer that guy measured was about 7000gauss I assuming it’s gauss as there’s an arrow pointing to gauss on the meter.
So the F.W. Bell 4080 will do 20,000Gauss 2T=20,000 Gauss right?
Cheers guys.

p.s. that link you showed us is real tempting!!! is it a single axis? like is it facing the right way for a voice coil gap reading?
 

Dave Zan

Member
2010-11-21 7:12 am
Your conversion is correct, so the subwoofer is 0.7 T, which is a realistic, typical number, much more than 1T is unusual, there's a few pro woofers around 1.2 T IIRC
Pro compression drivers are up to around 2 T, disproportionately expensive past that, a few "boutique audiophile" around 2.2 T and that's about the practical limit.

The Chinese unit seems to have the correct orientation for VC test as standard.

Best wishes
David
 
Just as a side comment, the Hall sensor you show is 3 mm wide by 0.8mm thick.

Thickness is apparently fine, since narrow gaps can go down to 1.1mm and maybe 1 mm in an exceptional speaker, but gaps are circular, not sure how well a 3 x 0.8mm *rectangle* can fit in.

Too sleepy now to do some geometrical forecasting but guessing it will be a very tight fit into some small diameter gaps.

Think 1" voice coils and such.
 

Dave Zan

Member
2010-11-21 7:12 am
Just as a side comment, the Hall sensor you show is 3 mm wide by 0.8mm thick.
...
Think 1" voice coils and such.

Real audiophiles only have woofers and compression drivers with 4" VC;)
Maybe 3" on the compression driver...
I think the 3 mm width is not too much of a problem even on a 25 mm VC, if my own sleepy calculations are correct, adds another 0.1 mm or so.
Probably possible to very carefully sand just the corners to trim that fraction of a millimetre.

many thanks for your helpful comments on the chinese TD8620, much appreciated.

A pleasure, if you do buy one then tell us how it works out.
That Voltcraft GM70 looks like a Chinese machine made to order for the European market.
Probably a Euro supplier would write better instructions and support the product themselves, worth it?

Best wishes
David
 
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ghemml

Member
2010-09-19 5:18 am
TD8620 Permanent Magnet Gauss Meter Handheld Digital Tesla Meter Magnetic Flux Meter Surface Magnetic Field Test 5% Accuracy-in Electromagnetic Radiation Detectors from Tools on AliExpress

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Hi,

the shown Chinese meters seems to be just right for speaker measurements?
No, the caveat are the probes that come with them. These probes are usually on 1,6mm thick PCB material, being 5mm wide. One of the suppliers gave these measures with the 8620 model. This is too wide to be used in magnetic gaps of most speakers.

The previously mentioned 0,8mm would be a bit better, but excluding too many speakers.

Now, this is DIYaudio, so who dares to buy a sub$100 one and file or 'dremel' the PCB down to the copper traces leaving just a hair of PCB...?

A Teslameter dedicated for speaker gap measurement costs around $350 to 500. Included is a probe which has the sensor on some Kapton or similar plastic. Just 0,6mm thick and slightly flexible. Vatmag is the brand.
This is small enough to fit most speakers.



FWIW
Thomas