GB2146123A - Apparatus for monitoring displacement - Google Patents
Apparatus for monitoring displacement Download PDFInfo
- Publication number
- GB2146123A GB2146123A GB08419491A GB8419491A GB2146123A GB 2146123 A GB2146123 A GB 2146123A GB 08419491 A GB08419491 A GB 08419491A GB 8419491 A GB8419491 A GB 8419491A GB 2146123 A GB2146123 A GB 2146123A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cavity
- frequency
- displacement
- monitoring
- electromagnetic radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000006073 displacement reaction Methods 0.000 title claims abstract description 36
- 238000012544 monitoring process Methods 0.000 title claims abstract description 28
- 239000013307 optical fiber Substances 0.000 claims abstract description 21
- 230000003287 optical effect Effects 0.000 claims abstract description 18
- 230000005670 electromagnetic radiation Effects 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 10
- 230000001419 dependent effect Effects 0.000 claims description 12
- 230000005855 radiation Effects 0.000 claims description 7
- 239000000835 fiber Substances 0.000 claims description 5
- 230000005611 electricity Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000006229 carbon black Substances 0.000 description 2
- 208000032365 Electromagnetic interference Diseases 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000002828 fuel tank Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
- G01L1/162—Measuring force or stress, in general using properties of piezoelectric devices using piezoelectric resonators
- G01L1/167—Measuring force or stress, in general using properties of piezoelectric devices using piezoelectric resonators optical excitation or measuring of vibrations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
- G01F23/16—Indicating, recording, or alarm devices being actuated by mechanical or fluid means, e.g. using gas, mercury, or a diaphragm as transmitting element, or by a column of liquid
- G01F23/164—Indicating, recording, or alarm devices being actuated by mechanical or fluid means, e.g. using gas, mercury, or a diaphragm as transmitting element, or by a column of liquid using a diaphragm, bellow as transmitting element
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/04—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by acoustic means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0001—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
- G01L9/0008—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using vibrations
- G01L9/0022—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using vibrations of a piezoelectric element
- G01L9/0023—Optical excitation or measuring
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Acoustics & Sound (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
A member 4 is arranged so that its displacement controls the position of a piston 3 in a cylinder 1 having a gas-filled cavity 2. The cylinder 1 contains a block 8 of material which, when illuminated with pulses of electromagnetic radiation from a light source 6, generates pulses of acoustic energy, causing vibration of the gas within the cavity 2. The frequency of the vibration depends upon the frequency of the pulses of incident electromagnetic radiation and the resonant frequency of the cavity 2, which in turn depends upon its dimensions. Hence by monitoring the frequency of the vibration, the displacement of the member 4 may be found. The frequency of the vibration may be determined using an optical interferometer comprising two optical fibres 11 and 12 connected in parallel and combined at a return optical fibre 13. A feedback loop may be provided via amplitude detector 15 to cause the frequency of pulse generator 5 to approach the resonance frequency of the cavity, and the member 4 may be brought to a desired position by the feedback loop including hydraulic control circuit 19 and actuator 17. <IMAGE>
Description
SPECIFICATION
Apparatus for monitoring displacement
This invention relates to apparatus for monitoring displacement. It arose as a result of an
endeavour to find an entirely new method of
sensing displacements which would be supe
rior to known techniques in at least some
specialised circumstances. Considerations
which the inventor particularly had in mind were the need for simplicity, robustness and
reliability and the need to avoid the use of
electricity in some environments, e.g. where there is a fire risk or the possibility of electro
magnetic interference.
The invention provides apparatus for monitoring displacement comprising a cavity hav
ing a resonant frequency dependent upon the displacement, photo-acoustic means arranged to cause resonation of gas within the cavity, and monitoring means for monitoring the fre
quency of resonation, this being related to the said displacement.
The photo-acoustic means is a facility em
ploying the known process whereby acoustic energy is generated when certain materials are illuminated by one or more pulses of light.
In this specification, "light" and "optical" is to be construed as including all electromagnetic radiation (i.e. infra-red, visible or ultraviolet radiation), and the term "acoustic" should be taken to include ultra-sonic, audible, and sub-sonic frequencies.
