US3689907A
Expired / Lapsed
US
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Dewpoint monitor
Assignee: Robbins Aviation Inc
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Filing: 1970-08-03
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Granted: 1972-09-05
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Expires: 1990-08-03
Abstract
Abstract A monitor for compressed air and other gases signaling the moisture level thereof relative to a predetermined dewpoint. The basic sensor is a piezoelectric quartz crystal coated with a hygroscopic material which adsorbs moisture and changes the overall mass of the crystal and its oscillating frequency. This frequency is compared to the frequency of a reference crystal oscillator and the difference frequency is operated on in an electronic circuit to signal the moisture content of a compressed gas relative to the predetermined dewpoint.
Inventors
- 👤 Ciro Guajardo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 03:05
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/02; G01N29/036; G01N2291/00; G01N2291/02; G01N2291/025; G01N2291/0256
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
234 words
A dewpoint monitor for gases comprising: a first oscillator; means responsive to humidity for controlling the frequency of the output of said first oscillator; means subjecting said responsive means to contact with a gas being monitored; a second oscillator having a substantially constant frequency output; means for mixing said oscillator outputs to secure the difference frequency therebetween; means for indicating a dry condition of the gas being monitored below a predetermined dewpoint; means for indicating a wet condition of the gas being monitored above said predetermined dewpoint; means responsive to said difference frequency for determining whether the gas being monitored is in a dry or wet condition and for actuating the appropriate indicating means for the condition determined; said means responsive to said difference frequency including means for converting said difference frequency into a first square wave of the same frequency; means for generating a second square wave of the same frequency as said first square wave and with a substantially constant interval between pulses, which interval is substantially equal to the pulse width of said first square wave at said predetermined dewpoint, the leading edges of said first square wave pulses coinciding with the trailing edges of said second square wave pulses; and an AND gate fed by said first and second square waves to indicate by the nonconduction or conduction thereof the dry or wet condition, respectively, of the gas being monitored.
Claim 2
Dependent Claim
234 words
A dewpoint monitor for gases comprising: a first oscillator; means responsive to humidity for controlling the frequency of the output of said first oscillator; means subjecting said responsive means to contact with a gas being monitored; a second oscillator having a substantially constant frequency output; means for mixing said oscillator outputs to secure the difference frequency therebetween; means for indicating a dry condition of the gas being monitored below a predetermined dewpoint; means for indicating a wet condition of the gas being monitored above said predetermined dewpoint; means responsive to said difference frequency for determining whether the gas being monitored is in a dry or wet condition and for actuating the appropriate indicating means for the condition determined; said means responsive to said difference frequency including means for converting said difference frequency into a first square wave of the same frequency; means for generating a second square wave of the same frequency as said first square wave and with a substantially constant interval between pulses, which interval is substantially equal to the pulse width of said first square wave at said predetermined dewpoint, the leading edges of said first square wave pulses coinciding with the trailing edges of said second square wave pulses; and an AND gate fed by said first and second square waves to indicate by the nonconduction or conduction thereof the dry or wet condition, respectively, of the gas being monitored.
Claim 3
Dependent Claim
64 words
The dewpoint monitor defined in claim 1 in which: said means for generating the second square wave is a one shot multivibrator whose pulse is terminated by the leading edge of the pulse of the first square wave; and means for adjusting said multivibrator circuit to adjust its interval between pulses to the width of the first square wave pulse at said predetermined dewpoint.
Claim 4
Dependent Claim
64 words
The dewpoint monitor defined in claim 1 in which: the widths of the first and second square wave pulses and their frequency change with change in the difference frequency while the interval between pulses of said second square wave remains constant, so that at dewpoints above said predetermined dewpoint the pulses of said square waves overlap to produce an output from said AND gate.
Claim 5
Dependent Claim
34 words
The dewpoint monitor defined in claim 1 including: an integrator fed by said AND gate; and means responsive to a predetermined amplitude of the output from said integrator for actuating the appropriate indicating means.
Claim 6
Dependent Claim
49 words
The dewpoint monitor defined in claim 4 including: an invertor fed by said amplitude responsive means, and means for actuating said means for indicating the dry condition of the gas being monitored when said integrator output amplitude is less than said predetermined amplitude and said invertor has an output.
Claim 7
Dependent Claim
40 words
The dewpoint monitor defined in claim 5 including: means for actuating said means for indicating the wet condition of the gas being monitored when said integrator output amplitude is greater than said predetermined amplitude and said invertor has no output.
Claim 8
Dependent Claim
47 words
The dewpoint monitor defined in claim 6 including: a NAN gate; a pulse generating clock; means feeding the outputs of said invertor and said clock to said NAN gate; and means actuating said wet condition indicating means by the intermittent NAN gate output between said clock pulses.
Claim 9
Dependent Claim
148 words
A humidity sensor comprising: a first oscillator; means responsive to humidity for controlling the frequency of the output of said first oscillator; means subjecting said responsive means to contact with a gas being monitored; a second oscillator having a substantially constant frequency output; meaNs for mixing said oscillator outputs to secure the difference therebetween; means for converting said difference frequency into a first square wave of the same frequency; means for generating a second square wave of the same frequency as said first square wave and with a substantially constant interval between pulses, which interval is substantially equal to the pulse width of said first square wave at a predetermined dewpoint of the gas being monitored; and means responsive to overlap and nonoverlap of said first and second square wave pulses to indicate the wet or dry condition of the gas being monitored relative to said predetermined dewpoint.
Claim 10
Dependent Claim
148 words
A humidity sensor comprising: a first oscillator; means responsive to humidity for controlling the frequency of the output of said first oscillator; means subjecting said responsive means to contact with a gas being monitored; a second oscillator having a substantially constant frequency output; meaNs for mixing said oscillator outputs to secure the difference therebetween; means for converting said difference frequency into a first square wave of the same frequency; means for generating a second square wave of the same frequency as said first square wave and with a substantially constant interval between pulses, which interval is substantially equal to the pulse width of said first square wave at a predetermined dewpoint of the gas being monitored; and means responsive to overlap and nonoverlap of said first and second square wave pulses to indicate the wet or dry condition of the gas being monitored relative to said predetermined dewpoint.
Claim 11
Dependent Claim
64 words
The humidity sensor defined in claim 8 in which said last mentioned means includes: an AND gate fed by said first and second square waves; an integrator fed by the output of said AND gate; a threshold detector fed by said integrator; and means responsive to the reaching or nonreaching of the threshold of the detector for actuating the wet or dry condition indication.
References Cited (Backward Citations)
US2536111A
Cited
US2593204A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-09-05 | 1976-03-06 | 1976-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-05 | 1980-03-06 | 1980-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-05 | 1984-03-06 | 1984-09-05 | $7700.00 | Window Closed / Lapsed |