GB2215049A - Sound cell for analysing fluids and having isolating mounts for the transducer - Google Patents
Sound cell for analysing fluids and having isolating mounts for the transducer Download PDFInfo
- Publication number
- GB2215049A GB2215049A GB8802251A GB8802251A GB2215049A GB 2215049 A GB2215049 A GB 2215049A GB 8802251 A GB8802251 A GB 8802251A GB 8802251 A GB8802251 A GB 8802251A GB 2215049 A GB2215049 A GB 2215049A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cell
- transducer
- housing
- sound
- sound cell
- 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
- 239000012530 fluid Substances 0.000 title claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 229910052751 metal Inorganic materials 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims abstract description 9
- 238000005259 measurement Methods 0.000 claims abstract description 8
- 230000005540 biological transmission Effects 0.000 claims description 8
- 239000011521 glass Substances 0.000 claims description 4
- 229910001220 stainless steel Inorganic materials 0.000 claims description 4
- 239000010935 stainless steel Substances 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 2
- 229920002313 fluoropolymer Polymers 0.000 claims 2
- 230000002093 peripheral effect Effects 0.000 claims 2
- 229920003023 plastic Polymers 0.000 abstract description 5
- 239000004033 plastic Substances 0.000 abstract description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 abstract description 4
- 238000000034 method Methods 0.000 abstract description 3
- 229910052697 platinum Inorganic materials 0.000 abstract description 2
- 239000000126 substance Substances 0.000 abstract description 2
- 238000002955 isolation Methods 0.000 abstract 1
- 230000006641 stabilisation Effects 0.000 abstract 1
- 238000011105 stabilization Methods 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 28
- 210000004027 cell Anatomy 0.000 description 26
- 210000005056 cell body Anatomy 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000004065 semiconductor Substances 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 230000003071 parasitic effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000005234 chemical deposition Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 1
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003534 oscillatory effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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
- G01N29/024—Analysing fluids by measuring propagation velocity or propagation time of acoustic waves
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
A sound cell for the composition analysis of binary fluid mixtures from sonic velocity measurement comprises a multi-port housing (12, 13, 20) in which two transducers (16) are mounted. The transducers (16) are supported on pins (31) which provide both acoustic isolation and electrical contact and by further pins 33 each carrying a leaf spring to engage the other side of the transducers. This arrangement allows the use of metal gaskets 15 which transmit unwanted acoustic signals from outside the cell but which are necessary for certain chemical mixtures where plastics gaskets cannot be used. The gas to be analysed is passed through a coiled tube 19 for temperature stabilization and the temperature is measured with a platinum resistance thermometer 18. A pulse technique is used to measure the sound velocity at the known temperature and a computer controlled system is disclosed for determining the mixture composition. <IMAGE>
Description
ACOUSTIC DEVICES
This invention relates to devices for the measurement of sound velocity in a gas or vapour, and in particular to devices operating at ultrasonic frequencies.
Gas phase processes, such as the chemical deposition of semiconductor layers from gaseous reactants (CVD), often require accurate control of the gas composition. In the past this control has been effected by controlling the flow rates of the constituent gases into the reaction zone. This control is somewhat uncertain and is inadequate for the formation of certain compound semiconductor structures in which very precise control of the semiconductor composition is essential. In an attempt to overcome this problem it has been suggested that gas composition may be determined by measurement of sound velocity.As is well known, the velocity V of sound in a binary gas mixture is given by the expression:
where T is the weighted average of the ratios of the principal specific heats for the two gases in the mixture, R is the gas constant, T is the absolute temperature, and N is the mean molar mass of the gas mixture. The molar fraction, X, of a gas in the binary mixture is then determined from the molecular masses
M1 and M2 of the two gases from the equation
Typical sound velocity meters employ a pair of ultrasonic transducer mounted in a cell through which the gas mixture is directed.The transit time of sonic pulses between the transducers is determined to obtain a measure of the acoustic velocity.The body of the sound cell is of multipart copnstruction to allow fitting and replacement of the transducers, the various body parts being sealed together via resilient plastics gaskets.
These gaskets attenuate sonic vibrations transmitted via the cell body and thus inhibit the propagation of unwanted parasitic signals.
Such an arrangement cannot be employed in the metal organic deposition processes (MOCVD) that are employed for the preparation of compound semiconductor structures. It has been found that plastics materials are very slightly permeable to oxygen and water vapour.