More particularly, the invention provides apparatus for monitoring displacement comprising: a cavity having a resonant frequency which is dependent upon the displacement; a material which generates acoustic energy when electromagnetic radiation is incident upon it, the said material bring associated with the cavity in such a way that the acoustic energy causes gas within the cavity to vibrate; illuminating means for illuminating the material with at least one pulse of electromagnetic radiation; and monitoring means for monitoring the resulting vibration of the gas within the cavity.
If, as is preferred, the monitoring means is constituted by an optical acoustic sensor, i.e.
an optical microphone, the need for electricity in the environment of the displacement to be monitored can be entirely eliminated. Also, as will become apparent from the following description, it is possible to build a sensor in accordance with the invention which is particularly simple, robust and reliable as compared, for example, with a conventional optical position encoder which is a delicate instrument requiring precision manufacturing techniques and alignment. The material which generates the acoustic energy when the radiation is incident could be contained within the cavity, form part of the cavity, or be arranged outside the cavity. In the latter case an aperture or diaphragm could be provided to give
access to the cavity for the acoustic energy.
The idea of using an optical microphone in this context is in itself a novel concept and could be empioyed in apparatus which uses
non-photo-acoustic means for causing resonation of the cavity. Accordingly, a further as
pect of the invention provides apparatus for
monitoring displacement comprising: a cavity
having a resonant frequency which is dependent upon the displacement; means for causing gas within the cavity to vibrate; and an optical microphone for monitoring the result- ing vibration of the gas within the cavity.
It could be possible to use just a single pulse of optical energy to cause the vibration of gas within the cavity at its resonant frequency, in which case that frequency can be used as a measure of the displacement to be monitored. It is better, however, to use a train of pulses of optical energy and to tune the frequency of these until the amplitude of the vibrations of the gas within the cavity is at a maximum. The pulses of optical energy can then be assumed to have the same frequency as the resonant frequency of the cavity, this being a measure of the displacement. Another technique which, though not preferred, would be possible, is to use pulses of light at a fixed frequency. The amplitude of the resulting vibration will then be dependent upon the closeness of the resonant frequency of the cavity to the frequency of the light pulses.This amplitude can thus be used as a crude measure of the resonant frequency.
Displacement of a member may be monitored to provide a measure of its position, or to provide an indication of whether it is to one side or the other side of a desired position to which it is to be moved.
In one preferred form of the invention, the monitoring means includes an optical fibre located within the cavity, means for passing electromagnetic radiation along it, and means for detecting the electromagnetic radiation after passing along it. Acoustic energy impinging on the optical fibre causes its transmissive properties to vary and so the radiation detected after passing along the fibre is phase modulated at a frequency and by an amplitude dependent upon the frequency and amplitude of the acoustic energy to which it is exposed.
In this preferred form of the invention the monitoring means preferably also includes a second optical fibre located outside the cavity, the first and second optical fibres being arranged in parallel to receive electromagnetic radiation from the same source. The radiation phase modulation after passing along the first fibre, is combined with the radiation after passing along the second fibre so as to produce an amplitude modulated signal on a third optical fibre. The first, second and third optical fibres can be considered to constitute an optical interferometer. The refractive index of the first optical fibre changes when acoustic energy is incident upon it, and hence the velocity of light travelling along it also changes.Thus the phase of light transmitted along the second optical fibre, which being outside the cavity is unaffected by the acoustic energy, is different from that which passes along the first optical fibre, the difference depending upon the amount of acoustic energy generated within the cavity. Observations of variations in the amplitude of light carried by the third optical fibre enables the frequency of the vibration to be determined.
It is preferred that the cavity has dimensions which are dependent upon the displacement of a member which it is desired to monitor. Hence its displacement determines the resonant frequency of the cavity.
Preferably means are included for using the frequency of the resulting vibration of the gas within the cavity to control the movement of a member from its actual position to a desired position.
The invention is now further described by way of example with reference to the accompanying drawings, in which:
Figure 1 schematically illustrates one apparatus in accordance with the invention; and
Figure 2 schematically illustrates another apparatus in accordance with the invention, like references being used for like parts throughout.
With reference to Figure 1, a hollow cylinder 1 has a gas-filled cavity 2, the dimensions of which can be varied by the movement of a piston 3. The piston 3 is arranged to move with a member 4, the displacement of which it is desired to monitor.
