US4656871A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitor sensor and method
Assignee: Motorola Solutions Inc
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Filing: 1985-07-16
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Granted: 1987-04-14
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Expires: 2005-07-16
Abstract
Abstract A method and apparatus are described for converting variations in a measured variable (such as pressure) to corresponding variations in an electrical output signal. The preferred method utilizes a capacitive sensor whose capacitance changes to reflect changes in the measured variable. The changes in capacitance are preferably used to vary the gain of a switched-capacitor amplifier whose signal input receives a relatively constant DC reference voltage. The amplifiers' output may be sampled and further amplified to provide an output signal which is indicative of the value of the measured variable.
Inventors
- 👤 Walter S. Czarnocki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 05:51
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/12; G01D5/14; G01D5/24; G01L; G01L9/00; G01L9/12; H; H03; H03F; H03F1/00; H03F1/30; H03F1/303
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
124 words
A method of converting a measured input variable to an electrical output signal, comprising: (a) converting changes in the variable to changes in capacitance; (b) providing a DC reference signal having a substantially constant value; (c) multiplying the DC reference signal by a variable gain which changes as a function of changes in said capacitance, including providing an amplifier connected to form part of a switched-capacitor amplifier with said capacitance, coupling the capacitance in a feedback path around the amplifier so as to vary the gain of the amplifier in accordance with variations in the capacitance, and applying the reference signal to the amplifier's input; and (d) outputting the multiplied reference signal for use as an indicator of the value of the input variable.
Claim 2
Independent Claim
124 words
A method of converting a measured input variable to an electrical output signal, comprising: (a) converting changes in the variable to changes in capacitance; (b) providing a DC reference signal having a substantially constant value; (c) multiplying the DC reference signal by a variable gain which changes as a function of changes in said capacitance, including providing an amplifier connected to form part of a switched-capacitor amplifier with said capacitance, coupling the capacitance in a feedback path around the amplifier so as to vary the gain of the amplifier in accordance with variations in the capacitance, and applying the reference signal to the amplifier's input; and (d) outputting the multiplied reference signal for use as an indicator of the value of the input variable.
Claim 3
Independent Claim
17 words
A method as set forth in claim wherein step (d) includes sampling the multiplied DC reference signal.
Claim 4
Dependent Claim
17 words
A method as set forth in claim 2 wherein step (d) further includes amplifying the sampled signal.
Claim 5
Dependent Claim
30 words
A method as set forth in claim 1 wherein the measured input variable is pressure, and wherein step (a) includes converting changes in the meausred pressure to changes in capacitance.
Claim 6
Dependent Claim
141 words
A capacitive pressure sensor, comprising: a sensor capacitance for sensing pressure and for varying the value of capacitance in response to changes in the value of the measured pressure; a switched-capacitor amplifier having an input and an output; means coupling the sensor capacitance in a feedback configuration between the amplifier's input and output such that the amplifier's gain changes in response to changes in the value of the sensor capacitance; means for developing a reference voltage having a substantially constant value; means for coupling the reference voltage to the input of the amplifier such that the amplifier's output includes a signal whose value corresponds to the value of the reference voltage times the gain of the amplifier; and means receiving the signal at the output of the amplifier to develop a further signal whose value is indicative of the sensed pressure.
Claim 7
Dependent Claim
141 words
A capacitive pressure sensor, comprising: a sensor capacitance for sensing pressure and for varying the value of capacitance in response to changes in the value of the measured pressure; a switched-capacitor amplifier having an input and an output; means coupling the sensor capacitance in a feedback configuration between the amplifier's input and output such that the amplifier's gain changes in response to changes in the value of the sensor capacitance; means for developing a reference voltage having a substantially constant value; means for coupling the reference voltage to the input of the amplifier such that the amplifier's output includes a signal whose value corresponds to the value of the reference voltage times the gain of the amplifier; and means receiving the signal at the output of the amplifier to develop a further signal whose value is indicative of the sensed pressure.
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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) | 1990-04-13 | 1990-10-13 | 1991-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-13 | 1994-10-13 | 1995-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-13 | 1998-10-13 | 1999-04-14 | $7700.00 | Window Closed / Lapsed |