Although the quantities of gas that diffuse or permeate through said materials are very small, nevertheless this diffusion is sufficient to have a significant adverse effect on semiconductor processing. Attempts to overcome this problem by the use of metal e.g. stainless steel or gold, gaskets introduces the problem of acoustic coupling through the body of the cell with a consequent loss of sensitivity and accuracy.
The object of the present invention is to minimise or to overcome this disadvantage.
According to the invention there is provided a sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within said housing and arranged to transmit and receive sonic signals via a fluid path therebetween, and mounting means for each said transducer, wherein each said mounting means includes an array of support pins extending from the housing and against which the transducer abuts.
According to the invention there is further provided a sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within the housing and arranged to transmit and receive sonic signals via a fluid path therebetween, support means one for each said transducer and each comprising an array of three support pins, extending from the housing and against which the transducer abuts, and spring means whereby each said transducer is urged against its respective support pins, and wherein said support pins and spring means provide electrical contact to the transducer.
Typically the fluid is a gas, although the cell may also be employed from the analysis of liquids.
An embodiment of the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a part sectional view of the sound
cell;
Figure 2 is a plan view of the transducer mount
of the cell of Figure 1;
Figure 3 shows the detail of the transducer
mount;
Figure 3a shows a retaining spring employed on
the transducer mount of Figure 3 Figure 4 is a schematic diagram of a
composition measurement arrangement employing
the cell of Figures 1 and 2.
and Figure 5 illustrates the sonic waveform and the
manner in which this waveform is analysed to
provide sonic velocity information.
Referring to Figures 1 to 3, the sound cell inlcudes a multipart, generally cylindrical, hollow body 11 comprising a centre portion 12 and two end plates 13.
Each end plate 13 supports an extension piece 20 of reduced diameter. The structure is formed from an inert metal such as stainless steel. The end plates are secured to the body by set screws 14, a metal gasket 15 being employed to effect a gas tight seal. Typically the gasket material is gold. Each end plate 13 supports a piezoelectric tranducer 16, the transducer being mutually aligned so as to transmit and receive sonic signals via the body cavity therebetween.
As shown in Figures 2 and 3, each piezoelectric transducer 16 is supported on three or more pins 31 secured to the respective end portion by glass to metal seals 32. The end faces of the pins 31 provide the necessary axial alignment of the transducer. This method of mounting the transducer provides a significant reduction in acoustic coupling between the transducer and the cell body as compared with a conventional arrangement. Radial alignment of the transducer 16 is determined by three further pins 33 each of which has circumferential groove 34 near its free end for receiving a leaf spring 35 (Figure 3c) whereby the transducer 16 is urged against the pins 31. The further pins 33 are also supported in the glass to metal seals 32.Advantageously the transducer 16 is provided with an inert plastics e.g. fluorocarbon, collar 36 which collar is a sliding fit between the pins 33 thus ensuring radial alignment of the transducer 16. The collar 34 also attenuates the propagation of radial modes 6f oscillation of the transducer into the cell body.
As can be seen from Figure 3a, each leaf spring 35 has a bifurcated portion 351 for engaging the groove in the respective pin 33, and a generally wedge-shaped portion 352 the apex of which abuts the transducer so to urge the transducer against the pnis 31.
The pins 31 provide electrical contact to the rear face of the transducer 16, and the springs 35 provide electrical contact to the front face. Each set of these pins 31 and further pins 33 are connected in parallel, the set of pins being coupled to a coaxial connector 17 mounted on the extension member 20 whereby electrical signals may be transmitted to or from the transducer.
The frequency of operation of the transducer is determined by the thickness and the chemical composition of the piezoelectric material. We prefer to employ the material PZT-5A. This material is a modified lead zirconate titanate ceramic. At a 2mm thickness, a disc of the material has an axial mode resonant frequency of about 1MHz.
To minimise the effect of parasitic oscillation of the transducers in modes other than the transverse mode, it is preferred to drive the transmitter transducer in a discontinuous manner. Typically the transducer is driven by a series of rectangular pulses, each pulse causing the transducer to 'ring' at the desired 1MHz frequency.
As the velocity of sound in a gas is a function of absolute temperature, it is necessary to provide a means of measuring the gas temperature within the cell.
