EP0239608A1 - An apparatus for determining the condition of a material, in particular the adsorption of a gas or liquid on said material - Google Patents
An apparatus for determining the condition of a material, in particular the adsorption of a gas or liquid on said materialInfo
- Publication number
- EP0239608A1 EP0239608A1 EP19860905945 EP86905945A EP0239608A1 EP 0239608 A1 EP0239608 A1 EP 0239608A1 EP 19860905945 EP19860905945 EP 19860905945 EP 86905945 A EP86905945 A EP 86905945A EP 0239608 A1 EP0239608 A1 EP 0239608A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- assembly
- piezo
- electric
- electrode assembly
- mirrors
- 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.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
- G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/025—Change of phase or condition
- G01N2291/0256—Adsorption, desorption, surface mass change, e.g. on biosensors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0423—Surface waves, e.g. Rayleigh waves, Love waves
Definitions
- interdigital transducers For exciting such waves and recovering again electri ⁇ cal vibrations, use can be made of so-called interdigital transducers.
- the latter comprise two comb-shaped electrodes made of metal foil on the surface of a piezo-electric wafer, the teeth of said electrodes being intercaleted said teeth having a width which is equal to 1/4 of the pitch of the teeth.
- An elastic wave is produced then which is directed perpendicularly to the teeth, the wave-length thereof being equal to said pitch.
- the amplitude of said vibration and the sharpness of resonance increase with the number of teeth.
- the latter can, for instance, be included in an oscillator circuit which,because of a change - 2 - in the condition of the layer, and, hus, of the transit time of the elastic wave, will be more or less detuned.
- Information in respect , ⁇ f the character of the adsorbed substance can be derived therefrom.
- Such an apparatus can also be used for other changes in condition of the surface layer, or for mutual ⁇ ly comparing different kinds of surface layers.
- the apparatus according to the invention for de ⁇ termining the condition of a material, and in particular the adsorption of a gas or liquid on this material comprises a substrate with a plane surface possessing, at least near said surface, piezo-electric characteristics, an electrode assembly provided on said surface and consisting of thin metallic layers in the form of two combs with mutually intercalated teeth, said assembly being adapted for applying thereto an electrical alternating voltage with an adapted frequency, in order to produce an elastic wave in the piezo-electric material directed transversely to said teeth, and at least one surface layer of the material of which the condition is to be determined, which is arranged laterally of said assembly on said surface, said apparatus being characterised in that, at both sides of the comb-shaped electrode assembly.
- a mirror for the elastic waves produced by said assembly is arranged, said mirrors being, formed by substantially rectilinear surface variations extending parallel to the teeth of the electrodes, and being situated at such a distance from said electrode assembly that the waves reflected between said mirrors are in phase at said electrode assembly if the surface layer is in a given reference condition, said layer being provided at least between said - 3 - electrode assembly and one of said mirrors.
- This structure is comparable to an interferometer known from optrics, and is extremely sensitive for small transit time differences between the electrode assembly and the mirrors. At a variation of the transit time, so that the different waves are no longer in phase, the energy storage in this system will change, which is sensed as an impedance variation by the electrical circuit causing the elastic vibration, and such variation can be easily detected. It is also possible to provide a second and similar electrode assembly at such a distance from the first one that, in the reference condition, the different waves will be in phase also there, which second assembly is connected with an electric measuring circuit. When, in this respect, reference is made to distances and points in which vibrations are in phase, this holds, of course, for points of the electrode assemblies which can be considered as a centre of vibration.
- Said mirrors consist, in particular, of a plurality of parallel lines having a mutual distance of a whole number of quarter wave-lengths of the elastic wave in the reference condition of the surface layer, said number being chosen so that a substantially complete reflection is obtained.
- Said mirror lines can consist of metallic layers provided on the piezo-electric surface, or of shallow grooves formed in said piezo-electric surface.
- the piezo-electric surface can be in the form of a cover layer on a semiconductor substrate in which the associated circuits are integrated.
