Patent US5796745A successfully refreshed from Google Patents.
Patent US5739416A successfully refreshed from Google Patents.
US5739416A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fast, high sensitivity dewpoint hygrometer
Assignee: California Institute of Technology
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Filing: 1996-09-18
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Granted: 1998-04-14
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Expires: 2016-09-18
Abstract
Abstract A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature. The effect of this response is to heat or cool the surface moisture-sensitive device, which shifts the equilibrium with respect to evaporation and condensation at the surface of the device. The equilibrium temperature under feedback control is a measure of dewpoint or frostpoint.
Inventors
- 👤 Michael E. Hoenk
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:35
CPC Classifications
G; G01; G01N; G01N25/00; G01N25/56; G01N25/66; G01N25/68
Claims Analysis
Total Claims: 60
Claim 1
Independent Claim
200 words
A device for measuring humidity, comprising: (a) an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) a temperature regulating device, proximate to the resonant moisture-sensitive device, for controlling the temperature of the resonant moisture-sensitive device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant moisture-sensitive device by governing the temperature regulating device used for controlling the temperature of the resonant moisture-sensitive device; (d) a temperature sensor, proximate the resonant moisture-sensitive device, for measuring the temperature of the resonant moisture-sensitive device and generating an output signal indicative of the amount of moisture in the gas.
Claim 2
Independent Claim
200 words
A device for measuring humidity, comprising: (a) an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) a temperature regulating device, proximate to the resonant moisture-sensitive device, for controlling the temperature of the resonant moisture-sensitive device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant moisture-sensitive device by governing the temperature regulating device used for controlling the temperature of the resonant moisture-sensitive device; (d) a temperature sensor, proximate the resonant moisture-sensitive device, for measuring the temperature of the resonant moisture-sensitive device and generating an output signal indicative of the amount of moisture in the gas.
Claim 3
Dependent Claim
48 words
The device of claim 1, wherein the temperature sensor is coupled to the controller, and wherein the controller is further for correcting the feedback signal in response to the measured temperature of the resonant moisture-sensitive device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 4
Dependent Claim
64 words
The device of claim 1, wherein the temperature sensor comprises: (a) a resistor; (b) a current source, coupled to the resistor, for supplying a constant current flow through the resistor; (c) a voltage-sensing circuit, coupled across the resistor, for measuring voltage across the resistor from current flowing through the resistor, such voltage varying with temperature, and for generating a signal indicative of such temperature.
Claim 5
Dependent Claim
19 words
The device of claim 1, wherein the condensation-dependent signal indicates a change in frequency of the RF oscillator circuit.
Claim 6
Dependent Claim
19 words
The device of claim 1, wherein the condensation-dependent signal indicates a change in amplitude of the RF oscillator circuit.
Claim 7
Dependent Claim
19 words
The device of claim 1, wherein the condensation-dependent signal indicates a change in phase of the RF oscillator circuit.
Claim 8
Dependent Claim
14 words
The device of claim 1, wherein the temperature regulating device is a thermoelectric cooler.
Claim 9
Dependent Claim
47 words
The device of claim 1, wherein the condensation-dependent signal has an analog form, and further including a signal conditioning circuit coupled to the output of the RF oscillator circuit and to an input to the controller, for converting the condensation-dependent signal from analog form to digital form.
Claim 10
Dependent Claim
42 words
The device of claim 1, further including means for periodically elevating the temperature of the resonant moisture-sensitive device above the dewpoint and measuring the condensation-dependent signal at such elevated temperature to provide a reference level signal for the device for measuring humidity.
Claim 11
Dependent Claim
17 words
The device of claim 1, wherein the resonant moisture-sensitive device is a resonant surface acoustic wave device.
Claim 12
Dependent Claim
15 words
The device of claim 1, wherein the resonant moisture-sensitive device has a high Q value.
Claim 13
Dependent Claim
12 words
The device of claim 11, wherein the Q value exceeds about 2,000.
Claim 14
Independent Claim
219 words
A device for measuring humidity, comprising: (a) an RF oscillator circuit, including a resonant surface acoustic wave device having a high Q value and a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant surface acoustic wave device; (b) a temperature regulating device, proximate to the resonant surface acoustic wave device, for controlling the temperature of the resonant surface acoustic wave device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant surface acoustic wave device by governing the temperature regulating device used for controlling the temperature of the resonant surface acoustic wave device; (d) a temperature sensor, proximate the resonant surface acoustic wave device, for measuring the temperature of the resonant surface acoustic wave device and generating an output signal indicative of the amount of moisture in the gas.
