Position sensor

Details Position sensor Position sensor

1992-07-20

1994-02-01

Cuchlinski, Jr., William A.

Geometrical instruments

Indicator of direction of force traversing natural media

Magnetic field responsive

33346, 33361, 33363R, G01C 2108, G01C 1730

Patent

active

052823180

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

A position sensor is disclosed in German Auslegeschrift 1,773,303. In this known apparatus, a core is surrounded by an exciting coil, which is coiled uniformly about the core and which is energized by a periodic voltage or a periodic current, so that the core is driven far enough into the saturation range. Four receiving coils are disposed over the circumference, offset in each case by 90.degree., the diametrically opposed receiving coils being connected back-to-back. By forming the difference between the voltages induced in the pairs of receiving coils, the transformed voltage basically is cancelled in these coils. However, an external magnetic field, particularly the horizontal component of the earth's magnetic field, brings about a shift in the operating point on the characteristic magnetization curve, which results in a phase shift that causes a non-cancelling voltage portion. This consists essentially of harmonics of an even order of the exciting frequency, the amplitudes of which are proportional to the external magnetic field. In the evaluating circuit, which is connected with the receiving coil, the second harmonic advisably is evaluated in order to generate a signal which corresponds to the direction of the external magnetic field. As a result of the inhomogeneities and asymmetries in the core and in the coils, this apparatus is not suitable for more accurate measurements. Moreover, it has a plurality of components and is therefore quite expensive. Even in the case of a variation with an annular magnetic core floating in a hermetically sealed toroid, said toroid is supported on a quite expensive suspension device.
French publication 2,601,185 discloses a magnetic core for a compass, in which the receiver coils embrace the annular magnetic core diametrically and do not embrace the cross section of the annular magnetic core, as they do in the aforementioned German Auslegeschrift 1,773,303.
German Offenlegungsschrift 3,012,241 discloses a further apparatus for measuring a magnetic field. For this apparatus, a liquid-supported float is used, which can be pivoted on a bearing shaft lying in a horizontal plane. The bearing shaft rests in an orbiting guiding groove, so that the float can also carry out a rotational movement. A rigid assignment of the float to a particular orientation of the housing is thus not assured.


SUMMARY OF THE INVENTION

It is an object of the invention to provide an apparatus of the initially mentioned type, which relatively inexpensively provides a measurement of high reliability and accuracy. Briefly stated, in accordance with the invention, a position sensor is provided in which a ring of a material of high permeability is floated on a liquid within a toroid, so as to hold the ring in a horizontal position. Exciting coils are distributed uniformly about the ring to enclose the cross section thereof, and receiving coils are distributed uniformly about the circumference of the ring.
The invention is described in the following disclosure with examples and reference to the Figures. In the drawings:
FIG. 1 is a plan view of the apparatus for measuring the magnetic field,
FIG. 2 is a cross section through the apparatus of FIG. 1,
FIG. 2A is a cross sectional view, on a larger scale than FIG. 2, of an alternate embodiment in which the annular element 12 of FIG. 2 is surrounded by a sheath,
FIG. 3 is a diagrammatic representation of the linkage of the individual parts of the apparatus to one another.


DETAILED DISCLOSURE OF THE INVENTION

The toroid 10, is externally hermetically sealed towards the outside and shown in plan view in FIG. 1, and is disposed in binoculars (not shown), so that its principal plane is approximately horizontal. The interior of the toroid is partially filled with a rather low viscosity liquid 11, preferably corresponding to half the volume of the toroid. The low viscosity of the liquid ensures a high reaction speed and a low tendency to form bubbles. An annular element 12 of a highly permeable material, which may also be surrou

REFERENCES:
patent: 4546550 (1985-10-01), Marchent et al.

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