US4169375A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic flowmeter
Assignee: Yokogawa Electric Corp
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Filing: 1978-03-21
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Granted: 1979-10-02
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Expires: 1998-03-21
Abstract
Abstract A magnetic flowmeter whose electromagnet is excited by a low-frequency excitation current, the flowmeter including flow tube electrodes yielding a flow rate signal. A reference voltage-detecting transformer is provided in the excitation circuit to produce a reference voltage that reflects fluctuations in the excitation current. Fluctuations in the flow rate signal as a result of fluctuations in the excitation current are eliminated by dividing the flow rate signal by the reference-voltage signal.
Inventors
- 👤 Kazuie Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:45
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/56; G01F1/58; G01F1/60
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
209 words
In combination with a magnetic flowmeter in which the fluid to be metered is conducted through a flow tube having detecting electrodes, the fluid intercepting the magnetic field produced by an electromagnet having an excitation coil to induce a flow rate signal in said electrodes, said flow rate signal being subject to unwanted fluctuations as a result of fluctuations in the current exciting said coil, said system comprising: A. rectification means coupled to a commercial power line source whose a-c power has a relatively high-frequency to produce a direct-current voltage, and means including a periodically-actuated switch to apply said voltage across said coil at a rate whose frequency is low relative to the power line frequency to cause an excitation current to flow through said coil; B. a reference voltage-detecting transformer whose primary is interposed between said a-c source and said rectification means and whose secondary yields a voltage that depends on fluctuations in said excitation current and having a frequency corresponding to the power line frequency; C. means coupled to said secondary to derive a reference-voltage signal from said secondary; and D. means to apply said reference voltage signal and said flow rate signal to a converter to produce an output flow rate signal free of said fluctuations.
Claim 2
Dependent Claim
209 words
In combination with a magnetic flowmeter in which the fluid to be metered is conducted through a flow tube having detecting electrodes, the fluid intercepting the magnetic field produced by an electromagnet having an excitation coil to induce a flow rate signal in said electrodes, said flow rate signal being subject to unwanted fluctuations as a result of fluctuations in the current exciting said coil, said system comprising: A. rectification means coupled to a commercial power line source whose a-c power has a relatively high-frequency to produce a direct-current voltage, and means including a periodically-actuated switch to apply said voltage across said coil at a rate whose frequency is low relative to the power line frequency to cause an excitation current to flow through said coil; B. a reference voltage-detecting transformer whose primary is interposed between said a-c source and said rectification means and whose secondary yields a voltage that depends on fluctuations in said excitation current and having a frequency corresponding to the power line frequency; C. means coupled to said secondary to derive a reference-voltage signal from said secondary; and D. means to apply said reference voltage signal and said flow rate signal to a converter to produce an output flow rate signal free of said fluctuations.
Claim 3
Dependent Claim
14 words
The combination as set forth in claim 1, wherein said converter is a divider.
Claim 4
Dependent Claim
21 words
The combination as set forth in claim 1, further including a diode shunted across said excitation coil to eliminate transient spikes.
Claim 5
Dependent Claim
26 words
The combination as set forth in claim 1, wherein said means coupled to said secondary to derive the reference voltage signal therefrom is a rectifier bridge.
Claim 6
Dependent Claim
21 words
The combination as set forth in claim 4, further including a load resistor connected across the output junctions of said bridge.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-10-01 | 1983-04-02 | 1983-10-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-10-01 | 1987-04-02 | 1987-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-10-01 | 1991-04-02 | 1991-10-02 | $7700.00 | Window Closed / Lapsed |