- Fig. 1 a diagrammatic view of the basic shape of the apparatus of the invention
- FIG. 2 a view at a larger scale of a portion of Fig. 1 ; and Fig. 3 a corresponding representation of a modified embodiment .
- the apparatus of the invention comprises a wafer 1 of a piezo-electric material, or at least a piezo-electric covering layer on a suitable substrate, said covering layer 1 - 4 - having a sufficient thickness for being adapted to form there ⁇ in so-called Rayleigh-waves with a penetration depth of several ⁇ m.
- interdigital electrode assembly 2 On this wafer 1 a so-called interdigital electrode assembly 2 is provided. A portion of such an assembly is shown in Fig. 2 at a larger scale. Beyond the portion of the wafer 1 below said assembly, said wafer 1 does not need to be piezo- electrical, so that, if the wafer 1 is not piezo-electrical itself, only at said assembly 2 a piezo-electric covering layer is to be provided.
- the assembly 2 consists of two electrodes 3 and 4 each comprising a number of teeth 5.
- the width of said teeth 5 is equal to the width of the interspaces between two teeth 5 of different electrodes 3 and 4. If a suitable alternating voltage is applied to said electrodes, in the surface portion of the wafer 1 an elastic wave is pro ⁇ quizd having a propagation direction which is directed per ⁇ pendicularly to the direction of the teeth 5.
- the excitation frequency should be such that the wave-length, in view of the propagation velocity in the piezo-electric material, will be equal to four times the tooth width or the tooth pitch, and, in this respect, reference can be made to the literature, e.g. the publication of A.
- the distance between the lines nearest to the assembly 2 and the centre point of this assembly 2 - 5 - equals a whole number ⁇ f half wave-lengths, and the distance between the parallel lines of each set equals a whole number of quarter wave-lengths.
- Said lines operate as a mirror for the elastic wave.
- a single line 7 will not produce a complete reflection, but a number of parallel lines at a distance of a whole number of quarter wave-lengths will provide an accor ⁇ dingly better reflection. In practice some tens of lines can provide a substantially complete reflection.
- the elastic waves emitted by the electrode assembly 2 return, after reflection against the mirror lines 7, in phase with the emitted waves in the centre of the assembly 2. This will, then, operate as an interferometer, in which, in the tuned condition, a maximum energy storage occurs. However, as soon as the reflected waves do not arrive in phase in the centre point of the assembly 2, this energy is sharply reduced, which, in the electric circuit supplying the electrode assembly 2, will be sensed as a cor ⁇ responding impedance change, which can be detected in a simple manner.
- the assembly 2 is shown in Fig. 2 half-way between the line assemblies 7; this is, of course, not necessary, as long as the distances in respect both line assemblies 7 are a whole multiple of the half wave-length.
- a surface layer 8 is provided which is adapted to influence the elastic behaviour of the piezo-electric material.
- the said interferometer tuning is, of course, adapted to the wave-length which occurs in the piezo-electric material provided with this layer.
- Fig. 3 shows still an other embodiment in which a second electrode assembly 2' is provided satisfying the same phase requirements as the first assembly 2.
- the assembly 2' is connected with an electric measuring circuit, and the assembly 2 only serves for excitation of the elastic vibration.
- a piezo- electric layer 1 provided on a semiconductor substrate, which semiconductor substrate can be used, then, for forming therein integrated circuits which can be used for generating the electric vibrations and for measuring the occurring deviations.