A pulse generator 5 controls a laser diode 6 to produce pulsed monochromatic light which is transmitted via a long first optical fibre 7 to the cylinder 1 and into the cavity 2, where it is incident upon a block 8 of carbon black positioned within the cavity 2. Carbon black has photo-acoustic properties such that incident light is absorbed by it and causes thermal energy to be generated, which in turn causes the gas within the cavity to expand and rarify, hence generating acoustic energy.
Since the light is pulsed, the acoustic energy is also pulsed, being emitted only when light is incident upon the block 8. The frequency of the acoustic pulses is dependent, not only on the frequency of the light pulses, but also on the resonant frequency of the cavity 1, and hence the position of the member 4. The amplitude of vibration of the cavity caused by the pulses of acoustic energy is greatest when the frequency of the light pulses and the resonant frequency coincide.
The frequency of the vibration, and hence the position of the member 4, is monitored by an optical interferometer. Light from a source 9 is sent along a second optical fibre 10 which branches into first and second branches 11 and 1 2 at the cylinder 1. The first branch 11 constitutes a reference path and is located outside the cylinder 1. The second branch 1 2 passes into the cavity 2 and joins with the first branch 11 at a return optical fibre 1 3.
Light passes through the first and second branches 11 and 1 2 and along the return optical fibre 1 3 to a light detector 14, at a location remote from the cylinder 1. Acoustic energy incident upon the second branch 1 2 causes its transmission properties to alter, and hence the velocity of light travelling along it is different to that passing along the first branch 11. When light from the two branches 11 and 1 2 is combined on the return optical fibre 1 3 therefore, there is a phase difference between them due to the effect of the acoustic energy. The amplitude of light on the return optical fibre 1 3 is modulated at a frequency and amplitude according to the vibration of the gas within the cavity.The length of the second branch 1 3 is chosen so that, when the maximum amount of acoustic energy is generated in the cavity 2, a phase shift is introduced which produces the largest degree of amplitude modulation.
The electrical output of the light detector 14 is applied to a peak-to-peak amplitude detector 1 5. This detects the difference between the maximum and minimum amplitude values of the light on the return optical fibre 1 3, and a signal representing this difference, and hence the amplitude of vibration of the gas within the cavity is applied to the pulse generator 5.This signal acts as a control signal to increase the peak-to-peak amplitude detected at 15, and hence bring the frequency of the light pulses applied on optical fibre 1 7 closer to the resonant frequency of the cavity 2:
The frequency of the light pulses on the first optical fibre 7 is displayed at 1 6 and, since this tends towards the resonant frequency of the cavity 2, the displacement of the member 4 can be determined.
A feedback path is also provided to control a hydraulic actuator 1 7 governing the movement of the member 4. A control signal representing a desired position of the member is applied on line 18 to a hydraulic control system 1 9. A signal representing the frequency of the light pulses, and thus the actual position of the member 4, is taken from an output of the pulse generator 5 and applied to the control circuit 19 on line 20. This controls the supply of fluid to a hydraulic line 21 so as to cause the actuator 1 7 to move the member 4 closer to the desired position. In an alternative construction, the hydraulic components 17, 19, 21 could be replaced by pneumatic or optical equivalents.
Since the components 13, 4 and 1 7 do not use electrical energy, they can safely be located in environments where the use of elec tricity, or to which the supply of electricity constitutes a fire hazard. The components 5, 6, 9, 14, 15, 1 6 and 1 9 which do use or produce electricity, can be positioned at a remote location where no such hazard exists.
Although in this embodiment the cavity 2 is cylindrical, it is, of course, possible to employ other configurations.
It will be appreciated that the above illustrated embodiment is only one example of many possible applications for the invention.
For example, in another embodiment of the invention, the cavity is the space defined above a liquid surface in a container such as a fuel tank and changes in the liquid level vary the resonant frequency, thereby giving an indication of the amount of liquid.
With reference to Figure 2, another apparatus is similar to that described above but the output of the light detector 14 is passed to a spectrum analyser 22 rather than the amplitude detector 1 5 which is omitted. The spectrum analyser 22 detects the frequency spectrum of the signal it receives, monitoring the frequency and amplitude of the constituents.
