maa@mullian.ee.mu.OZ.AU (Marc Alexander) (03/26/91)
If anybody knows how a Solid State/Electronic Compass works,(no moving parts.), would you mind telling me? I am interested in how it determines Magnetic North using electrical methods. Thanks for your help in advance, Marc Alexander |Internet maa@mullian.ee.mu.oz.au dept. of ee eng ,uni of melbourne |UUnet uunet!munnari!mullian!maa parkville 3052 australia gsxr1100jcr125rcex500rx2dod144 fax +61 3 344 6678 voice 3447689 "Interesting Concept!"
whit@milton.u.washington.edu (John Whitmore) (03/27/91)
In article <7167@munnari.oz.au> maa@mullian.ee.mu.OZ.AU (Marc Alexander) writes: >If anybody knows how a Solid State/Electronic Compass works,(no moving >parts.), would you mind telling me? >I am interested in how it determines Magnetic North using electrical >methods. A magnetized piece of iron has lower magnetizability (lower permeability) than an unmagnetized piece. So, if you examine the inductance of coils placed around, for instance, an iron ring, the permeability of the ring can be measured (I think this is actually done by examining the coupling of adjacent coils, i.e. it is actually a MUTUAL inductance measured, rather than an absolute inductance). The iron ring, if placed in the Earth's magnetic field, will magnetize its EAST and WEST edges because those parts of the ring are aligned with the field direction. Some magnetization in the North and South sectors will occur, but not nearly as much (this is a simple geometry effect). So the inductance measurement will show the orientation of the ring in the Earth's field. To get the absolute direction, one looks at some phase lead/lag characteristics; this is easily done, and depends on the magnetic field's polarity. It is not unusual to have a 'compass repeater' which puts the readout of the compass into some convenient place, and (at least some of these) have very high-order correction mechanisms (two dozen screw adjustments) so that a full 'pointing' of the ships' compass takes into account the changing magnetization of ALL the metal parts of the ship. On a sailing boat, the best place for the flux-gate is atop the mast (so it's far from the troublesome masses of iron). John Whitmore