Claim 15
Independent Claim
219 words
A device for measuring humidity, comprising: (a) an RF oscillator circuit, including a resonant surface acoustic wave device having a high Q value and a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant surface acoustic wave device; (b) a temperature regulating device, proximate to the resonant surface acoustic wave device, for controlling the temperature of the resonant surface acoustic wave device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant surface acoustic wave device by governing the temperature regulating device used for controlling the temperature of the resonant surface acoustic wave device; (d) a temperature sensor, proximate the resonant surface acoustic wave device, for measuring the temperature of the resonant surface acoustic wave device and generating an output signal indicative of the amount of moisture in the gas.
Claim 16
Dependent Claim
50 words
The device of claim 13, wherein the temperature sensor is coupled to the controller, and wherein the controller is further for correcting the feedback signal in response to the measured temperature of the resonant surface acoustic wave device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 17
Dependent Claim
64 words
The device of claim 13, wherein the temperature sensor comprises: (a) a resistor: (b) a current source, coupled to the resistor, for supplying a constant current flow through the resistor; (c) a voltage-sensing circuit, coupled across the resistor, for measuring voltage across the resistor from current flowing through the resistor, such voltage varying with temperature, and for generating a signal indicative of such temperature.
Claim 18
Dependent Claim
19 words
The device of claim 13, wherein the condensation-dependent signal indicates a change in frequency of the RF oscillator circuit.
Claim 19
Dependent Claim
19 words
The device of claim 13, wherein the condensation-dependent signal indicates a change in amplitude of the RF oscillator circuit.
Claim 20
Dependent Claim
19 words
The device of claim 13, wherein the condensation-dependent signal indicates a change in phase of the RF oscillator circuit.
Claim 21
Dependent Claim
14 words
The device of claim 13, wherein the temperature regulating device is a thermoelectric cooler.
Claim 22
Dependent Claim
47 words
The device of claim 13, wherein the condensation-dependent signal has an analog form, and further including a signal conditioning circuit coupled to the output of the RF oscillator circuit and to an input to the controller, for converting the condensation-dependent signal from analog form to digital form.
Claim 23
Dependent Claim
44 words
The device of claim 13, further including means for periodically elevating the temperature of the resonant surface acoustic wave device above the dewpoint and measuring the condensation-dependent signal at such elevated temperature to provide a reference level signal for the device for measuring humidity.
Claim 24
Dependent Claim
19 words
The device of claim 13, wherein the Q value of the resonant surface acoustic wave device exceeds about 2,000.
Claim 25
Dependent Claim
249 words
An electronic hygrometer comprising: (a) an RF oscillator circuit, including a resonant surface acoustic wave device having a high Q value and a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal directly dependent on the amount of condensation on the surface of the resonant surface acoustic wave device; (b) a thermoelectric cooler, proximate to the resonant surface acoustic wave device, for controlling the temperature of the resonant surface acoustic wave device; (c) a temperature sensor, proximate the resonant surface acoustic wave device, for measuring the temperature of the resonant surface acoustic wave device and for generating an output signal indicative of the amount of moisture in the gas; (d) a controller, coupled to the output of the RF oscillator circuit, the thermoelectric cooler, and the temperature sensor, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant surface acoustic wave device by governing the thermoelectric cooler used for controlling the temperature of the resonant surface acoustic wave device; and (3) correcting the feedback signal in response to the measured temperature of the resonant surface acoustic wave device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 26
Dependent Claim
249 words
An electronic hygrometer comprising: (a) an RF oscillator circuit, including a resonant surface acoustic wave device having a high Q value and a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation from the gas onto the surface, the RF oscillator circuit being configured to generate a condensation-dependent signal directly dependent on the amount of condensation on the surface of the resonant surface acoustic wave device; (b) a thermoelectric cooler, proximate to the resonant surface acoustic wave device, for controlling the temperature of the resonant surface acoustic wave device; (c) a temperature sensor, proximate the resonant surface acoustic wave device, for measuring the temperature of the resonant surface acoustic wave device and for generating an output signal indicative of the amount of moisture in the gas; (d) a controller, coupled to the output of the RF oscillator circuit, the thermoelectric cooler, and the temperature sensor, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant surface acoustic wave device by governing the thermoelectric cooler used for controlling the temperature of the resonant surface acoustic wave device; and (3) correcting the feedback signal in response to the measured temperature of the resonant surface acoustic wave device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 27
Dependent Claim
48 words
The electronic hygrometer of claim 23, wherein the condensation-dependent signal has an analog form, and further including a signal conditioning circuit coupled to the output of the RF oscillator circuit and to an input to the controller, for converting the condensation-dependent signal from analog form to digital form.
