US3729995A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pressure and temperature compensation system for flowmeter
Assignee: Fischer and Porter Co
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Filing: 1971-08-26
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Granted: 1973-05-01
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Expires: 1991-08-26
Abstract
Abstract A pressure and temperature compensation system for a gas flowmeter yielding a pulsatory signal whose frequency is a function of flow rate, which signal is affected by changes in the pressure and temperature of the gas being measured. The system includes sensors generating signals proportional to prevailing values of pressure and temperature, the pressure signal being divided by the temperature signal in a divider-converter adapted to produce a variable duty-cycle signal whose duty cycle is proportional to the quotient of the applied signals. The variable duty-cycle signal is multiplied by the pulsatory flowmeter signal, the product thereof being an output signal whose frequency is directly proportional to volumetric flow corrected with respect to both the temperature and pressure.
Inventors
- 👤 L Kovacs
- 👤 R Schmoock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:20
CPC Classifications
G; G01; G01F; G01F15/00; G01F15/02; G01F15/04; G01F15/043; G01F15/046; G01F1/00; G01F1/05; G01F1/20; G01F1/32; G01F1/325; G01F1/3287
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
196 words
A pressure and temperature compensation system for a gas flowmeter interposed in a gas conduit and yielding a pulsatory signal whose frequency is a function of flow rate an is affected by changes in the pressure and temperature of the gas being measured, said system comprising: A. pressure and temperature sensors disposed in said conduit, said sensors generating pressure and temperature signals proportional to prevailing values of the pressure and temperature of the gas flowing through said conduit, B. a divider-converter coupled to said sensors and adapted to divide said pressure signal by said temperature signal and to generate a variable duty signal whose duty-cycle is proportional to the quotient of the applied signals, C. means to multiply the variable duty-cycle signal produced by the divider-converter with the pulsatory signal produced by the flowmeter, the resultant product being in the form of an output signal whose frequency is directly proportional to volumetric flow corrected with respect to both temperature and pressure, and D. means to frequency-modulate said duty-cycle signal prior to multiplication whereby the resultant duty-cycle signal varies in frequency through a predetermined band though its duty-cycle stays constant Under constant gas pressure and temperature conditions.
Claim 2
Dependent Claim
196 words
A pressure and temperature compensation system for a gas flowmeter interposed in a gas conduit and yielding a pulsatory signal whose frequency is a function of flow rate an is affected by changes in the pressure and temperature of the gas being measured, said system comprising: A. pressure and temperature sensors disposed in said conduit, said sensors generating pressure and temperature signals proportional to prevailing values of the pressure and temperature of the gas flowing through said conduit, B. a divider-converter coupled to said sensors and adapted to divide said pressure signal by said temperature signal and to generate a variable duty signal whose duty-cycle is proportional to the quotient of the applied signals, C. means to multiply the variable duty-cycle signal produced by the divider-converter with the pulsatory signal produced by the flowmeter, the resultant product being in the form of an output signal whose frequency is directly proportional to volumetric flow corrected with respect to both temperature and pressure, and D. means to frequency-modulate said duty-cycle signal prior to multiplication whereby the resultant duty-cycle signal varies in frequency through a predetermined band though its duty-cycle stays constant Under constant gas pressure and temperature conditions.
Claim 3
Dependent Claim
53 words
A system as set forth in claim 1, wherein said flowmeter is constituted by a meter including swirl blades to impart a swirling motion to the gas and an enlarged section to transform the swirling motion into precessional movement, thereby producing cyclic variations in gas velocity and giving rise to said pulsatory signal.
Claim 4
Dependent Claim
19 words
A system as set forth in claim 1, wherein said flowmeter is a vortex-type meter producing said pulsatory signal.
Claim 5
Dependent Claim
24 words
A system as set forth in claim 1, wherein said temperature sensor includes a platinum resistance bulb whose resistance is proportional to absolute temperature.
Claim 6
Dependent Claim
31 words
A system as set forth in claim 1, further including a frequency-to-current converter coupled to said multiplying means to produce an analog output proportional to the frequency of said output signal.
Claim 7
Dependent Claim
37 words
A system as set forth in claim 1, further including means to divide down the frequency of the output signal and to apply the divided-down signal to a numerical register to provide a reading of flow rate.
Claim 8
Dependent Claim
127 words
A system as set forth in claim 1, wherein said divider-converter includes an error amplifier having a feedback loop connected to one input thereof, said loop including a multiplier, the pressure signal being applied to the other input of the error amplifier, a comparator coupled to the output of the error amplifier to compare the signal therefrom with a reference sawtooth voltage to produce a square wave which is applied to one input of said multiplier, the temperature signal being applied to the other input of the multiplier, whereby the output of the multiplier serves to drive the error voltage appearing between the inputs of the error amplifier to zero and the duty-cycle of the resultant square wave is then directly proportional to pressure divided by temperature.
Claim 9
Dependent Claim
35 words
A system as set forth in claim 7, wherein said pressure signal is applied to said error amplifier through a buffer amplifier, and said temperature signal is applied to said multiplier through a buffer amplifier.
Claim 10
Dependent Claim
23 words
A system as set forth in claim 7, wherein said reference sawtooth voltage is derived from a sawtooth oscillator which is frequency modulated.
Claim 11
Dependent Claim
59 words
A system as set forth in claim 1, wherein said means to multiply is constituted by an AND gate to which is applied said duty-cycle signal and said pulsatory flowmeter signal, the duty-cycle input serving alternatively to turn the gate ''''on'''' and ''''off'''' whereby the pulses of the flowmeter signal passes through said gate only during the ''''on'''' intervals.
Claim 12
Dependent Claim
30 words
A system as set forth in claim 10, further including means to shape the pulsatory signal yielded by the flowmeter to produce relatively narrow pulses for application to said gate.
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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) | 1976-04-30 | 1976-10-30 | 1977-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-30 | 1980-10-30 | 1981-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-30 | 1984-10-30 | 1985-05-01 | $7700.00 | Window Closed / Lapsed |