Measuring magnets gauss

[AlvaroHN]

What do you people use to measure the magnets gauss???

I am building a new ssg,

and yesterday I got the magnets,

I am going to put them stacked in pairs.

I need 20 and I bought 40, to match the 20 with less difference in gauss.

I am using my android phone magnetometer... but it seems that the magnets saturate the phone sensor and after the 5ft magnet the magnetometer reading change, and I can't measure them all properly.

Does anybody have a lifesaving solution which does not include buying an expensive gauss meter?

best,

Alvaro Hernandorena

[RS_]

http://www.thebackshed.com/windmill/...GaussMeter.asp


here is a better site and where my gauss meter circuit came from
http://www.coolmagnetman.com/magmeter.htm
http://www.coolmagnetman.com/magmetr1.htm

[AlvaroHN]

Tnx RS you are always very kind.

I found some hall devices in a cd-rom reader, in the motor part.

They have 4 pins and not 3, do you know if this type of hall is useful to the gauss meter?

And I see in the circuits on the links that they use a 9v battery and a voltage regulator. .. can I just use a cellphone charger rated in 5v directly to the hall?

Best

Alvaro

[RS_]

No, that hall will prob. not work..... it is most likely a on/off output only.... check its part # to see

you want a linear output hall effect sensor...A1302KUA-T or A3516LUA
http://www.allegromicro.com/Products...ensor-ICs.aspx
http://www.allegromicro.com/en/Produ...s/A1301-2.aspx

and so long as the 5V is stable, it should work.... but you will still need a higher +/-supply voltage's for the op amp circuit to run from

LM741 opamps will work too

allegro is good about sending free samples....

[RS_]

the gauss meter opamp circuit will also work with these hall effect current sensors and make nice instrumentation for your experiments
http://www.amploc.com/amploc.com/AMPLOC.html

Use a volt meter like this one for the opamp output on the gauss meter and the current meter projects
Red 4-1/2 Digit LED DC 20V Digital Volt Meter Power 5V
http://www.ebay.com/itm/Red-4-1-2-Di...item51974afac2

EDIT
You also want to look at the Gauss and Current sensors output wave forms on a Oscope...... very interesting when comparing the wave forms to the voltage over the coil wave form........

[AlvaroHN]

I contacted live chat on digikey to ask for free samples of allegro linear hall sensor,... and they almost sent them... until I said I was not a company, so I would have to order some online and wait them to arrive...

I can buy them here in Uruguay, but they are too much expensive vs internet price, .. on ebay I get 10 for US$ 4,8.. here I get 1 for US$ 10.

best,

Alvaro

[AlvaroHN]

Update on this subject: having magnets with exactly the same strength is very hard! !!

Last week I received alegro hall sensors that I bought and made a simple circuit with the voltmeter the hall and a 5v source. And finally I was able to measure the magnets.

I made interminable combinations of pairs until I got 10 pairs of magnets all with same strength.

Then I installed those magnets on my rotor and repeated the hall measurement but with magnets in the rotor this time.

I got some differences because not all magnets slots on the rotor where perfect. So again I corrected that untill I got same reading from all magnets.

But! The amp meter didn't show the pulse swift at the exact same time when speeding up.

What are your experiences with this guys?

Do you get the pulse swifts at the same time on all magnets?

I find this issue very important and haven't find much info about it.

Best

Alvaro