Electromagnetic flowmeter utilizing magnetic fields of a plurality of frequencies
First Claim
1. An electromagnetic flowmeter, comprising:
- measuring pipe means through which a fluid to be measured flows;
first magnetic field generating means for forming a first magnetic field in said measuring pipe means;
second magnetic field generating means for forming a second magnetic field having a frequency different from that of the first magnetic field in said measuring pipe means;
first detecting means for detecting a first electromotive force signal induced by the first magnetic field;
second detecting means for detecting a second electromotive force signal induced by the second magnetic field;
determining means for determining whether the first electromotive force signal is normal and outputting a determination result; and
signal processing means for outputting a signal representing a flow rate of the fluid in accordance with the determination result and in response to the first and second electromotive force signals.
1 Assignment
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Accused Products
Abstract
An electromagnetic flowmeter has first and second magnetic field generating units. The first magnetic field generating unit applies a first magnetic field having a square wave of 4 to 8 Hz to a fluid to be measured. The second magnetic field generating unit applies a second magnetic field having a square wave of 25 to 35 Hz independently of the first magnetic field. A first electromotive force signal induced by the first magnetic field and a second electromotive force signal induced by the second magnetic field are detected by electrodes. A determination circuit determines whether the first electromotive force signal is normal and outputs a determination result. A first signal processing circuit generates a first flow rate signal on the basis of the first electromotive force signal. A second signal processing circuit generates a second flow rate signal on the basis of the second electromotive force signal. A calibration circuit outputs one of the first flow rate signal and the second flow rate signal calibrated by the first flow rate signal as a signal representing a flow rate of the fluid when the determination result represents a normal state, and outputs one of the second flow rate signal and the first flow rate signal calibrated by the second flow rate signal as a signal representing the flow rate when the determination result represents an abnormal state.
40 Citations
21 Claims
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1. An electromagnetic flowmeter, comprising:
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measuring pipe means through which a fluid to be measured flows; first magnetic field generating means for forming a first magnetic field in said measuring pipe means; second magnetic field generating means for forming a second magnetic field having a frequency different from that of the first magnetic field in said measuring pipe means; first detecting means for detecting a first electromotive force signal induced by the first magnetic field; second detecting means for detecting a second electromotive force signal induced by the second magnetic field; determining means for determining whether the first electromotive force signal is normal and outputting a determination result; and signal processing means for outputting a signal representing a flow rate of the fluid in accordance with the determination result and in response to the first and second electromotive force signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An electromagnetic flowmeter comprising:
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path means through which a fluid to be measured flows; first magnetic field generating means, having a first wiring and a first magnetic path, for generating a first magnetic field in said path means to generate a first electromotive force signal; second magnetic field generating means, having a second winding and a second magnetic path, for generating a second magnetic field in said path means to generate a second electromotive force signal; the second magnetic field having a frequency higher than the first magnetic field; the first and second magnetic fields being independently applied to the fluid to be measured, the second magnetic path having better magnetic characteristics than those of the first magnetic path, and the first and second electromotive force signals being substantially free from mutual interference; means for independently detecting the first electromotive force signal induced by the first magnetic field and the second electromotive force signal induced by the second magnetic field; means for determining whether the first electromotive force signal is normal and outputting a determination result; first flow rate measuring means for generating a first flow rate designation signal representing a flow rate of the fluid on the basis of the first electromotive force signal; second flow rate measuring means for generating a second flow rate designation signal representing a flow rate of the fluid on the basis of the second electromotive force signal; and calibrating means, responsive to the determination result from said determining means, for outputting a signal representing the flow rate of the fluid on the basis of the first and second flow rate designation signals. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A method for detecting a flow rate, comprising:
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step of generating a first magnetic field and a second magnetic field having a frequency different from that of the first magnetic field, to a fluid to be measured; step of detecting a first electromotive force signal induced by the first magnetic field and a second electromotive force signal induced by the second magnetic field; step of determining whether the first electromotive force signal is normal and outputting a determination result; and step of outputting a signal representing a flow rate of the fluid in accordance with the determination result and in response to the first and second electromotive force signals.
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Specification