糖心TV

Professor Barry Narod University of British Columbia Magnetic permeability and domain structure, and their influence on fluxgate magnetometer noise Abstract: I will briefly review magnetotellurics as a field method, then review demand/capability of various induction magnetometers, including fluxgates. I will end by reviewing the principles of operation of fluxgate magnetometer sensors. I will go on to discuss three experiments we have performed which are designed to examine the relationships between particular magnetic material properties and fluxgate magnetometer noise. (i) The first experiment examines the relation in ring cores [toroids] between effective differential permeability and magnetometer noise. We find that there exists a strong inverse correlation. A classical derivation of differential permeability then leads to the conclusion that magnetometer noise reduces as does the number of active domain walls within the magnetic core. (ii)The second experiment considers the relation between the ring core cross section and effective differential permeability and/or magnetometer noise. We find that, although the thin ribbons which are the norm for ring cores can have very high permeability when compared with circular cross-section materials, they do not necessarily offer superior noise performance. Wires of circular cross-section magnetic materials can offer good noise performance and offer several advantages during ring core fabrication and processing. The effects of shape with respect to magnetic heat treating will be discussed. (iii) The third experiment separates the magnetometer noise effects of Barkhausen noise, and domain nucleation/denucleation, by suppressing Barkhausen noise. Our initial results imply that Barkhausen noise does not contribute significantly to fluxgate magnetometer noise. Domain nucleation/ denucleation appears to be the primary source for magnetometer noise. Thu, 30 Mar 2006