Patent US4651571A successfully refreshed from Google Patents.
US4651571A
Expired / Lapsed
US
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Strain sensor
Assignee: Fisher Controls International LLC
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Filing: 1985-03-05
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Granted: 1987-03-24
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Expires: 2005-03-05
Abstract
Abstract A strain sensor includes a quartz crystal element 9 having a resonant frequency which is dependent on strain imposed on it. The crystal element 9 is caused to vibrate at its resonant frequency by pulses of light transmitted along an optical fibre 5 from a remote location indicated generally at 1. A signal produced by the vibration at the resonant frequency is taken from electrodes 10 and 12 and amplified at 13 and 14 before being used to switch on and off a switch 15 controlling a light source 16. The output from the light source 16, consisting of flashes of light of a frequency indicative of the strain, is transmitted along a second optical fibre 19 and is detected by a photocell 20. The frequency of the output of photocell 20 is measured at 21 to give the desired measurement of strain and to provide feedback to the drive unit 3 which determines the frequency of the flashes of light produced at 2.
Inventors
- 👤 Stuart M. McGlade
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 02:19
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/80; H04B10/806; H04B10/807; G; G01; G01B; G01B11/00; G01B11/16; G01B7/00; G01B7/16; G01L; G01L1/00; G01L1/16; G01L1/162; G01L1/167
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
152 words
A strain sensor comprising: at a first location optical to electrical transducing means, a sensor element of the type which has a resonant frequency dependent on strain imposed on it, and means for using energy from the transducing means to stimulate vibration of the element, to amplify a signal produced as a result of the vibration and to generate light modulated in accordance with that signal and therefore carrying information indicative of the strain; means for transmitting the modulated light carrying this information to a second location; at the second location means for receiving this modulated light carrying information indicative of strain, and a pulsed light source which causes the transducing means at the first location to produce pulses of voltage within a frequency band chosen to stimulate the said vibration; and means for transmitting light from the light source at the second location to the transducing means at the first location.
Claim 2
Dependent Claim
152 words
A strain sensor comprising: at a first location optical to electrical transducing means, a sensor element of the type which has a resonant frequency dependent on strain imposed on it, and means for using energy from the transducing means to stimulate vibration of the element, to amplify a signal produced as a result of the vibration and to generate light modulated in accordance with that signal and therefore carrying information indicative of the strain; means for transmitting the modulated light carrying this information to a second location; at the second location means for receiving this modulated light carrying information indicative of strain, and a pulsed light source which causes the transducing means at the first location to produce pulses of voltage within a frequency band chosen to stimulate the said vibration; and means for transmitting light from the light source at the second location to the transducing means at the first location.
Claim 3
Dependent Claim
43 words
A strain sensor according to claim 1 in which the sensor element is piezoelectric, is arranged to be stimulated into vibration by electric energy from the transducing means and is arranged to generate an electric signal as a result of the said vibration.
Claim 4
Dependent Claim
17 words
A strain sensor according to claim 1 including a transformer for increasing the voltage of the pulses.
Claim 5
Dependent Claim
37 words
A strain sensor according to claim 3, including a feedback arrangement at the second location arranged to use the optical signal returned from the first location to control the pulse repetition frequency of the source of light.
Claim 6
Dependent Claim
37 words
A strain sensor according to claim 1, including a feedback arrangement at the second location arranged to use the optical signal returned from the first location to control the pulse repetition frequency of the source of light.
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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) | 1990-03-23 | 1990-09-22 | 1991-03-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-23 | 1994-09-22 | 1995-03-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-23 | 1998-09-22 | 1999-03-24 | $7700.00 | Window Closed / Lapsed |