Appeal No. 1997-2245 Page 13
Application No. 08/402,872
strength will have an equivalent strength when read by either
sensor. However, the magnet's magnetic field strength will
not have equivalent values when read by the sensors because of
the different distance between each sensor and the magnet
(col. 6, line 42-58). Thus, the distance between the sensors
provides a gradient between the magnet's magnetic field sensed
by the spaced apart sensors, while at the same time nulling
the sensing of the ambient magnetic field. To ensure that the
signal sensed represents the magnet in the patient, the magnet
is manipulated i.e., by turning the tube, until the polarity
changes.
From these teachings of Golden, we find that Golden does
not use the flux-gate sensors as part of a compass. In our
view , in order for a flux-gate sensor to form a compass, a5
second set of output excitation windings would need to be
provided in quadrature with the first set of output windings,
with one output winding set to represent north/south and the
second set of output windings set to represent east/west with
accompanying circuitry for operation as a flux-gate compass.
5See U.S. Patent 5,090,231 entitled "Electronic Compass System" col. 1,
lines 18-61.
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