Claim 28
Dependent Claim
43 words
The electronic hygrometer of claim 23, further including means for periodically elevating the temperature of the resonant surface acoustic wave device above the dewpoint and measuring the condensation-dependent signal at such elevated temperature to provide a reference level signal for the electronic hygrometer.
Claim 29
Independent Claim
169 words
A device responsive to changes in humidity, comprising: (a) an RF oscillator circuit, including an oscillator circuit and a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) a temperature regulating device, proximate to the resonant moisture-sensitive device, for controlling the temperature of the resonant moisture-sensitive device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant moisture-sensitive device by governing the temperature regulating device used for controlling the temperature of the resonant moisture-sensitive device.
Claim 30
Independent Claim
169 words
A device responsive to changes in humidity, comprising: (a) an RF oscillator circuit, including an oscillator circuit and a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, configured to generate a condensation-dependent signal indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) a temperature regulating device, proximate to the resonant moisture-sensitive device, for controlling the temperature of the resonant moisture-sensitive device; (c) a controller, coupled to the output of the RF oscillator circuit and to the temperature regulating device, for: (1) monitoring the condensation-dependent signal of the RF oscillator circuit; and (2) generating a feedback signal to the temperature regulating device responsive to changes in the condensation-dependent signal relative to a set point, the feedback signal controlling the amount of condensation on the resonant moisture-sensitive device by governing the temperature regulating device used for controlling the temperature of the resonant moisture-sensitive device.
Claim 31
Dependent Claim
22 words
The device of claim 26, wherein the resonant moisture-sensitive device is a resonant surface acoustic wave device having a characteristic Q value.
Claim 32
Dependent Claim
19 words
The device of claim 27, wherein the Q value of the resonant surface acoustic wave device exceeds about 2,000.
Claim 33
Dependent Claim
15 words
The device of claim 26, wherein the resonant moisture-sensitive device has a high Q value.
Claim 34
Dependent Claim
17 words
The device of claim 29, wherein the Q value of the resonant moisture-sensitive device exceeds about 2,000.
Claim 35
Independent Claim
160 words
A method for measuring humidity, comprising the steps of: (a) measuring a condensation-dependent signal output by an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the condensation-dependent signal being indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) monitoring the condensation-dependent signal of the RF oscillator circuit; (c) comparing changes in the condensation-dependent signal relative to a set point; (d) regulating the temperature of the resonant moisture-sensitive device in response to such changes so as to maintain equilibrium at the surface of the resonant moisture-sensitive device between moisture in the gas and moisture condensed on the surface of the resonant moisture-sensitive device; (e) measuring the temperature of the moisture-sensitive device; (f) generating an output signal, indicative of the amount of moisture in the gas, from the measured temperature.
Claim 36
Independent Claim
160 words
A method for measuring humidity, comprising the steps of: (a) measuring a condensation-dependent signal output by an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the condensation-dependent signal being indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) monitoring the condensation-dependent signal of the RF oscillator circuit; (c) comparing changes in the condensation-dependent signal relative to a set point; (d) regulating the temperature of the resonant moisture-sensitive device in response to such changes so as to maintain equilibrium at the surface of the resonant moisture-sensitive device between moisture in the gas and moisture condensed on the surface of the resonant moisture-sensitive device; (e) measuring the temperature of the moisture-sensitive device; (f) generating an output signal, indicative of the amount of moisture in the gas, from the measured temperature.
Claim 37
Dependent Claim
44 words
The method of claim 31, further comprising the step of: (a) correcting regulation of the temperature of the resonant moisture-sensitive device in response to the measured temperature of the resonant moisture-sensitive device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 38
Dependent Claim
19 words
The method of claim 31, wherein the condensation-dependent signal indicates a change in frequency of the RF oscillator circuit.
Claim 39
Dependent Claim
19 words
The method of claim 31, wherein the condensation-dependent signal indicates a change in amplitude of the RF oscillator circuit.
Claim 40
Dependent Claim
19 words
The method of claim 31, wherein the condensation-dependent signal indicates a change in phase of the RF oscillator circuit.
Claim 41
Dependent Claim
29 words
The method of claim 31, wherein the condensation-dependent signal has an analog form, and further including the step of converting the condensation-dependent signal from analog form to digital form.
Claim 42
Dependent Claim
39 words
The method of claim 31, further including the steps of: (a) periodically elevating the temperature of the resonant moisture-sensitive device above the dewpoint; and (b) measuring the condensation-dependent signal at such elevated temperature to provide a reference level signal.