For this purpose a platinum resistance thermometer 18 (Figure 1) is mounted in thermal contact with the cell body. Gas entering the cell is first passed through a coiled tube 19 also in thermal contact with the cell body before passing through inlet 20 into the cell cavity. This ensures that the gas is at the same temperature as the cell body. Advantageously the cell is mounted in an isothermal enclosure (not shown).
The cell may be employed for the determination of sound velocity by measuring the the transit time of sonic pulses through the gas within the cell cavity.
This transit time, together with a measure of the gas temperature and the distance between the transducers may then be used to calculate the gas composition as previously described.
The arrangement is operated in a pulsed mode.
This overcomes the problem of parasitic oscillation 6f the cell body with the consequent reduction of signal to noise ratio. It is preferred that the transit time of each sonic pulse through the gas in the cell is less than two or three resonant periods of the cell body.
Driving the transmitter transducer at a relatively low repetition rate and using short drive pulse lengths equal to one half of the axial resonant frequency of the transducer further improves the transmission and reception characteristics of the sonic pulses. Under these conditions, there is very little exitation of unwanted radial modes of oscillation of the transmitter transducer. The use of the plastics collars 36 enhances suppression of these unwanted modes.
Typically the transmitter transducer is driven by rectangular voltage pulses of 100 vots amplitude.
Using a 2mm thick transducer of 20mm diameter we have found that a pulse length of 0.5 microseconds and a repetition frequency of 100 Hz provides adequate suppression of unwanted parasitic modes and an effective signal to noise ratio.
Figure 4 shows in schematic form a gas composition measurement arrangement employing the cell of Figures 1 to 3. The transmitter transducer of the cell 41 is driven by rectangular pulses from a pulse generator 42 the output of which is also coupled to a connector/timer circuit 43. The receiver transducer of the cell 41 is coupled via a transmission line 44 to a tuned or band-pass amplifier 45 responsive to the frequency of the transverse oscillatory mode of the transducers. The output of the amplifier comprises a wave packet delayed, with reference to the corresponding drive pulse, by a period T1 (Fig.5) corresponding to the transit time through the gas mixture between the two transducers. There is also a very small constant delay arising from the propagation time through the transducers and amplifier.The amplifier output is fed to a single channel analyser 46 which circuit functions both as a discriminator 46a and a precision trigger circuit 46b. The single channel analyser responds to a particular signal peak, i.e. the first peak whose amplitude suceeds a predetermined threshold, in the wave packet. Appropriate adjustment of upper and lower threshold levels V1. V2 (Fig. 5) of the discriminator 46c allows this particular signal peak to be selected.
In response to reception of this signal peak the precision trigger 46b outputs a pulse to the counter timer circuit 43 where a time comparison is made between the transmitted and received signals. It will be appreciated that, by selection of a particular peak of the received signal, the output of the precision trigger circuit 46b consists of pulses which are precisely selected to the time of the selected signal peak and which are independent of small changes in rigid amplitude caused e.g. by drift in the gain of the tuned amplifier 45.
The cell temperature is monitored by a temperature probe 47, e.g. a platium resistance thermometer and a corresponding output signal is generated by a temperature measurement circuit 48. A digital signal corresponding to the cell temperature is fed, together with the output of the counter/timer to a computer 49 which performs the calculations resulting in a measure of the gas composition.
The small inherent propagation delays referred to above may be determined by calibration of the cell with pure gases, e.g. hydrogen and nitrogen, whose characteristics are well known. This calibration can also be used to give an accurate measures of the distance between the transducer.
It will be understood that the description of the gas composition measurement arrangement given above is by way of example only and that the sonic cell is not limited to this particular application.
Claims (11)
1. A sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within said housing and arranged to transmit and receive sonic signals via a fluid path therebetween, and mounting means for each said transducer, wherein each said mounting means includes an array of support pins extending from the housing and against which the transducer abuts.
2. A sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within the housing and arranged to transmit and receive sonic signals via a fluid path therebetween, support means one for each said transducer and each comprising an array of three support pins, extending from the housing and against which the transducer abuts, and spring means whereby each said transducer is urged against its respective support pins, and wherein said support pins and spring means provide electrical contact to the transducer. Typically the fluid is a gas, although the cell may also be employed from the analsis of liquids.
3. A sound cell as claimed in Claim 1 or 2, wherein each said transducer is in the form of a disc.
4. A sound cell as claimed in Claim 3, wherein each said transducer is provided with a peripheral collar of a fluorocarbon polymer.
