Patent US4734609A successfully refreshed from Google Patents.
US4734609A
Expired / Lapsed
US
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Gas density transducer
Assignee: Calogic Corp
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Filing: 1986-07-25
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Granted: 1988-03-29
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Expires: 2006-07-25
Abstract
Abstract An improved gas density transducer which compares the resonant frequency of an enclosed, reference tuning fork crystal oscillator with the resonant frequency of a detector tuning fork crystal oscillator exposed to the surrounding gas. The frequency of oscillation of the detector crystal oscillator exposed will vary in accordance with the gas density because of the motional resistance of the gas to vibrations of the tuning fork oscillator. The frequency of the detector oscillator can be compared to the frequency of the reference oscillator to determine the gas density.
Inventors
- 👤 Richard Jasmine
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:54
CPC Classifications
G; G01; G01N; G01N9/00; G01N9/002; G01L; G01L9/00; G01L9/0001; G01L9/0008; G01L9/0022; G01N2009/004; G01N2009/006
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
65 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber having a fixed gas density; a detector tuning fork crystal oscillator exposed to the density of the gas surrounding said transducer; and means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals.
Claim 2
Dependent Claim
65 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber having a fixed gas density; a detector tuning fork crystal oscillator exposed to the density of the gas surrounding said transducer; and means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals.
Claim 3
Dependent Claim
13 words
The transducer of claim 1 wherein said fixed gas density is highly evacuated.
Claim 4
Dependent Claim
33 words
The transducer of claim 1 wherein said means for comparing comprises a mixer producing a beat frequency proportional to the difference between the frequencies of the signals from said reference and detector oscillators.
Claim 5
Dependent Claim
34 words
The transducer of claim 3 further comprising first and second amplifiers coupled between said reference and detector oscillators, respectively, and said mixer, and a Schmitt trigger buffer coupled to an output of said mixer.
Claim 6
Dependent Claim
18 words
The transducer of claim 4 further comprising a display coupled to an output of said Schmitt trigger buffer.
Claim 7
Dependent Claim
37 words
The transducer of claim 1 further comprising means for varying the frequency of said reference oscillator responsive to changes in temperature to substantially offset changes in frequency caused by variations in gas density due to temperature changes.
Claim 8
Dependent Claim
60 words
The transducer of claim 6 wherein said means for varying comprises a capacitor coupled at a first lead to said reference oscillator, a series combination of a resistor and a varactor diode having a junction coupled to a second lead of said capacitor, and a thermistor coupled in parallel with said series combination of said varactor diode and said resistor.
Claim 9
Dependent Claim
28 words
The transducer of claim 1 further comprising a container surrounding said detector oscillator, said container having a hole coupling the interior of said container to the surrounding gas.
Claim 10
Dependent Claim
12 words
The transducer of claim 8 further comprising a diaphram covering said hole.
Claim 11
Dependent Claim
111 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber in a substantial vacuum; a detector tuning fork crystal oscillator exposed to the pressure of the gas surrounding said transducer; a first amplifier coupled to said detector oscillator; a second amplifier coupled to said reference oscillator, said second amplifier including means for varying the frequency of said reference oscillator responsive to changes in temperature to substantially offset changes in frequency caused by variations in gas density due to said changes in temperature; and a mixer for producing a beat frequency proportional to the difference between the frequencies of output signals of said first and second amplifiers.
Claim 12
Dependent Claim
111 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber in a substantial vacuum; a detector tuning fork crystal oscillator exposed to the pressure of the gas surrounding said transducer; a first amplifier coupled to said detector oscillator; a second amplifier coupled to said reference oscillator, said second amplifier including means for varying the frequency of said reference oscillator responsive to changes in temperature to substantially offset changes in frequency caused by variations in gas density due to said changes in temperature; and a mixer for producing a beat frequency proportional to the difference between the frequencies of output signals of said first and second amplifiers.
Claim 13
Dependent Claim
83 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber having a fixed gas density; a detector tuning fork crystal oscillator exposed to the density of the gas surrounding said transducer; means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals; and temperature compensation means for varying said output signal inversely proportional to the change in gas density with temperature.
Claim 14
Dependent Claim
83 words
A gas density transducer comprising: a reference tuning fork crystal oscillator sealed within a chamber having a fixed gas density; a detector tuning fork crystal oscillator exposed to the density of the gas surrounding said transducer; means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals; and temperature compensation means for varying said output signal inversely proportional to the change in gas density with temperature.
Claim 15
Dependent Claim
60 words
The transducer of claim 11 wherein said temperature compensation means comprises a capacitor coupled at a first lead to said refernece oscillator, a series combination of a resistor and a varactor diode having a junction coupled to a second lead of said capacitor, and a thermistor coupled in parallel with said series combination of said varactor diode and said resistor.
Claim 16
Dependent Claim
116 words
A pressure transducer comprising: a reference tuning fork crystal oscillator sealed with a first chamber having a fixed gas density; a detector tuning fork crystal oscillator mounted in a second chamber filled with a gas and having an opening coupling the interior of said chamber to the exterior of said transducer; a flexible diaphragm covering said opening so that changes in pressure outside said transducer will move said diaphragm to change the volume of said second chamber and thus vary the gas density in said second chamber; and means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals.
Claim 17
Dependent Claim
116 words
A pressure transducer comprising: a reference tuning fork crystal oscillator sealed with a first chamber having a fixed gas density; a detector tuning fork crystal oscillator mounted in a second chamber filled with a gas and having an opening coupling the interior of said chamber to the exterior of said transducer; a flexible diaphragm covering said opening so that changes in pressure outside said transducer will move said diaphragm to change the volume of said second chamber and thus vary the gas density in said second chamber; and means for comparing the frequency of signals from said reference and detector oscillators and producing an output signal proportional to the difference in the frequencies of said signals.
Claim 18
Dependent Claim
13 words
The transducer of claim 13 wherein said fixed gas density is highly evacuated.
Claim 19
Dependent Claim
33 words
The transducer of claim 13 wherein said means for comparing comprises a mixer producing a beat frequency proportional to the difference between the frequencies of the signals from said reference and detector oscillators.
Claim 20
Dependent Claim
25 words
The transducer of claim 13 further comprising temperature compensation means for varying said output signal inversely proportional to the change in gas density with temperature.
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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) | 1991-03-29 | 1991-09-28 | 1992-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-29 | 1995-09-28 | 1996-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-29 | 1999-09-28 | 2000-03-29 | $7700.00 | Window Closed / Lapsed |