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Mag forum,
Another angle:
Am late on this discussion as I have been maggin in Mocambique
and have returned without malaria, cholera or yellow fever.
I have wound a number of coils mostly solenoids and found a
simple test for magnetic buildup which may be useful, as follows:
In the field, a magnetized solenoid will show a deviation if swung
from E-W to W-E, at worst up to 5 nT . Couldnt find any effect
of ferrous contaminated Cu wire and assumed it would cancel
itself out within the wire**. Did get deviations when mag probes
were rubbing against anchor chain in the bilges of the boat or
dragged across a warehouse floor or deck of a steel survey vessel.
The test system I used was a hollow solenoid into which a bottle
could be placed for testing the various fluids and over which a
PVC housing with various plastics could be tested . Ran it
overnight at 2 A from 24v DC to get some serious polarization and
tested it in the field on top of a 3 Metre wooden pole which could
be rotated and the trace observed. Using a notebook and a
PICOSCOPE oscilloscope a number of measurements of various
type s could be obtained
. After that one can use the least offensive of the various
materials from the same stocks to build the final toroid etc.
I like the idea of bifilar windings but always think of the field
situation like what cable to use and where the earth will be .
Cable is always a problem and stray voltages on a boat can realy
become a character -building experience. In addition ,cables can
be microphonic and change capacitance (pF) with wave action ...
George
**PS Quiz: a ferrous particle in the very centre of a current
carrying copper wire will become polarized in which direction?
Another angle:
Am late on this discussion as I have been maggin in Mocambique
and have returned without malaria, cholera or yellow fever.
I have wound a number of coils mostly solenoids and found a
simple test for magnetic buildup which may be useful, as follows:
In the field, a magnetized solenoid will show a deviation if swung
from E-W to W-E, at worst up to 5 nT . Couldnt find any effect
of ferrous contaminated Cu wire and assumed it would cancel
itself out within the wire**. Did get deviations when mag probes
were rubbing against anchor chain in the bilges of the boat or
dragged across a warehouse floor or deck of a steel survey vessel.
The test system I used was a hollow solenoid into which a bottle
could be placed for testing the various fluids and over which a
PVC housing with various plastics could be tested . Ran it
overnight at 2 A from 24v DC to get some serious polarization and
tested it in the field on top of a 3 Metre wooden pole which could
be rotated and the trace observed. Using a notebook and a
PICOSCOPE oscilloscope a number of measurements of various
type s could be obtained
. After that one can use the least offensive of the various
materials from the same stocks to build the final toroid etc.
I like the idea of bifilar windings but always think of the field
situation like what cable to use and where the earth will be .
Cable is always a problem and stray voltages on a boat can realy
become a character -building experience. In addition ,cables can
be microphonic and change capacitance (pF) with wave action ...
George
**PS Quiz: a ferrous particle in the very centre of a current
carrying copper wire will become polarized in which direction?