Hobby Electronics Basics Permanent magnet question

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Subject Author Date
Permanent magnet question lerameur 07-23-08
Posted by lerameur on July 23, 2008, 4:03 pm
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Hello,

I have a permanent magnet and I just finish building myself a
gaussmeter. However it shows me that every magnet I measure has a
higher gauss level for the south then the north. Do magnet have
different magnetic field strength for south and north pole, ?
it could also be my gaussmeter...

k

Posted by John Popelish on July 23, 2008, 5:43 pm
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lerameur wrote:
> Hello,
>
> I have a permanent magnet and I just finish building myself a
> gaussmeter. However it shows me that every magnet I measure has a
> higher gauss level for the south then the north. Do magnet have
> different magnetic field strength for south and north pole, ?
> it could also be my gaussmeter...

Your gauss meter is not symmetrical through zero gauss, I
suspect. Try measuring a single pole with the the probe
turned each way, to see its asymmetry.

--
Regards,

John Popelish

Posted by lerameur on July 25, 2008, 9:43 am
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> lerameur wrote:
> > Hello,
>
> > I have a permanent magnet and I just finish building myself a
> > gaussmeter. However it shows me that every magnet I measure has a
> > higher gauss level for the south then the north. Do magnet have
> > different magnetic field strength for south and north pole, ?
> > it could also be my gaussmeter...
>
> Your gauss meter is not symmetrical through zero gauss, I
> suspect. Try measuring a single pole with the the probe
> turned each way, to see its asymmetry.
>
> --
> Regards,
>
> John Popelish

I calibrated at zero gauss. So when there is no magnetic field present
I took this value as zero Gauss, then I use 1000 gauss as the highest
value for 4.8v using the linear formula y=mx+b .

Ken

Posted by John Popelish on July 25, 2008, 10:35 am
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lerameur wrote:

> I calibrated at zero gauss. So when there is no magnetic field present
> I took this value as zero Gauss, then I use 1000 gauss as the highest
> value for 4.8v using the linear formula y=mx+b .


Have you checked the linearity? I think I would try to
compare the signal to a current that produced the magnetic
field with a gapped inductor, with the probe in the gap, and
the inductor fed with AC. A scope Lissajous pattern would
display the linearity very simply.
http://en.wikipedia.org/wiki/Lissajous_curve

--
Regards,

John Popelish

Posted by lerameur on July 25, 2008, 12:10 pm
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> lerameur wrote:
> > I calibrated at zero gauss. So when there is no magnetic field present
> > I took this value as zero Gauss, then I use 1000 gauss as the highest
> > value for 4.8v using the linear formula y=mx+b .
>
> Have you checked the linearity? I think I would try to
> compare the signal to a current that produced the magnetic
> field with a gapped inductor, with the probe in the gap, and
> the inductor fed with AC. A scope Lissajous pattern would
> display the linearity very simply.http://en.wikipedia.org/wiki/Lissajous_curve
>
> --
> Regards,
>
> John Popelish

What is an air gap inductor?


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