5. A sound cell as claimed in claim 4, wherein further pnis are provided adjacent said support pins and against which said collars abut whereby to provide radial alignment of the transducers.
6. A sound cell as claimed in claims 2 and 5, wherein said further pins support said spring means.
7. A sound cell as claimed in any one of claims 1 to 6, 2 or 3, and including means for providing thermal contact between the cell and a gas directed therethrough whereby the gas achieves the same temperature as the cell.
8. A sound cell as claimed in any one of Claims 1, to 7, wherein said housing is constructed of stainless steel.
9. A sound cell as claimed in Claim 8, wherein said pins are disposed in a glass to metal seals provided in the housing.
10. A sound cell substantially as described herein with reference to and as shown in Figs. 1, 2, 3 and 3c of the accompanying drawings.
11. A gas composition measurement arrangment provided with a sound cell as claimed in any one of the preceding claims.
11. A gas composition measurement arrangment provided with a sound cell as claimed in any one of the preceding claims.
Amendments to the claims have been filed as follows 1. A sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within said housing and arranged to transmit and receive sonic signals via a fluid path therebetween, and mounting means for each said transducer, wherein each said mounting means includes an array of support pins extending from the housing and against which the transducer abuts.
2. A sound cell for the analysis of fluids by the transmission of acoustic signals therethrough, the cell including a housing, a pair of transducers disposed within the housing and arranged to transmit and receive sonic signals via a fluid path therebetween, support means one for each said transducer and each comprising an array of three support pins, extending from the housing and against which the transducer abuts, and spring means whereby each said transducer is urged against its respective support pins, and wherein said support pins and spring means provide electrical contact to the transducer.
3. A sound cell as claimed in Claim 1 or 2, wherein each said transducer is in the form of a disc.
4. A sound cell as claimed in Claim 3, wherein each said transducer is provided with a peripheral collar of a fluorocarbon polymer.
5. A sound cell as claimed in claim 4, wherein further pins are provided adjacent said support pins and against which said collars abut whereby to provide radial alignment of the transducers.
6. A sound cell as claimed in claims 2 and 5, wherein said further pins support said spring means.
7. A sound cell as claimed in any one of claims 1 to 6 and including means for providing thermal contact between the cell and a gas directed therethrough whereby the gas achieves the same temperature as the cell.
8. A sound cell as claimed in any one of Claims 1 to 7, wherein said housing is constructed of stainless steel.
9. A sound cell as claimed in Claim 8, wherein said pins are disposed in a glass to metal seals provided in the housing.
10. A sound cell substantially as described herein with reference to and as shown in Figs. 1, 2, 3 and 3c of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8802251A GB2215049B (en) | 1988-02-02 | 1988-02-02 | Acoustic devices |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8802251A GB2215049B (en) | 1988-02-02 | 1988-02-02 | Acoustic devices |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8802251D0 GB8802251D0 (en) | 1988-03-02 |
| GB2215049A true GB2215049A (en) | 1989-09-13 |
| GB2215049B GB2215049B (en) | 1991-08-21 |
Family
ID=10630898
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8802251A Expired - Lifetime GB2215049B (en) | 1988-02-02 | 1988-02-02 | Acoustic devices |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2215049B (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4013665A1 (en) * | 1990-04-27 | 1991-10-31 | Fraunhofer Ges Forschung | SENSOR FOR DETECTING A SUBSTANCE IN A LIQUID |
| US5392635A (en) * | 1993-12-30 | 1995-02-28 | At&T Corp. | Acoustic analysis of gas mixtures |
| US5625140A (en) * | 1995-12-12 | 1997-04-29 | Lucent Technologies Inc. | Acoustic analysis of gas mixtures |
