From what i've read, it sounds like the permeability
of a conductive enclosure will increase the density
of the lines of magnetic flux within the conductor,
so that the magnetic field within the enclosure
will be less intense, which in effect can make
the compass less accurate (or slower to respond).

I'll be using a Honeywell digital compass, and
I need to know if the metal chassis will need
to have openings around the compass or not.

Or, i may need to use a plastic enclosure instead.

Both purely mathematical/theoretical and real-world
answers welcome.

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

From what i've read, it sounds like the permeability
of a conductive enclosure will increase the density
of the lines of magnetic flux within the conductor,
so that the magnetic field within the enclosure
will be less intense, which in effect can make
the compass less accurate (or slower to respond).

I'll be using a Honeywell digital compass, and
I need to know if the metal chassis will need
to have openings around the compass or not.

Or, i may need to use a plastic enclosure instead.

Both purely mathematical/theoretical and real-world
answers welcome.

On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field.  How much it affects the
the response depends on the details of the construction, of course.

On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field. How much it affects the
the response depends on the details of the construction, of course.

From what i've read, it sounds like the permeability
of a conductive enclosure will increase the density
of the lines of magnetic flux within the conductor,
which in effect can make....
the compass less accurate (or slower to respond).

A Faraday cage is for protection, and in that context you are correct. If the

Paul <Quiller...@gmail.com> wrote:
On Apr 4, 10:14?am, Benj <bjac...@iwaynet.net> wrote:
On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field. ?How much it affects the
the response depends on the details of the construction, of course.
� � � � �Are you saying that the magnetic field will not
be distorted due to a non-magnetic, but conducting cage?
� � � � �Both the compass and the cage will move within the
field.

Moving a conductor in a magnetic field will induce current, called
eddy currents, in the conductor, which in turn cause magnetic
fields.

The magnitude of those induced fields will be proportional to the
magnitude of the external field and the velocity of the conductor.

Unless the external magnetic field is a lot greater than the Earth's
and the conductor is moving really fast and is really close to the
compass, you are unlikely to see any effect.

However, accelerating or turning a compass will cause compass errors
all by itself. I'm assuming an ordinary mechanical compass here.

--
Jim Pennino

Remove .spam.sux to reply.- Hide quoted text -

- Show quoted text -

Paul <Quiller...@gmail.com> wrote:
On Apr 4, 4:25???pm, j...@specsol.spam.sux.com wrote:
Paul <Quiller...@gmail.com> wrote:
On Apr 4, 10:14?am, Benj <bjac...@iwaynet.net> wrote:
On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field. ?How much it affects the
the response depends on the details of the construction, of course..
??? ??? ??? ??? ???Are you saying that the magnetic field will not
be distorted due to a non-magnetic, but conducting cage?
??? ??? ??? ??? ???Both the compass and the cage will move within the
field.

Moving a conductor in a magnetic field will induce current, called
eddy currents, in the conductor, which in turn cause magnetic
fields.

The magnitude of those induced fields will be proportional to the
magnitude of the external field and the velocity of the conductor.

Unless the external magnetic field is a lot greater than the Earth's
and the conductor is moving really fast and is really close to the
compass, you are unlikely to see any effect.

However, accelerating or turning a compass will cause compass errors
all by itself. I'm assuming an ordinary mechanical compass here.

--
Jim Pennino

Remove .spam.sux to reply.- Hide quoted text -

- Show quoted text -
� � � This will be a digital compass, with MEMS
accelerometers.
� � � Are you saying that the magnetic field will
not be distorted due to a non-magnetic, but
conducting cage? �As if the cage wasn't there?

If the cage is not moving relative to the field, no distortion.

If otherwise, see above.

On Apr 4, 10:14?am, Benj <bjac...@iwaynet.net> wrote:
On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field. ?How much it affects the
the response depends on the details of the construction, of course.

Are you saying that the magnetic field will not
be distorted due to a non-magnetic, but conducting cage?

Both the compass and the cage will move within the
field.

On Apr 4, 4:25???pm, j...@specsol.spam.sux.com wrote:
Paul <Quiller...@gmail.com> wrote:
On Apr 4, 10:14?am, Benj <bjac...@iwaynet.net> wrote:
On Apr 3, 9:25 pm, j...@specsol.spam.sux.com wrote:

A non-magnetic cage around a compass will have no effect, conductivity
isn't the issue for static magnetic fields.

What Jim means it a conductive enclosure (provided it isn't TOO
conductive) won't effect the static readings of the compass. (a
superconducting enclosure would block magnetic fields) On the other
hand the conductive enclosure could affect the speed of response of
the compass due to eddy current effects as the magnetic field is
changed or the device moved in that field. ?How much it affects the
the response depends on the details of the construction, of course.
??? ??? ??? ??? ???Are you saying that the magnetic field will not
be distorted due to a non-magnetic, but conducting cage?
??? ??? ??? ??? ???Both the compass and the cage will move within the
field.

Moving a conductor in a magnetic field will induce current, called
eddy currents, in the conductor, which in turn cause magnetic
fields.

The magnitude of those induced fields will be proportional to the
magnitude of the external field and the velocity of the conductor.

Unless the external magnetic field is a lot greater than the Earth's
and the conductor is moving really fast and is really close to the
compass, you are unlikely to see any effect.

However, accelerating or turning a compass will cause compass errors
all by itself. I'm assuming an ordinary mechanical compass here.

--
Jim Pennino

Remove .spam.sux to reply.- Hide quoted text -

- Show quoted text -

This will be a digital compass, with MEMS
accelerometers.

Are you saying that the magnetic field will
not be distorted due to a non-magnetic, but
conducting cage? As if the cage wasn't there?

Paul <Quiller...@gmail.com> wrote:
Unfortunately, the cage is this case will
be a conducting chassis, which will enclose the
digital compass. This will be a portable device,
which the user will walk around with.
It won't be a super-conducting shell,
so the eddy currents will dissipate as heat. Hopefully
the effect will be somewhat transient, but the fact
that the compass itself is sensitive enough to
measure the earth's magnetic field, means that
it just may be sensitive enough to pick up distortions
to the field due to the motions of the user, even
if those motions are relatively slow.

A simple test would be to put the compass with and without the cage
on a turntable and spin it; note any difference.

--
Jim Pennino

Remove .spam.sux to reply.

Unfortunately, the cage is this case will
be a conducting chassis, which will enclose the
digital compass. This will be a portable device,
which the user will walk around with.

It won't be a super-conducting shell,
so the eddy currents will dissipate as heat. Hopefully
the effect will be somewhat transient, but the fact
that the compass itself is sensitive enough to
measure the earth's magnetic field, means that
it just may be sensitive enough to pick up distortions
to the field due to the motions of the user, even
if those motions are relatively slow.