Magnetic flow meter
First Claim
1. A magnetic flow meter comprising:
- a conduit operable to guide a flow along a flow path;
a magnetic field generator operable to generate an alternating magnetic field at a drive frequency across the flow path;
a flow sensor operable to sense electromagnetic fields generated across the flow path and to output a corresponding flow sensor signal including;
(a) an electric field component at the drive frequency and at a first phase, which electric field component varies with an electric field generated by the interaction of the magnetic field generated by said magnetic field generator and said flow; and
(b) an interfering component at the drive frequency and at a second different phase;
a magnetic field sensor operable to sense the magnetic field generated by said magnetic field generator and to output a corresponding magnetic field sensor signal at said drive frequency at a phase related to said second phase;
a calibration processor operable to process said magnetic field sensor signal to generate an alternating calibration control signal at said drive frequency whose phase depends upon the phase of said magnetic field sensor signal;
a first processing circuit responsive to the calibration control signal and operable to process the flow sensor signal to determine a measure of the strength of the electric field component thereof;
a second processing circuit operable to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
a measurement processor operable to determine a measure of the flow in said conduit in dependence upon the determined measure of strength of said electric field component and the determined measure of strength of said magnetic field sensor signal.
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Accused Products
Abstract
A magnetic flow meter includes a cylindrical vessel within which electrodes are placed directly opposite each other about a magnetically permeable core. In that way, two flow channels are obtained in the vessel. A common magnetic field is applied across both flow channels. The magnetic flow meter is used in conjunction with a controller which monitors amplitude modulated signals representative of applied magnetic field and induced electric field. These amplitude modulated signals are passed to Sigma-Delta modulators, which directly digitise the amplitude modulated AC signals into digital pulses. The controller is capable of monitoring reverse flow through the meter, and to store results until forward flow resumes. Moreover, the controller generates a driving signal for coils which generates a magnetic field, the coil being placed in conjunction with a capacitor which causes resonance. This reduces power consumption by the coil in driving the meter.
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Citations
33 Claims
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1. A magnetic flow meter comprising:
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a conduit operable to guide a flow along a flow path;
a magnetic field generator operable to generate an alternating magnetic field at a drive frequency across the flow path;
a flow sensor operable to sense electromagnetic fields generated across the flow path and to output a corresponding flow sensor signal including;
(a) an electric field component at the drive frequency and at a first phase, which electric field component varies with an electric field generated by the interaction of the magnetic field generated by said magnetic field generator and said flow; and
(b) an interfering component at the drive frequency and at a second different phase;
a magnetic field sensor operable to sense the magnetic field generated by said magnetic field generator and to output a corresponding magnetic field sensor signal at said drive frequency at a phase related to said second phase;
a calibration processor operable to process said magnetic field sensor signal to generate an alternating calibration control signal at said drive frequency whose phase depends upon the phase of said magnetic field sensor signal;
a first processing circuit responsive to the calibration control signal and operable to process the flow sensor signal to determine a measure of the strength of the electric field component thereof;
a second processing circuit operable to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
a measurement processor operable to determine a measure of the flow in said conduit in dependence upon the determined measure of strength of said electric field component and the determined measure of strength of said magnetic field sensor signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
a second electrode support including an elongated portion positioned adjacent the inner surface of the flow tube and at least one flow divider extending inward toward the core, said second electrode support having at least one rail, said rail being circumferentially aligned with the second electrode.
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24. A magnetic flow meter according to claim 23, wherein the at least one rail of the first electrode support comprises first and second flow dividers axially spaced from each other, the first electrode being positioned between the first and second flow dividers;
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the at least one rail of the second electrode support comprises third and fourth flow dividers axially spaced apart from each other, the second electrode being positioned between the third and fourth flow dividers.
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25. A magnetic flow meter according to claim 23, wherein the core includes a through-bore extending from a side of the core adjacent a radially inner side of the first electrode to a side of the core adjacent a radially inner side of the second electrode, wherein the first electrode includes a through-bore and further comprising an electrode lead which passes through the through-bore of the core and the through-bore of the first electrode and which is connected to the second electrode for connecting the second electrode to the first processing circuit.
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26. A magnetic flow meter according to claim 25, wherein the first electrode support includes an axially extending electrode passage, and wherein the electrode lead for the second electrode extends within said electrode passage to an exterior of the conduit together with an electrode lead for connecting the first electrode to the first processing circuit.
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27. A magnetic flow meter according to claim 23, wherein at least a portion of the at least one flow divider of the first electrode support contacts the core and at least a portion of the at least one flow divider of the second electrode support contacts the core, thereby holding the core in position.
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28. A magnetic flow meter according to claim 8, wherein said first and second electrodes are formed from a graphite material.
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29. A magnetic flow meter according to claim 1, having a periodic measurement cycle, wherein said first and second processing circuits are operable to process the respective signals continuously during each measurement cycle and to accumulate the respective sensor signal strengths in the measurement cycle and wherein said measurement processor is operable to determine a measure of the flow along said flow path at the end of each measurement cycle using the strength measures accumulated during that cycle.