Landscapes
- Physics & Mathematics (AREA)
- Biochemistry (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Acoustics & Sound (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
L'appareil ci-décrit destiné à la détection de l'état d'un matériau, en particulier l'adsorption d'un gaz ou d'un liquide sur ledit matériau, comprend un substrat avec une surface piézoélectrique plane et un assemblage d'électrodes consistant en des couches métalliques fines sous la forme de deux peignes ayant des dents intercalées mutuellement, sur lequel une tension à courant alternatif ayant une fréquence adaptée peut être appliqué pour produire une onde élastique dans le matériau piézoélectrique et, des deux côtés de l'assemblage à électrode en forme de peigne, un miroir est monté pour les ondes élastiques produites par ledit assemblage. Au moins entre cet assemblage et les miroirs est disposée une couche superficielle du matériau à examiner, et ce de telle sorte que les ondes réfléchies entre lesdits miroirs soient en phase au niveau dudit assemblage d'électrodes si la couche superficielle se trouve dans un état de référence donné. En particulier, un second assemblage d'électrodes similaire est prévu à une distance telle par rapport au premier assemblage que, dans l'état de référence, les ondes différentes y seront également en phase, ce second assemblage étant connecté à un circuit de mesure électrique.The apparatus described below for detecting the state of a material, in particular the adsorption of a gas or a liquid on said material, comprises a substrate with a plane piezoelectric surface and an assembly of electrodes consisting of thin metallic layers in the form of two combs having mutually interposed teeth, on which an alternating current voltage having a suitable frequency can be applied to produce an elastic wave in the piezoelectric material and, on both sides of the electrode assembly in the form of a comb, a mirror is mounted for the elastic waves produced by said assembly. At least between this assembly and the mirrors is disposed a surface layer of the material to be examined, and this so that the waves reflected between said mirrors are in phase at said electrode assembly if the surface layer is in a state of reference given. In particular, a second similar electrode assembly is provided at such a distance from the first assembly that, in the reference state, the different waves will also be in phase there, this second assembly being connected to an electrical measurement circuit. .
Description
An apparatus for determining the condition of a material, in particular the adsorption of a gas or liquid on said material,
It is known that in piezo-electric material an elastic surface wave (a so-called Rayleigh-wave) can be pro¬ duced having a penetration depth of about 2..3 μm. Since the propagation velocity is about 10 m/s, and wave-lengths of the order of magnitude of 1 μm are possible in such a material, vibrations in the order of magnitude of 1 GHz from an electric circuit can be transformed into corresponding mechanical vibrations in this manner. The low propagation velocity allows, then, to construct retardation lines with small dimensions, and also electromechanical filters can be obtained in this manner.
For exciting such waves and recovering again electri¬ cal vibrations, use can be made of so-called interdigital transducers. The latter comprise two comb-shaped electrodes made of metal foil on the surface of a piezo-electric wafer, the teeth of said electrodes being intercaleted said teeth having a width which is equal to 1/4 of the pitch of the teeth. An elastic wave is produced then which is directed perpendicularly to the teeth, the wave-length thereof being equal to said pitch. The amplitude of said vibration and the sharpness of resonance increase with the number of teeth.
For a more detailed description thereof reference can be made to a publication of A. Venema in Tijdschrift NERG 4JJ, 5 (1975) 135. In US 4312228 an apparatus is described comprising a piezo-electric- wafer with two of such composite electrodes, the part between both electrode assemblies being covered with a surface layer adapted to adsorb a gas or a liquid. This layer influences the vibration behaviour of the piezo-electric material, and thus also the propagation velocity of the elastic surface wave. If the characteristics of this layer are changed, e.g. by adsorption of an other substance, this will have an influence on the transit time of a wave between both electrode assemblies. The latter can, for instance, be included in an oscillator circuit which,because of a change
- 2 - in the condition of the layer, and, hus, of the transit time of the elastic wave, will be more or less detuned. Information in respect, αf the character of the adsorbed substance can be derived therefrom. Such an apparatus can also be used for other changes in condition of the surface layer, or for mutual¬ ly comparing different kinds of surface layers.
This known apparatus has the objection that very small changes in the condition of the surface layer cannot be detected, since small transit time variations of the elastic wave will not lead to a substantial detuning of the oscillator. Although it would be possible as such to measure the transit time of the wave, this requires complicated and expensive measuring apparatuses which, in many cases, will render the apparatus unsuitable for practical purposes. It is an object of the invention to provide such an apparatus having a substantially higher sensitivity than the known apparatus.
