Variable frequency magnetic flowmeter
First Claim
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1. An apparatus comprising:
- a pipe section for process flow;
a coil for generating a magnetic field across the pipe section;
a current source for energizing the coil to generate the magnetic field, wherein the current source energizes the coil at a plurality of different pulse frequencies, and the plurality of different pulse frequencies includes at least three pulse frequencies spaced so that their harmonics do not overlap so that repeated harmonic sampling of a noise signal is avoided and bias from the noise signal is reduced;
an electrode for sensing an electromotive force induced across the process flow by the magnetic field;
a processor for calculating a function of the electromotive force at the plurality of different pulse frequencies, and for generating a flow output based on the function; and
wherein the function comprises a weighted average of the electromotive force at each of the different pulse frequencies, wherein the weighted average is weighted based on a difference between the electromotive force at each of the different pulse frequencies and a common mean, and wherein the weighted average excludes pulse frequencies based on the difference.
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Abstract
An apparatus comprises a pipe section for process flow, a coil for generating a magnetic field across the pipe section, a current source for energizing the coil to generate the magnetic field, and an electrode for sensing an electromotive force induced across the process flow by the magnetic field. The current source energizes the coil at a plurality of different pulse frequencies. A processor calculates a function of the electromotive force at the plurality of different pulse frequencies, and generates a flow output based on the function.
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Citations
12 Claims
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1. An apparatus comprising:
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a pipe section for process flow; a coil for generating a magnetic field across the pipe section; a current source for energizing the coil to generate the magnetic field, wherein the current source energizes the coil at a plurality of different pulse frequencies, and the plurality of different pulse frequencies includes at least three pulse frequencies spaced so that their harmonics do not overlap so that repeated harmonic sampling of a noise signal is avoided and bias from the noise signal is reduced; an electrode for sensing an electromotive force induced across the process flow by the magnetic field; a processor for calculating a function of the electromotive force at the plurality of different pulse frequencies, and for generating a flow output based on the function; and wherein the function comprises a weighted average of the electromotive force at each of the different pulse frequencies, wherein the weighted average is weighted based on a difference between the electromotive force at each of the different pulse frequencies and a common mean, and wherein the weighted average excludes pulse frequencies based on the difference. - View Dependent Claims (2, 3, 4, 5)
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6. A magnetic flowmeter comprising:
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a pipe section, the pipe section having an inner diameter and an outer diameter; a coil proximate the outer diameter of the pipe section; a pulsed current source connected to the coil, wherein the pulsed current source provides a plurality of different pulse frequencies, and the plurality of different pulse frequencies includes at least three pulse frequencies spaced so that their harmonics do not overlap so that repeated harmonic sampling of a noise signal is avoided and bias from the noise signal is reduced; electrodes extending from the outer diameter of the pipe section to the inner diameter of the pipe section, wherein the electrodes sense an electromotive force across the pipe section; a processor connected to the electrodes, wherein the processor generates a flow output as a function of the electromotive force at the plurality of different pulse frequencies; and wherein the function comprises a weighted average of the electromotive force at each of the different pulse frequencies, wherein the weighted average is weighted based on a difference between the electromotive force at each of the different pulse frequencies and a common mean, and wherein the weighted average excludes pulse frequencies based on the difference. - View Dependent Claims (7, 8, 9)
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10. A method of measuring flow, the method comprising:
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generating a pulsed magnetic field across a process flow; sensing an electromotive force induced across the process flow by the pulsed magnetic field; varying a frequency of the pulsed magnetic field, wherein the pulsed magnetic field has a plurality of different pulse frequencies, and the plurality of different pulse frequencies includes at least three pulse frequencies spaced so that their harmonics do not overlap so that repeated harmonic sampling of a noise signal is avoided and bias from the noise signal is reduced; calculating a weighted average of the electromotive force at the plurality of different pulse frequencies, wherein the weighted average is weighted based on a difference between the electromotive force at each of the different pulse frequencies and a common mean; excluding pulse frequencies based on the difference; and generating a flow output based on the average. - View Dependent Claims (11, 12)
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Specification