US3719083A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flowmeters
Assignee: National Research Development Corp UK
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Filing: 1971-03-29
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Granted: 1973-03-06
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Expires: 1991-03-29
Abstract
Abstract A flowmeter comprises an electrically resistive sensing element which is heated electrically while exposed to a stream of fluid. The heating power is supplied in the form of a train of identical pulses spaced so that thermal equilibrium between the sensing element and the fluid is achieved before each pulse. Variations in the fluid flow rate are detected by sensing variations in the rate of change of resistance of the sensing element during a pulse.
Inventors
- 👤 W Morris
- 👤 N Lindsay
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:15
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/02; A61B5/026; A61B5/0275; G; G01; G01F; G01F1/00; G01F1/68; G01F1/684; G01F1/688; G01F1/69; G01F1/692; G01F1/696; G01F1/698; G01F1/6986
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
142 words
A flowmeter comprising: electrically resistive sensing means for exposure to a stream of fluid under investigation; means for heating the sensing means including means for generating a train of identical electrical pulses having a duration invariant with flow rate separated by intervals sufficiently long to ensure that the sensing means is in thermal equilibrium with the fluid at the beginning of each pulse and means for applying said pulses to said sensing means; flow rate sensing means connected to said resistive sensing means including means for measuring an output signal of said resistive sensing means indicating the impedance thereof for a selected interval at the beginning and end of each pulse, and responsive to said signals indicating average rate of change of impedance of said sensing means during each pulse for producing a signal which varies as a function of flow rate.
Claim 2
Dependent Claim
142 words
A flowmeter comprising: electrically resistive sensing means for exposure to a stream of fluid under investigation; means for heating the sensing means including means for generating a train of identical electrical pulses having a duration invariant with flow rate separated by intervals sufficiently long to ensure that the sensing means is in thermal equilibrium with the fluid at the beginning of each pulse and means for applying said pulses to said sensing means; flow rate sensing means connected to said resistive sensing means including means for measuring an output signal of said resistive sensing means indicating the impedance thereof for a selected interval at the beginning and end of each pulse, and responsive to said signals indicating average rate of change of impedance of said sensing means during each pulse for producing a signal which varies as a function of flow rate.
Claim 3
Dependent Claim
142 words
A flowmeter comprising: electrically resistive sensing means for exposure to a stream of fluid under investigation; means for heating the sensing means including means for generating a train of identical electrical pulses having a duration invariant with flow rate separated by intervals sufficiently long to ensure that the sensing means is in thermal equilibrium with the fluid at the beginning of each pulse and means for applying said pulses to said sensing means; flow rate sensing means connected to said resistive sensing means including means for measuring an output signal of said resistive sensing means indicating the impedance thereof for a selected interval at the beginning and end of each pulse, and responsive to said signals indicating average rate of change of impedance of said sensing means during each pulse for producing a signal which varies as a function of flow rate.
Claim 4
Dependent Claim
142 words
A flowmeter comprising: electrically resistive sensing means for exposure to a stream of fluid under investigation; means for heating the sensing means including means for generating a train of identical electrical pulses having a duration invariant with flow rate separated by intervals sufficiently long to ensure that the sensing means is in thermal equilibrium with the fluid at the beginning of each pulse and means for applying said pulses to said sensing means; flow rate sensing means connected to said resistive sensing means including means for measuring an output signal of said resistive sensing means indicating the impedance thereof for a selected interval at the beginning and end of each pulse, and responsive to said signals indicating average rate of change of impedance of said sensing means during each pulse for producing a signal which varies as a function of flow rate.
Claim 5
Dependent Claim
63 words
A flowmeter according to claim 1, in which each of said pulses is of duration sufficiently short to ensure that the temperature of the sensing means increases continuously throughout the length of the pulse, and said flow rate sensing means is responsive to the difference between the values of the resistance of the sensing means at the beginning and end of each pulse.
Claim 6
Dependent Claim
28 words
A flowmeter according to claim 1, further comprising temperature sensing means responsive to the value of the resistance of the sensing means at the beginning of each pulse.
References Cited (Backward Citations)
US3498128A
Cited
US3587318A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-05 | 1976-09-04 | 1977-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-05 | 1980-09-04 | 1981-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-05 | 1984-09-04 | 1985-03-06 | $7700.00 | Window Closed / Lapsed |