The apparatus according to the invention for de¬ termining the condition of a material, and in particular the adsorption of a gas or liquid on this material, comprises a substrate with a plane surface possessing, at least near said surface, piezo-electric characteristics, an electrode assembly provided on said surface and consisting of thin metallic layers in the form of two combs with mutually intercalated teeth, said assembly being adapted for applying thereto an electrical alternating voltage with an adapted frequency, in order to produce an elastic wave in the piezo-electric material directed transversely to said teeth, and at least one surface layer of the material of which the condition is to be determined, which is arranged laterally of said assembly on said surface, said apparatus being characterised in that, at both sides of the comb-shaped electrode assembly. a mirror for the elastic waves produced by said assembly is arranged, said mirrors being, formed by substantially rectilinear surface variations extending parallel to the teeth of the electrodes, and being situated at such a distance from said electrode assembly that the waves reflected between said mirrors are in phase at said electrode assembly if the surface layer is in a given reference condition, said layer being provided at least between said
- 3 - electrode assembly and one of said mirrors.
This structure is comparable to an interferometer known from optrics, and is extremely sensitive for small transit time differences between the electrode assembly and the mirrors. At a variation of the transit time, so that the different waves are no longer in phase, the energy storage in this system will change, which is sensed as an impedance variation by the electrical circuit causing the elastic vibration, and such variation can be easily detected. It is also possible to provide a second and similar electrode assembly at such a distance from the first one that, in the reference condition, the different waves will be in phase also there, which second assembly is connected with an electric measuring circuit. When, in this respect, reference is made to distances and points in which vibrations are in phase, this holds, of course, for points of the electrode assemblies which can be considered as a centre of vibration.
Said mirrors consist, in particular, of a plurality of parallel lines having a mutual distance of a whole number of quarter wave-lengths of the elastic wave in the reference condition of the surface layer, said number being chosen so that a substantially complete reflection is obtained.
Said mirror lines can consist of metallic layers provided on the piezo-electric surface, or of shallow grooves formed in said piezo-electric surface.
In particular the piezo-electric surface can be in the form of a cover layer on a semiconductor substrate in which the associated circuits are integrated.
The invention will be elucidated below in more detail by reference to a drawing, showing in:
Fig. 1 a diagrammatic view of the basic shape of the apparatus of the invention;
Fig. 2 a view at a larger scale of a portion of Fig. 1 ; and Fig. 3 a corresponding representation of a modified embodiment .
'The apparatus of the invention comprises a wafer 1 of a piezo-electric material, or at least a piezo-electric covering layer on a suitable substrate, said covering layer 1
- 4 - having a sufficient thickness for being adapted to form there¬ in so-called Rayleigh-waves with a penetration depth of several μm.
On this wafer 1 a so-called interdigital electrode assembly 2 is provided. A portion of such an assembly is shown in Fig. 2 at a larger scale. Beyond the portion of the wafer 1 below said assembly, said wafer 1 does not need to be piezo- electrical, so that, if the wafer 1 is not piezo-electrical itself, only at said assembly 2 a piezo-electric covering layer is to be provided.