Thus it can detect not only the resonance mode monitored in the previously described embodiment, from which information concerning the displacement of the member 4 is obtained, but also another resonance mode, the frequency of which does not vary with movement of the piston 3. In this case, with the cylindrical cavity 2, suitable modes to monitor are the longitudinal mode to obtain displacement information and the radial mode to obtain a resonant frequency which does not depend on the position of the piston 3. The velocity of sound in the gas filling varies with temperature and humidity, and since the resonant frequency depends on the sound velocity it can lead to inaccuracies in measuring the displacement.However, since the resonant frequencies of both the longitudinal and radial modes are dependent on the velocity of sound, by taking the ratio of them the effects of variations in velocity may be eliminated.
Thus the output of the spectrum analyser 22 is applied to a peak detecting circuit 23 which determines the resonant frequencies of the two resonant modes under consideration, and these are then divided by a divider 14 to obtain the ratio. Any variation of the sound velocity due to changes in ambient conditions does not alter the ratio but the ratio does change in dependence of the displacement of the piston 3. The output of the divider 24 is used to control the pulse generator 5.
The apparatus described above with reference to Figure 2 is one embodiment as now envisaged in accordance with the invention.
Another possibility might be to monitor the resonant frequencies of two resonant modes which both vary with displacement, but by different amounts, and which also vary with the velocity of sound in the gas filling. Thus by taking the ratio, the effects of temperature and humidity changes can be eliminated whilst still obtaining useful information about the displacement.
Claims (11)
1. Apparatus for monitoring displacement comprising: a cavity having a resonant frequency which is dependent upon the displacement; a material which generates acoustic energy when electromagnetic radiation is incident upon it, the said material being associated with the cavity in such a way that the acoustic energy causes gas within the cavity to vibrate; illuminating means for illuminating the material with at least one pulse of electromagnetic radiation; and monitoring means for monitoring the resulting vibration of the gas within the cavity.
2. Apparatus as claimed in claim 1 and wherein the monitoring means monitors the frequency of the resulting vibration.
3. Apparatus as claimed in claim 1 or 2 in which the illuminating means is designed to illuminate the material with pulses of electromagnetic radiation and in which a feedback path from the monitoring means to the illuminating means serves to control the frequency of the pulses so as to maximise the amplitude of the vibration.
4. Apparatus as claimed in claim 3 and wherein the cavity has a second resonant frequency of a different resonance mode than the first mentioned resonant frequency, and the monitoring means includes means for detecting the two resonant frequencies and obtaining a signal representing their ratio and applying it to the illuminating means via the feedback path.
5. Apparatus as claimed in claim 4 and wherein the second resonant frequency is independent of the displacement.
6. Apparatus as claimed in any preceding claim and wherein the monitoring means includes an optical fibre located within the cavity, means for passing electromagnetic radiation along it, and means for detecting the electromagnetic radiation after passing along it.
7. Apparatus as claimed in claim 6 and wherein the monitoring means includes a second optical fibre located outside the cavity, the first and second optical fibres being arranged in parallel to receive electromagnetic radiation from the same source, and means to combine the radiation, phase modulated after passing along the first fibre, with the radiation after passing along the second fibre so as to produce an amplitude modulation signal on a third optical fibre.
8. Apparatus as claimed in any preceding claim and wherein the cavity has dimensions which are dependent upon displacement of a member which it is desired to monitor.
9. Apparatus as claimed in any preceding claim and including means for using the frequency of the resulting vibration of gas within the cavity to control the movement of a member from its actual position to a desired position.
10. Apparatus for montiring displacement comprising: a cavity having a resonant frequency dependent upon the displacement, photo-acoustic means arranged to cause resonation of gas within the cavity, and monitoring means for monitoring the frequency of resonation, this being related to the said displacement.
11. Apparatus for monitoring displacement comprising: a cavity having a resonant frequency which is dependent upon the displacement; means for causing the gas within the cavity to vibrate; and an optical microphone for monitoring the resultant vibration of the cavity.
