Permanent magnet question

L

lerameur

Guest
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
 
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...
Click to expand...
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 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, ?
Click to expand...
it's possible but there's no rule that favours either pole.

it could also be my gaussmeter...
Click to expand...
most likely.

build (or find) a solenoid (eg take the secondary winding
of a dead wall-wart transformer) and measure the gauss it
produces with the same known current flowing through it
in either direction.

Be aware that the earths magnetic field has a vertical
component in most locations.

Bye.
Jasen
 
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 .
Click to expand...

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
 
On Jul 23, 5:43 pm, John Popelish <jpopel...@rica.net> wrote:
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
Click to expand...
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
 
On Jul 25, 10:35 am, John Popelish <jpopel...@rica.net> wrote:
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
Click to expand...
What is an air gap inductor?
 
lerameur wrote:

What is an air gap inductor?
Click to expand...
Any magnetic structure that concentrates the magnetic flux
of a coil into an air gap.

You place the flux probe in the air gap. The presence of
the air gap tends to reduce lots of any nonlinearity
(between instantaneous current and instantaneous flux)
caused by the magnetic properties of the core material in
the rest of the flux path, while using that core material to
reduce the amperes it takes to reach a given flux level
(that is below the saturation flux of the core material).

A pair of E cores with a gap between the middle pair of legs
and a coil bedside that gap on each middle leg would be an
example of such a structure. Another would be a toroidal
core with a slot cut in it (to make an air gap). But even
placing the probe between a pair of solenoidal coils wound
around straight bars of permeable material would produce a
significant increase in flux, compared to air core coils,
especially if the cores extend out the ends of the coils by
at least the coil length. A pair of bundles of iron welding
rods (or cut pieces of coat hangers or floral wire) could
form such cores.

--
Regards,

John Popelish
 
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