As shown in Fig. 2 the assembly 2 consists of two electrodes 3 and 4 each comprising a number of teeth 5. The width of said teeth 5 is equal to the width of the interspaces between two teeth 5 of different electrodes 3 and 4. If a suitable alternating voltage is applied to said electrodes, in the surface portion of the wafer 1 an elastic wave is pro¬ duced having a propagation direction which is directed per¬ pendicularly to the direction of the teeth 5. The excitation frequency should be such that the wave-length, in view of the propagation velocity in the piezo-electric material, will be equal to four times the tooth width or the tooth pitch, and, in this respect, reference can be made to the literature, e.g. the publication of A. Venema in Tijdschrift NERG 40_, 5 (1975) 135. The wave-lengths obtainable with such an assembly will, therefore, depend on the precision of manufacturing such an assembly. The etching techniques developed for integrated semiconductor circuits allow the production of very fine electrode assemblies, so that wave-lengths in the order of magnitude of 1 μm, i.e. frequencies of several GHz (at a pro¬ pagation velocity of 3.10 m/s in the piezo-electric material) are possible. This means that a relatively very small path length on the wafer 1 already comprises a very large number of wave-lengths of the elastic wave. At both sides of the assembly 2 a plurality of lines
7 is provided on the surface of the wafer 1, which consist either of vapour-deposited metal layers or of fine grooves formed into the surface. The distance between the lines nearest to the assembly 2 and the centre point of this assembly 2
- 5 - equals a whole number αf half wave-lengths, and the distance between the parallel lines of each set equals a whole number of quarter wave-lengths. Said lines operate as a mirror for the elastic wave. A single line 7 will not produce a complete reflection, but a number of parallel lines at a distance of a whole number of quarter wave-lengths will provide an accor¬ dingly better reflection. In practice some tens of lines can provide a substantially complete reflection. The elastic waves emitted by the electrode assembly 2 return, after reflection against the mirror lines 7, in phase with the emitted waves in the centre of the assembly 2. This will, then, operate as an interferometer, in which, in the tuned condition, a maximum energy storage occurs. However, as soon as the reflected waves do not arrive in phase in the centre point of the assembly 2, this energy is sharply reduced, which, in the electric circuit supplying the electrode assembly 2, will be sensed as a cor¬ responding impedance change, which can be detected in a simple manner. The assembly 2 is shown in Fig. 2 half-way between the line assemblies 7; this is, of course, not necessary, as long as the distances in respect both line assemblies 7 are a whole multiple of the half wave-length.
On the surface of the wafer 1, at least between the lines 7 and the electrode assembly 2, a surface layer 8 is provided which is adapted to influence the elastic behaviour of the piezo-electric material. The said interferometer tuning is, of course, adapted to the wave-length which occurs in the piezo-electric material provided with this layer.
When the condition of the layer 8 changes, also the vibration behaviour of the piezo-electric material is changed, leading to a disturbance of the said vibration condition. Such a change will, for instance, occur if the layer can adsorb an other substance so that its mass will increase. Use can be made thereof for detecting gases or liquids which can be adsorbed on the layer 8, and already very small quantities thereof will be sufficient for producing a substantial dis¬ turbance of the vibration equilibrium.
Although it is possible to provide only one surface layer 8 at one side of the electrode assembly 2, the symmetric¬ al embodiment of Fig. 1 is preferred since, then, the sensi-
- 6 - tivity will be higher.
Fig. 3 shows still an other embodiment in which a second electrode assembly 2' is provided satisfying the same phase requirements as the first assembly 2. The assembly 2' is connected with an electric measuring circuit, and the assembly 2 only serves for excitation of the elastic vibration.
In this manner it becomes possible to obtain an extremely sensitive gas and/or liquid detector by means of which very small concentrations can be detected. Of course also other phenomena can be detected which influence the behaviour αf the surface layer 8.
Sometimes it will be advisable to use a piezo- electric layer 1 provided on a semiconductor substrate, which semiconductor substrate can be used, then, for forming therein integrated circuits which can be used for generating the electric vibrations and for measuring the occurring deviations.
Claims
1. An apparatus for detecting the condition of a material, in particular the adsorption of a gas or liquid to said material, comprising a substrate with a plane surface having, at least near said surface, piezo-electric characte- ristics, an electrode assembly provided on said surface and consisting of thin metallic layers in the form of two combs with mutually intercalated teeth, said assembly being adapted for applying thereto an electrical alternating voltage with an adapted frequency, in order to produce an elastic wave in the piezo-electric material directed transversely to said teeth, and at least one surface layer of the material of which the condition is to be determined, which is arranged laterally of said assembly on said surface, said apσaratus beinα c h a r a c t e r i s e d in that, at both sides of the comb- shaped electroce assembly, a mirror for the elastic waves produced by said assembly is arranged, said mirrors being formed by substan ially rectilinear surface variations ex¬ tending parallel to the teeth of the electrodes, and being situated at such a distance from said electrode assembly that the waves reflected between said mirrors are in phase at said electrode assembly if the surface layer is in a given reference condition, said layer being provided at least between said electrode assembly and one of said mirrors.
