MEASUREMENT OF FLUID FLOW
First Claim
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1. Apparatus for sensing the rate of fluid flow through a conduit, comprising flow responsive means rotatably mounted within the conduit for transforming fluid motion into rotational motion;
- magnetic means mounted on said flow responsive means for producing a time varying magnetic field proportional to the rate of flow of the fluid;
input potential means for providing a source of electrical energy;
output signal circuit means for indicating the rate of flow of the fluid; and
field responsive means mounted adjacent said flow responsive means for providing electrical energy in the form of an output signal responsive to the time varying magnetic field by modulating the electrical energy from said input potential means, said field responsive means including at least one magnetoresistive element of semiconductor material, each said magnetoresistive element having a single input lead connected to said input potential means and a single output lead connected to said output signal circuit means to cause substantially all the energy supplied to said output signal circuit means by said field responsive means to be derived from said input potential means.
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Abstract
An electric signal is produced which is dependent on fluid flow, by producing a magnetic field which changes with fluid flow and by positioning in the changing magnetic field a semiconductor detector whose electrical characteristics change in accordance with the changes in the field and which produces the electric signal in response to those changes.
90 Citations
7 Claims
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1. Apparatus for sensing the rate of fluid flow through a conduit, comprising flow responsive means rotatably mounted within the conduit for transforming fluid motion into rotational motion;
- magnetic means mounted on said flow responsive means for producing a time varying magnetic field proportional to the rate of flow of the fluid;
input potential means for providing a source of electrical energy;
output signal circuit means for indicating the rate of flow of the fluid; and
field responsive means mounted adjacent said flow responsive means for providing electrical energy in the form of an output signal responsive to the time varying magnetic field by modulating the electrical energy from said input potential means, said field responsive means including at least one magnetoresistive element of semiconductor material, each said magnetoresistive element having a single input lead connected to said input potential means and a single output lead connected to said output signal circuit means to cause substantially all the energy supplied to said output signal circuit means by said field responsive means to be derived from said input potential means.
- magnetic means mounted on said flow responsive means for producing a time varying magnetic field proportional to the rate of flow of the fluid;
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2. Apparatus as claimed in claim 1 wherein said input potential means is a DC power source and said output signal circuit means includes a resistor connected in series with said field responsive means across said DC power source, said DC power source being connected to the input connection of each such magnetoresistive element and said resistor being connected to the output connection of each such magnetoresistive element, and trigger circuit means connected to provide a pulse output in response to resistance changes in said magnetoresistive element.
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3. Apparatus as claimed in claim 2 wherein said resistor is a second magnetoresistive element positionEd outside said magnetic field so as to be exposed to the same temperature conditions as the magnetoresistive element of said field responsive means.
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4. Apparatus as claimed in claim 1 wherein said field responsive means includes a resistive bridge circuit including a pair of magnetoresistive elements connected in opposed arms of said bridge circuit and positioned to respond successively to changes in said magnetic field, said output signal circuit means including trigger circuit means connected to receive an output signal from said bridge circuit, said trigger circuit means operating to provide a pulse output in response to said bridge circuit output signal.
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5. Apparatus as claimed in claim 1 wherein said input potential means is an AC power source and said output signal circuit means includes a resistor connected in series with said field responsive means across said AC power source, an amplifier connected across said resistor, and a demodulating and pulse shaping circuit means connected to receive an output signal from said amplifier.
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6. Apparatus as claimed in claim 1 wherein said flow responsive means includes a tangential flow turbine member mounted for rotation in a turbine casing through which fluid flows, said turbine member being mounted for rotation about an axis at right angles to the direction of fluid flow by an axially extending turbine shaft rotatable therewith, said magnetic means includes a disc connected to said turbine shaft for rotation therewith remote from said turbine member, said disc being magnetized in a direction transverse to the axis of rotation thereof, said field responsive means includes a plurality of magnetoresistive elements positioned externally of said turbine casing.
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7. Apparatus as claimed in claim 1 wherein said flow responsive means includes a rotatable turbine mounted coaxially in a tubular turbine casing through which fluid flows, said magnetic means including a magnetic unit mounted for rotation with said turbine and magnetized in a direction transverse to the angle of rotation thereof, said magnetic unit being mounted for rotation in such a manner as to have no preferred orientation.
Specification