| US5900552A (en) * | 1997-03-28 | 1999-05-04 | Ohmeda Inc. | Inwardly directed wave mode ultrasonic transducer, gas analyzer, and method of use and manufacture |
| US6116080A (en) * | 1998-04-17 | 2000-09-12 | Lorex Industries, Inc. | Apparatus and methods for performing acoustical measurements |
| GB2397887A (en) * | 2003-01-30 | 2004-08-04 | Flotec Uk Ltd | Ultrasonic gas composition analysis device |
| EP1624300A1 (en) * | 2004-08-04 | 2006-02-08 | Flotec UK Limited | Ultrasonic fluid analysis cell with travel time measurement |
| EP1860433A1 (en) * | 2006-05-24 | 2007-11-28 | TF Instruments, Inc. | Ultrasonic resonator cell with uniform pressure on the ultrasonic transducers |
| WO2022133610A1 (en) * | 2020-12-23 | 2022-06-30 | Romet Limited | Measuring concentrations of mixed gases at an endpoint |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1225032A (en) * | 1967-03-31 | 1971-03-17 | Microtek Instr Corp | Ultrasonic acoustical analysis |
| GB2080532A (en) * | 1980-07-21 | 1982-02-03 | Balzers Hochvakuum | An oscillating crystal measuring head |
| EP0053947A1 (en) * | 1980-12-10 | 1982-06-16 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic transducer |
| GB2096860A (en) * | 1981-03-30 | 1982-10-20 | Philips Electronic Associated | Piezoelectric sound transducer |
| GB2188148A (en) * | 1986-03-19 | 1987-09-23 | Subspek Limited | Structural inspection device |
-
1988
- 1988-02-02 GB GB8802251A patent/GB2215049B/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1225032A (en) * | 1967-03-31 | 1971-03-17 | Microtek Instr Corp | Ultrasonic acoustical analysis |
| GB2080532A (en) * | 1980-07-21 | 1982-02-03 | Balzers Hochvakuum | An oscillating crystal measuring head |
| EP0053947A1 (en) * | 1980-12-10 | 1982-06-16 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic transducer |
| GB2096860A (en) * | 1981-03-30 | 1982-10-20 | Philips Electronic Associated | Piezoelectric sound transducer |
| GB2188148A (en) * | 1986-03-19 | 1987-09-23 | Subspek Limited | Structural inspection device |
Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4013665A1 (en) * | 1990-04-27 | 1991-10-31 | Fraunhofer Ges Forschung | SENSOR FOR DETECTING A SUBSTANCE IN A LIQUID |
| US5392635A (en) * | 1993-12-30 | 1995-02-28 | At&T Corp. | Acoustic analysis of gas mixtures |
| US5501098A (en) * | 1993-12-30 | 1996-03-26 | At&T Corp. | Acoustic analysis of gas mixtures |
| EP0661536B1 (en) * | 1993-12-30 | 2002-01-23 | AT&T Corp. | Acoustic analysis of gas mixtures |
| US5625140A (en) * | 1995-12-12 | 1997-04-29 | Lucent Technologies Inc. | Acoustic analysis of gas mixtures |
| EP0779511A1 (en) | 1995-12-12 | 1997-06-18 | AT&T Corp. | Acoustic analysis of gas mixtures |
| US5900552A (en) * | 1997-03-28 | 1999-05-04 | Ohmeda Inc. | Inwardly directed wave mode ultrasonic transducer, gas analyzer, and method of use and manufacture |
| US6199423B1 (en) | 1998-04-17 | 2001-03-13 | Lorex Industries, Inc. | Apparatus and methods for performing acoustical measurements |
| US6192739B1 (en) | 1998-04-17 | 2001-02-27 | Lorex Industries, Inc. | Apparatus and methods for performing acoustical measurements |
| US6279379B1 (en) | 1998-04-17 | 2001-08-28 | Lorex Industries, Inc. | Apparatus and methods for performing acoustical measurements |
| US6116080A (en) * | 1998-04-17 | 2000-09-12 | Lorex Industries, Inc. | Apparatus and methods for performing acoustical measurements |
| GB2397887A (en) * | 2003-01-30 | 2004-08-04 | Flotec Uk Ltd | Ultrasonic gas composition analysis device |
| EP1624300A1 (en) * | 2004-08-04 | 2006-02-08 | Flotec UK Limited | Ultrasonic fluid analysis cell with travel time measurement |
| EP1860433A1 (en) * | 2006-05-24 | 2007-11-28 | TF Instruments, Inc. | Ultrasonic resonator cell with uniform pressure on the ultrasonic transducers |
| WO2022133610A1 (en) * | 2020-12-23 | 2022-06-30 | Romet Limited | Measuring concentrations of mixed gases at an endpoint |
| US11879866B2 (en) | 2020-12-23 | 2024-01-23 | Romet Limited | Measuring concentrations of mixed gases at an endpoint |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8802251D0 (en) | 1988-03-02 |
| GB2215049B (en) | 1991-08-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 20080201 |