Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-09-28
2001-01-30
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207240, C073S861740
Reexamination Certificate
active
06181128
ABSTRACT:
TECHNICAL FIELD
This invention relates to magnetic sensors, and more particularly to a magnetic sensor for measuring a physical property that can be translated into the flexing of a beam.
BACKGROUND OF THE INVENTION
It is known in the art relating to sensors to provide a sensor that can convert small distances traveled by a body across the sensor into a proportional electrical signal. One possible application for such a sensor is a flowmeter. Such sensors could be used in automotive applications to sense liquid or gas flow, e.g. air mass flow within an automotive fuel system to determine the flow rate of intake air to an engine.
In the past, flow sensors have often been in the form of hot wire devices, pressure sensing devices and turbine devices. Such sensors can be complicated in construction, relatively expensive, require complicated electronic circuits for developing linear output signals and many of them are incapable of determining flow direction.
SUMMARY OF THE INVENTION
The present invention provides a simple, very sensitive and low cost magnetic sensor suitable for a variety of applications where a physical property can be translated into the flexing of a beam. The sensor includes a support which extends outward from a base to a distal portion. A beam is fixed to the distal portion and extends inward therefrom to a free end of the beam adjacent the base.
A pair of matched magnetic sensing elements are mounted on the base adjacent and opposing the free end of the beam which is nominally centered between the sensing elements. A magnetic field means is disposed against the magnetic sensing elements and at the free end of the beam. Magnetic field means may be provided by a biasing magnet coupled with a high permeability material.
The free end of the beam is resiliently connected with the base through the beam and the support whereby force applied against the beam may move the free end closer to one and further from the other of the sensing elements. A differential signal is generated between the sensing elements by connecting a driving means to the sensing elements. The differential signal indicates the various positions of the free end of the beam for conversion to operational data.
In preferred embodiments, the sensing elements are magnetoresistors made from indium antimonide. When a force is applied to the beam, the beam moves closer to one magnetoresistor and the resistance in that magnetoresistor increases while the resistance in the other decreases. The voltage outputs across each magnetoresistor follow a similar pattern as the resistance of each magnetoresistor. A differential signal between the voltage outputs across the magnetoresistors and the distance traveled by the beam will have a linear relationship within known dimensional limits. The linear output can be used to determine various characteristics of the force applied to the beam.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
REFERENCES:
patent: 3971253 (1976-07-01), Hini et al.
patent: 4625565 (1986-12-01), Wada et al.
patent: 5767419 (1998-06-01), Hutchinson
Siemens Magnetic Sensors Data Book, “Differential Magnetoresistive Sensor”, 1989, pp. 107, 110.
Dobrowitsky Margaret A.
General Motors Corporation
Patidar Jay
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