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30. A domestic water meter comprising:
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a conduit operable to guide water along a flow path;
a magnetic field generator operable to generate an alternating magnetic field at a drive frequency across the flow path;
a flow sensor operable to sense electromagnetic fields generated across the flow path and to output a corresponding flow sensor signal including;
(a) an electric field component at the drive frequency and at a first phase, which electric field component varies with an electric field generated by the interaction of the magnetic field generated by said magnetic field generator and the water flowing along said flow path; and
(b) an interfering component at the drive frequency and at a second different phase;
a magnetic field sensor operable to sense the magnetic field generated by said magnetic field generator and to output a corresponding magnetic field sensor signal at said drive frequency at a phase related to said second phase;
a calibration processor operable to process said magnetic field sensor signal to generate an alternating calibration control signal at said drive frequency whose phase depends upon the phase of said magnetic field sensor signal;
a first processing circuit responsive to the calibration control signal and operable to process the flow sensor;
signal to determine a measure of the strength of the electric field component thereof;
a second processing circuit operable to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
a measurement processor operable to determine a measure of the flow of water in said conduit in dependence upon the determined measure of strength of said electric field component and the determined measure of strength of said magnetic field sensor signal.
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31. A process flow control meter comprising:
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a conduit operable to guide a flow along a flow path;
a magnetic field generator operable to generate an alternating magnetic field at a drive frequency across the flow path;
a flow sensor operable to sense electromagnetic fields generated across the flow path and to output a corresponding flow sensor signal including;
(a) an electric field component at the drive frequency and at a first phase, which electric field component varies with an electric field generated by the interaction of the magnetic field generated by said magnetic field generator and said flow; and
(b) an interfering component at the drive frequency and at a second different phase;
a magnetic field sensor operable to sense the magnetic field generated by said magnetic field generator and to output a corresponding magnetic field sensor signal at said drive frequency at a phase related to said second phase;
a calibration processor operable to process said magnetic field sensor signal to generate an alternating calibration control signal at said drive frequency whose phase depends upon the phase of said magnetic field sensor signal;
a first processing circuit responsive to the calibration control signal and operable to process the flow sensor signal to determine a measure of the strength of the electric field component thereof;
a second processing circuit operable to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
a measurement processor-operable to-determine a measure of the flow in said conduit in dependence upon the determined measure of strength of said electric field component and the determined measure of strength of said magnetic field sensor signal.
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32. A method of measuring a flow rate of a fluid comprising:
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providing a conduit operable to guide the fluid along a flow path;
generating an alternating magnetic field at a drive frequency across the flow path;
a first sensing step of sensing electromagnetic fields generated across the flow path and outputting a corresponding flow sensor signal including;
(a) an electric field component at the drive frequency and at a first phase, which electric field component varies with an electric field generated by the interaction of the generated magnetic field and said flow; and
(b) an interfering component at the drive frequency and at a second different phase;
a second sensing step of sensing the magnetic field generated in said magnetic field generating step and outputting a corresponding magnetic field sensor signal at said drive frequency at a phase related to said second phase;
using a calibration processor to process said magnetic field sensor signal to generate an alternating calibration control signal at said drive frequency whose phase depends upon the phase of said magnetic field sensor signal;
using a first processing circuit responsive to the calibration control signal, to process the flow sensor signal to determine a measure of the strength of the electric field component thereof;
using a second processing circuit to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
determining a measure of the flow in said conduit in dependence upon the determined measure of strength of said electric field component and the determined measure of strength of said magnetic field sensor signal.
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33. A magnetic flow meter comprising:
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a conduit operable to guide a flow along a flow path;
a magnetic field generator operable to generate a magnetic field across the flow path;
an electric field sensor operable to sense an electric field generated across the flow path by the interaction of the magnetic field generated by said magnetic field generator and the flow in said flow path and to output a corresponding electric field sensor signal;
a magnetic field sensor operable to sense the magnetic field generated by said magnetic field generator and to output a corresponding magnetic field sensor signal;
a first processing circuit operable to process the electric field sensor signal to determine a measure of the strength of the electric field sensor signal;
a second processing circuit operable to process the magnetic field sensor signal to determine a measure of the strength of the magnetic field sensor signal; and
a measurement processor operable to determine a measure of the flow in said conduit in dependence upon the determined measure of strength of said electric field sensor signal and the determined measure of strength of said magnetic field sensor signal;
wherein said magnetic flow meter has a periodic measurement cycle, wherein said first and second processing circuits are operable to process the respective sensor signals continuously during each measurement cycle and to accumulate the respective sensor signal strengths in the measurement cycle and wherein said measurement processor is operable to determine a measure of the flow along said flow path at the end of each measurement cycle using the strength measures accumulated during that cycle.
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Specification