1 2. Apparatus substantially as described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB838323685A GB8323685D0 (en) | 1983-09-03 | 1983-09-03 | Monitoring displacement |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8419491D0 GB8419491D0 (en) | 1984-09-05 |
| GB2146123A true GB2146123A (en) | 1985-04-11 |
| GB2146123B GB2146123B (en) | 1987-04-23 |
Family
ID=10548309
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838323685A Pending GB8323685D0 (en) | 1983-09-03 | 1983-09-03 | Monitoring displacement |
| GB08327814A Expired GB2146120B (en) | 1983-09-03 | 1983-10-18 | Photoacoustic force sensor |
| GB08419491A Expired GB2146123B (en) | 1983-09-03 | 1984-07-31 | Apparatus for monitoring displacement |
Family Applications Before (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838323685A Pending GB8323685D0 (en) | 1983-09-03 | 1983-09-03 | Monitoring displacement |
| GB08327814A Expired GB2146120B (en) | 1983-09-03 | 1983-10-18 | Photoacoustic force sensor |
Country Status (1)
| Country | Link |
|---|---|
| GB (3) | GB8323685D0 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3621427A1 (en) * | 1985-06-28 | 1987-01-22 | Simmonds Precision Products | MEASURING SYSTEM |
| EP0360449A2 (en) * | 1988-09-19 | 1990-03-28 | Simmonds Precision Products Inc. | Acoustic transducing arrangements and methods |
| EP1996957A2 (en) * | 2006-03-15 | 2008-12-03 | Venkata Guruprasad | Universal frequency generation and scaling |
| WO2009071746A1 (en) * | 2007-12-05 | 2009-06-11 | Valtion Teknillinen Tutkimuskeskus | Device for measuring pressure, variation in acoustic pressure, a magnetic field, acceleration, vibration, or the composition of a gas |
| US8850893B2 (en) | 2007-12-05 | 2014-10-07 | Valtion Teknillinen Tutkimuskeskus | Device for measuring pressure, variation in acoustic pressure, a magnetic field, acceleration, vibration, or the composition of a gas |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4897541A (en) * | 1984-05-18 | 1990-01-30 | Luxtron Corporation | Sensors for detecting electromagnetic parameters utilizing resonating elements |
| US4678905A (en) * | 1984-05-18 | 1987-07-07 | Luxtron Corporation | Optical sensors for detecting physical parameters utilizing vibrating piezoelectric elements |
| US4713540A (en) * | 1985-07-16 | 1987-12-15 | The Foxboro Company | Method and apparatus for sensing a measurand |
| GB8530809D0 (en) * | 1985-12-13 | 1986-01-22 | Gen Electric Co Plc | Sensor |
| GB2187551B (en) * | 1986-03-04 | 1990-03-14 | Gen Electric Plc | Radiation detector |
| GB8610253D0 (en) * | 1986-04-26 | 1986-05-29 | Stc Plc | Resonator device |
| GB2194054A (en) * | 1986-08-15 | 1988-02-24 | Gen Electric Co Plc | Magnetometer |
| GB2194049B (en) * | 1986-08-15 | 1990-04-25 | Gen Electric Plc | A sensor |
| GB2197069B (en) * | 1986-11-03 | 1990-10-24 | Stc Plc | Sensor device |
| GB8701556D0 (en) * | 1987-01-24 | 1987-02-25 | Schlumberger Electronics Uk | Sensors |
| GB2208931B (en) * | 1987-08-19 | 1991-06-26 | Stc Plc | Mechanical oscilattor |
| FR2636744B1 (en) * | 1988-09-19 | 1993-01-22 | Crouzet Sa | VIBRATING RESONATOR WITH OPTICAL EXCITATION AND DETECTION FOR SENSOR USE |
| US4972076A (en) * | 1988-09-29 | 1990-11-20 | Schlumberger Industries Limited | Solid state sensor with dual resonant vibratable members |
| FR2638519B1 (en) * | 1988-11-02 | 1990-12-28 | Asulab Sa | DEVICE FOR MEASURING A PHYSICAL QUANTITY |
| US5265479A (en) * | 1989-10-17 | 1993-11-30 | Lucas Industries Public Limited Company | Micro resonator |
| GB8923374D0 (en) * | 1989-10-17 | 1989-12-06 | Lucas Ind Plc | Sensor |
| DE4230087A1 (en) * | 1992-09-09 | 1994-03-10 | Bezzaoui Hocine Dipl Ing | Integrated optical micro-mechanical sensor for measuring physical or chemical parameters - has strip waveguide applied to etched membrane acting as integrated measuring path |
