General Electric Company

Jish M Wang

Ami E Berkowitz

Joseph A Lahut

Matthew N O'Donnell

William A Edelstein

William D Barber

Steven G Karr

Richard O McCary

A method for minimizing the inhomogeneity of a static magnetic field, produced by a main magnet, over a selected arbitrary volume, by operation of a plurality N of shimming coils each independently producing an associated shimming magnetic field having an associated inhomogeneity which is a function of spatial location over that same volume, uses the steps of: measuring the magnitude of the main magnet field, in the absence of all shimming fields, at a plurality of locations X.sub.i upon the surface of an imaginary sphere enclosing the arbitrary volume; measuring the polarity and magnitude of each of the N shimming fields, with respect to the polarity and magnitude of a D.C. current flowing through the associated shimming coil, at the same plurality of locations X.sub.i upon the imaginary sphere surface; determining the weighted mean-square variation of the total field at each of another plurality of points Y.sub.i within the volume of said imaginary sphere; and (d) selecting the current magnitudes and polarities for each of the N shimming coils to provide each of the N associated shimming fields with magnitude and polarity to minimize the inhomogeneity of the main magnetic field in the arbitrary volume. The set of weighting coefficients may be selected to all be equal, or to emphasize at least one desired region of the arbitrary volume.

Method for homogenizing a static magnetic field over an arbitrary volume

A conductive multilevel liquid sensor uses conventional integrated circuits such as inverters and voltage comparators as signal detectors, and a flat cable having corrosion-resistant probe conductors of different lengths as the sensing probe assembly. The binary encoded outputs of the signal detectors identify the sensed liquid level. A continuous level control is realized by the addition of timing logic, and sensor operation range is improved by having the voltage at one comparator input be adaptive to the change in liquid conductivity.

Multilevel liquid sensing system

An easily assembled transverse magnetic printing head and method for making same are disclosed for use in a coincident current, matrix-driven, transverse printing head. In accordance with one embodiment of the present invention, digit lines pass through a recording gap in mirror image fashion as between adjacent word groupings. Similarly, the word line patterns are arranged on a printed circuit board in a zig-zag fashion. A feature common to both the word and digit line printed circuits, however, is the presence of a small expanse of circuit wiring unsupported by printed circuit substrate material through which a high permeability magnetic comb structure is inserted to form required recording gaps. The coincident current scheme is retained by driving the digit lines from alternating directions. The arrangement of the digit lines in the present invention permits the use of a planar printed circuit with no crossovers and therefore a circuit which is easily fabricated in a flexible, printed circuit design.

Easily assembled transverse magnetic printing head

In order to achieve higher resolution in printed data, separate magnetic printing head sub-assemblies are adjacently disposed with respect to each other. Each sub-assembly includes a high permeability magnetic comb structure with teeth protruding through elongated slots in a pair of flexible printed circuit boards. High resolution is achieved by a relative offset of the comb teeth so that the teeth of the comb in the second sub-assembly align with the gaps in between the comb teeth in the first sub-assembly.

High resolution magnetic printing head

The signal-to-noise ratio as measured by the ratio of the full select magnetic field levels to the half select magnetic field levels, is improved in a coincident current magnetic printing head by providing means for producing a bias magnetic field which is at least somewhat opposed to the signal magnetic fields.

Magnetic printing head having a high signal-to-noise ratio

A magnetic printing head, for selectively magnetizing regions of magnetic recording media moving transversely therepast, has an elongated comb-like member of magnetizable material. Each of a multiplicity of slots in the member contains conductor means energizable to carry a flow of current for generating a magnetic orientation field between two adjacent comb-tooth tips and transverse to the direction of media movement. The conductor means in each slot may comprise at least a pair of independently energizable conductors for generating the orientation field responsive to coincident flows of current therein, preferably selected by matrix techniques.

Growing community of inventors

Schenectady, NY, United States of America

Jish M Wang