2. Apparatus according claim 1, c h a r a c t e r i - s e d in that a second and similar electrode assembly is pro¬ vided at such a distance from the first one so that, in the reference condition, the different waves will be in phase also there, which second assembly is connected to an electric measuring circuit.
3. Apparatus according claim l or 2, c h a r a c t e ¬ r i s e d in that said mirrors consist, in particular, of a plurality of parallel lines having a mutual distance of a whole number of quarter wave-lengths of the elastic wave in the reference condition of the surface layer, said number being chosen so that a substantially complete reflection is obtained.
4. Apparatus according to any one of claims 1..3, - 8 - c h a r a c t e r i s e d in that said mirror lines consist of metallic layers provided on the piezo-electric surface.
5. Apparatus according to any one of claims 1..3, c h a r a c t e r i s e d in that said mirror lines consist of shallow grooves formed in said piezo-electric surface.
6. Apparatus according to any one of claims 1..5, c h a r a c t e r i s e d in that the piezo-electric surface is formed as a cover layer on a semiconductor substrate in which the associated circuits are integrated.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8502634A NL8502634A (en) | 1985-09-26 | 1985-09-26 | APPARATUS FOR DETERMINING THE CONDITION OF A MATERIAL, IN PARTICULAR THE ADSORPTION OF A GAS OR LIQUID ON THIS MATERIAL. |
| NL8502634 | 1985-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0239608A1 true EP0239608A1 (en) | 1987-10-07 |
Family
ID=19846619
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19860905945 Withdrawn EP0239608A1 (en) | 1985-09-26 | 1986-09-26 | An apparatus for determining the condition of a material, in particular the adsorption of a gas or liquid on said material |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0239608A1 (en) |
| JP (1) | JPH01500052A (en) |
| NL (1) | NL8502634A (en) |
| WO (1) | WO1987002134A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4905701A (en) * | 1988-06-15 | 1990-03-06 | National Research Development Corporation | Apparatus and method for detecting small changes in attached mass of piezoelectric devices used as sensors |
| GB8922601D0 (en) * | 1989-10-06 | 1989-11-22 | Rolls Royce Plc | Thermal piezoelectric microbalance and method of using the same |
| GB2244557A (en) * | 1990-06-01 | 1991-12-04 | Marconi Gec Ltd | Acoustic wave biosensor |
| DE19850803A1 (en) * | 1998-11-04 | 2000-05-11 | Bosch Gmbh Robert | Sensor arrangement and a method for determining the density and viscosity of a liquid |
| DE19850801A1 (en) * | 1998-11-04 | 2000-05-11 | Bosch Gmbh Robert | Method and device for operating a microacoustic sensor arrangement |
| US20070041870A1 (en) * | 2003-03-26 | 2007-02-22 | Kazushi Yamanaka | Sensor head, gas sensor and sensor unit |
| JP2005331326A (en) * | 2004-05-19 | 2005-12-02 | Japan Radio Co Ltd | Elastic wave sensor |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4121467A (en) * | 1977-05-31 | 1978-10-24 | The United States Of America As Represented By The Secretary Of The Army | Non-destructive technique for surface wave velocity measurement |
| US4312228A (en) * | 1979-07-30 | 1982-01-26 | Henry Wohltjen | Methods of detection with surface acoustic wave and apparati therefor |
-
1985
- 1985-09-26 NL NL8502634A patent/NL8502634A/en not_active Application Discontinuation
-
1986
- 1986-09-26 JP JP50512386A patent/JPH01500052A/en active Pending
- 1986-09-26 EP EP19860905945 patent/EP0239608A1/en not_active Withdrawn
- 1986-09-26 WO PCT/NL1986/000030 patent/WO1987002134A1/en not_active Application Discontinuation
Non-Patent Citations (1)
| Title |
|---|
| See references of WO8702134A1 * |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1987002134A1 (en) | 1987-04-09 |
| NL8502634A (en) | 1987-04-16 |
| JPH01500052A (en) | 1989-01-12 |
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| 17P | Request for examination filed |
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| 18D | Application deemed to be withdrawn |
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Inventor name: VENEMA, ADRIANUS |