US3751980A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low power electromagnetic flowmeter providing accurate zero set
Assignee: National Aeronautics and Space Administration
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Filing: 1971-11-12
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Granted: 1973-08-14
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Expires: 1991-11-12
Abstract
Abstract A low power, small size electromagnetic flowmeter system is provided which produces a zero output signal for zero flow. The system comprises an air core type electromagnetic flow transducer, a field current supply circuit for the transducer coils and a pre-amplifier and demodulation circuit connected to the output of the transducer. To prevent spurious signals at zero flow, separate, isolated power supplies are provided for the two circuits. The demodulator includes a pair of synchronous rectifiers which are controlled by signals from the field current supply circuit. Pulse transformers connected in front of the synchronous rectifiers provide isolation between the two circuits.
Inventors
- 👤 T Fryer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 20:31
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/02; A61B5/026; A61B5/0265; G; G01; G01F; G01F1/00; G01F1/56; G01F1/58; G01F1/60
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
151 words
An electromagnetic flowmeter system comprising a flow transducer for producing an electrical output signal in accordance with sensed flow and including at least one coil for generating an electromagnetic field in the area in which flow is to be sensed, a field current supply circuit for supplying current to said at least one coil; a demodulation circuit for converting said electrical output signal to a further, flow indication signal; a first power supply for said field current supply circuit; a second power supply for said demodulation circuit separate from and isolated from said first power supply circuit; said demodulation circuit comprising first and second synchronous rectifiers, said field current supply circuit including synchronizing means for producing synchronized gating signals for said synchronous rectifiers and said system further comprising pulse transformer means connected between said synchronizing means and said synchronous rectifiers for isolating said field current supply circuit from said demodulation circuit.
Claim 2
Dependent Claim
151 words
An electromagnetic flowmeter system comprising a flow transducer for producing an electrical output signal in accordance with sensed flow and including at least one coil for generating an electromagnetic field in the area in which flow is to be sensed, a field current supply circuit for supplying current to said at least one coil; a demodulation circuit for converting said electrical output signal to a further, flow indication signal; a first power supply for said field current supply circuit; a second power supply for said demodulation circuit separate from and isolated from said first power supply circuit; said demodulation circuit comprising first and second synchronous rectifiers, said field current supply circuit including synchronizing means for producing synchronized gating signals for said synchronous rectifiers and said system further comprising pulse transformer means connected between said synchronizing means and said synchronous rectifiers for isolating said field current supply circuit from said demodulation circuit.
Claim 3
Dependent Claim
31 words
An electromagnetic flowmeter system as claimed in claim 1 wherein said field current supply circuit includes an astable multivibrator and a bistable multivibrator connected to the output of said astable miltivibrator.
Claim 4
Dependent Claim
80 words
An electromagnetic flowmeter system as claimed in claim 2 wherein said synchronizing means comprises first AND gate having a first input connected to a first output of said astable multivibrator and a second input connected to a first output of said bistable miltivibrator and a second AND gate having a first input connected to a second, 180* phase spaced output of said astable miltivibrator and a second input connected to a second, 180* phase spaced output of said bistable multi-vibrator.
Claim 5
Dependent Claim
20 words
An electromagnetic flowmeter system as claimed in claim 2 wherein said flow transducer comprises an air core type flow transducer.
Claim 6
Dependent Claim
50 words
An electromagnetic flowmeter system as claimed in claim 2 wherein said pulse transformer means comprises first and second pulse transformers, said system further comprising first and second bistable multivibrators individually connected to the outputs of said pulse transformers for restoring the wave shapes of the pulses entering the pulse transformers.
Claim 7
Dependent Claim
25 words
An electromagnetic flowmeter system as claimed in claim 5 wherein said pulse transformers convert an incoming pulse to first and second pulses of one-microsecond duration.
Claim 8
Dependent Claim
45 words
An electromagnetic flowmeter system as claimed in claim 2 wherein said transducer includes a plurality of electrodes and said demodulation circuit includes a differential pre-amplifier connected to said electrodes, one input of each of said synchronous rectifiers being connected to the output of said pre-amplifier.
Claim 9
Dependent Claim
27 words
An electromagnetic flowmeter system as claimed in claim 7 wherein said demodulation circuit further comprises a differential operational amplifier connected To the outputs of said synchronous rectifiers.
Claim 10
Dependent Claim
30 words
An electromagnetic flowmeter system as claimed in claim 8 wherein said field current supply circuit includes a power amplifier connected between said bistable multivibrator and said at least one coil.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-13 | 1977-02-12 | 1977-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-13 | 1981-02-12 | 1981-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-13 | 1985-02-12 | 1985-08-14 | $7700.00 | Window Closed / Lapsed |