| ATE251302T1 (en) * | 1997-07-21 | 2003-10-15 | Euratom | LIGHT INTENSITY SENSOR ELEMENT AND METHOD FOR LIGHT BEAM MODULATION AND DEVICE USING SUCH A SENSOR ELEMENT |
| GB2508908B (en) | 2012-12-14 | 2017-02-15 | Gen Electric | Resonator device |
| CN112097700B (en) * | 2020-09-10 | 2021-11-02 | 中国科学院重庆绿色智能技术研究院 | Wireless strain sensing system and monitoring method based on frequency reconfigurable antenna |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB663946A (en) * | 1947-07-04 | 1951-01-02 | Georges Henri Dion | Improvements in level measuring apparatus |
| GB1420043A (en) * | 1972-07-31 | 1976-01-07 | Romen Faser Kunststoff | Method and apparatus for providing space security |
| GB1479316A (en) * | 1973-06-15 | 1977-07-13 | Rosencwaig A | Methods and means for investigating substances |
| GB2020025A (en) * | 1978-04-28 | 1979-11-07 | Us Energy | Optoacoustic spectroscopy method and apparatus |
| GB2023822A (en) * | 1978-05-26 | 1980-01-03 | Allied Chem | Photoacoustic raman spectroscopy |
| GB1600883A (en) * | 1977-02-14 | 1981-10-21 | Gen Resistance | System and method of measuring fluid pressure force |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4255971A (en) * | 1978-11-01 | 1981-03-17 | Allan Rosencwaig | Thermoacoustic microscopy |
-
1983
- 1983-09-03 GB GB838323685A patent/GB8323685D0/en active Pending
- 1983-10-18 GB GB08327814A patent/GB2146120B/en not_active Expired
-
1984
- 1984-07-31 GB GB08419491A patent/GB2146123B/en not_active Expired
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB663946A (en) * | 1947-07-04 | 1951-01-02 | Georges Henri Dion | Improvements in level measuring apparatus |
| GB1420043A (en) * | 1972-07-31 | 1976-01-07 | Romen Faser Kunststoff | Method and apparatus for providing space security |
| GB1479316A (en) * | 1973-06-15 | 1977-07-13 | Rosencwaig A | Methods and means for investigating substances |
| GB1600883A (en) * | 1977-02-14 | 1981-10-21 | Gen Resistance | System and method of measuring fluid pressure force |
| GB2020025A (en) * | 1978-04-28 | 1979-11-07 | Us Energy | Optoacoustic spectroscopy method and apparatus |
| GB2023822A (en) * | 1978-05-26 | 1980-01-03 | Allied Chem | Photoacoustic raman spectroscopy |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3621427A1 (en) * | 1985-06-28 | 1987-01-22 | Simmonds Precision Products | MEASURING SYSTEM |
| EP0360449A2 (en) * | 1988-09-19 | 1990-03-28 | Simmonds Precision Products Inc. | Acoustic transducing arrangements and methods |
| EP0360449A3 (en) * | 1988-09-19 | 1990-06-13 | Simmonds Precision Products Inc. | Acoustic transducing arrangements and methods |
| EP1996957A2 (en) * | 2006-03-15 | 2008-12-03 | Venkata Guruprasad | Universal frequency generation and scaling |
| EP1996957A4 (en) * | 2006-03-15 | 2012-12-26 | Venkata Guruprasad | Universal frequency generation and scaling |
| WO2009071746A1 (en) * | 2007-12-05 | 2009-06-11 | Valtion Teknillinen Tutkimuskeskus | Device for measuring pressure, variation in acoustic pressure, a magnetic field, acceleration, vibration, or the composition of a gas |
| CN101970339B (en) * | 2007-12-05 | 2014-04-16 | 芬兰技术研究中心 | Device for measuring pressure, variation in acoustic pressure, a magnetic field, acceleration, vibration, or the composition of a gas |
| US8850893B2 (en) | 2007-12-05 | 2014-10-07 | Valtion Teknillinen Tutkimuskeskus | Device for measuring pressure, variation in acoustic pressure, a magnetic field, acceleration, vibration, or the composition of a gas |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8327814D0 (en) | 1983-11-16 |
| GB8323685D0 (en) | 1983-10-05 |
| GB8419491D0 (en) | 1984-09-05 |
| GB2146120A (en) | 1985-04-11 |
| GB2146120B (en) | 1987-01-14 |
| GB2146123B (en) | 1987-04-23 |
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