Claim 43
Dependent Claim
22 words
The method of claim 31, wherein the resonant moisture-sensitive device is a resonant surface acoustic wave device having a characteristic Q value.
Claim 44
Dependent Claim
19 words
The method of claim 38, wherein the Q value of the resonant surface acoustic wave device exceeds about 2,000.
Claim 45
Dependent Claim
15 words
The method of claim 31, wherein the resonant moisture-sensitive device has a high Q value.
Claim 46
Dependent Claim
12 words
The method of claim 40, wherein the Q value exceeds about 2,000.
Claim 47
Dependent Claim
19 words
The method of claim 31, wherein the output signal is the temperature of the resonant moisture-sensitive device at equilibrium.
Claim 48
Independent Claim
153 words
A method for measuring humidity, comprising the steps of: (a) measuring a condensation-dependent signal output by an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the condensation-dependent signal being indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) monitoring the condensation-dependent signal of the RF oscillator circuit; (c) comparing changes in the condensation-dependent signal relative to a set point; (d) regulating the temperature of the resonant moisture-sensitive device in response to such changes so as to maintain the condensation-dependent signal nearly constant over time in the presence of time-varying moisture in the gas; (e) measuring the temperature of the resonant moisture-sensitive device; and (f) generating an output signal, indicative of the amount of moisture in the gas, from the measured temperature.
Claim 49
Independent Claim
153 words
A method for measuring humidity, comprising the steps of: (a) measuring a condensation-dependent signal output by an RF oscillator circuit including a resonant moisture-sensitive device having a surface that is essentially non-hygroscopic, sensitive to moisture in an ambient gas and subject to condensation of moisture from the gas onto the surface, the condensation-dependent signal being indicative of the amount of condensation on the surface of the resonant moisture-sensitive device; (b) monitoring the condensation-dependent signal of the RF oscillator circuit; (c) comparing changes in the condensation-dependent signal relative to a set point; (d) regulating the temperature of the resonant moisture-sensitive device in response to such changes so as to maintain the condensation-dependent signal nearly constant over time in the presence of time-varying moisture in the gas; (e) measuring the temperature of the resonant moisture-sensitive device; and (f) generating an output signal, indicative of the amount of moisture in the gas, from the measured temperature.
Claim 50
Dependent Claim
44 words
The method of claim 43, further comprising the step of: (a) correcting regulation of the temperature of the resonant moisture-sensitive device in response to the measured temperature of the resonant moisture-sensitive device so as to substantially remove a temperature-dependent component from the condensation-dependent signal.
Claim 51
Dependent Claim
19 words
The method of claim 43, wherein the condensation-dependent signal indicates a change in frequency of the RF oscillator circuit.
Claim 52
Dependent Claim
19 words
The method of claim 43, wherein the condensation-dependent signal indicates a change in amplitude of the RF oscillator circuit.
Claim 53
Dependent Claim
19 words
The method of claim 43, wherein the condensation-dependent signal indicates a change in phase of the RF oscillator circuit.
Claim 54
Dependent Claim
29 words
The method of claim 43, wherein the condensation-dependent signal has an analog form, and further including the step of converting the condensation-dependent signal from analog form to digital form.
Claim 55
Dependent Claim
39 words
The method of claim 43, further including the steps of: (a) periodically elevating the temperature of the resonant moisture-sensitive device above the dewpoint; and (b) measuring the condensation-dependent signal at such elevated temperature to provide a reference level signal.
Claim 56
Dependent Claim
22 words
The method of claim 43, wherein the resonant moisture-sensitive device is a resonant surface acoustic wave device having a characteristic Q value.
Claim 57
Dependent Claim
19 words
The method of claim 50, wherein the Q value of the resonant surface acoustic wave device exceeds about 2,000.
Claim 58
Dependent Claim
15 words
The method of claim 43, wherein the resonant moisture-sensitive device has a high Q value.
Claim 59
Dependent Claim
12 words
The method of claim 52, wherein the Q value exceeds about 2,000.
Claim 60
Dependent Claim
24 words
The method of claim 43, wherein the output signal is the temperature of the resonant moisture-sensitive device when the condensation-dependent signal is nearly constant.
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| 3.5 Years (Year 4) | 2001-04-13 | 2001-10-13 | 2002-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-04-13 | 2005-10-13 | 2006-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-04-13 | 2009-10-13 | 2010-04-14 | $7700.00 | Window Closed / Lapsed |