Patent US3894430A successfully refreshed from Google Patents.
US3894430A
Expired / Lapsed
US
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Electromagnetic flowmeter
Assignee: Fischer and Porter Co
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Filing: 1973-07-27
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Granted: 1975-07-15
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Expires: 1993-07-27
Abstract
Abstract An electromagnetic flowmeter in which a fluid whose flow rate is to be measured is conducted through a flow tube and intersects a magnetic field established by an electromagnet coil to induce a signal voltage across electrodes mounted in the tube. The coil is energized from an A-C power line through a current limiter which functions to maintain the amplitude of the alternating field constant during an extended period of time.
Inventors
- 👤 Theodor Rummel
- 👤 Rainer Hentschel
- 👤 Eggert Appel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 09:44
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/56; G01F1/58; G01F1/60
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
174 words
In an electromagnetic flowmeter operated from a standard alternating-current power line producing a sinusoidal current, said flowmeter having a flow tube provided with a pair of measuring electrodes and an electromagnetic coil for establishing a field which is intersected by a fluid passing through the tube to produce a signal voltage across said electrodes whose amplitude is a funtion of flow rate, said signal being applied to an indicator; the combination comprising: A. Means including a limiter having a bipolar control element to supply said current from said alternating-current power line to said coil and a controller operatively coupled to said control element to limit the amplitude of said current during a predetermined interval in the course of each positive and negative half wave to maintain the amplitude substantially constant during said intervals, and B. Scanner means interposed between said electrodes and said indicator and operatively coupled to said limiter means to transmit the signal voltage from said electrodes to said indicator only during said interval, whereby the effects of quadrature voltages are avoided.
Claim 2
Dependent Claim
174 words
In an electromagnetic flowmeter operated from a standard alternating-current power line producing a sinusoidal current, said flowmeter having a flow tube provided with a pair of measuring electrodes and an electromagnetic coil for establishing a field which is intersected by a fluid passing through the tube to produce a signal voltage across said electrodes whose amplitude is a funtion of flow rate, said signal being applied to an indicator; the combination comprising: A. Means including a limiter having a bipolar control element to supply said current from said alternating-current power line to said coil and a controller operatively coupled to said control element to limit the amplitude of said current during a predetermined interval in the course of each positive and negative half wave to maintain the amplitude substantially constant during said intervals, and B. Scanner means interposed between said electrodes and said indicator and operatively coupled to said limiter means to transmit the signal voltage from said electrodes to said indicator only during said interval, whereby the effects of quadrature voltages are avoided.
Claim 3
Dependent Claim
77 words
In a flowmeter as set forth in claim 1 wherein said limiter means includes said bipolar control element and a resistor, said element and said resistor being connected in a series with said coil to said A-C power line, and wherein said controller for governing the operation of said control element is arranged to compare a set point determined by the desired constant current amplitude and a process variable determined by the voltage drop across said resistor.
Claim 4
Dependent Claim
36 words
In a flowmeter as set forth in claim 2 wherein said process variable is derived by means of an operational amplifier whose output is coupled to said controller and whose inputs are connected across said resistor.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-07-14 | 1979-01-13 | 1979-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-14 | 1983-01-13 | 1983-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-14 | 1987-01-13 | 1987-07-15 | $7700.00 | Window Closed / Lapsed |