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WO1999005479A1 - Mesure de la vitesse - Google Patents

Mesure de la vitesse Download PDF

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Publication number
WO1999005479A1
WO1999005479A1 PCT/GB1998/002248 GB9802248W WO9905479A1 WO 1999005479 A1 WO1999005479 A1 WO 1999005479A1 GB 9802248 W GB9802248 W GB 9802248W WO 9905479 A1 WO9905479 A1 WO 9905479A1
Authority
WO
WIPO (PCT)
Prior art keywords
correlation
samples
detector
signal
detectors
Prior art date
Application number
PCT/GB1998/002248
Other languages
English (en)
Inventor
Michael Rigby
Original Assignee
Pcme Ltd.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Pcme Ltd. filed Critical Pcme Ltd.
Priority to AU85492/98A priority Critical patent/AU8549298A/en
Publication of WO1999005479A1 publication Critical patent/WO1999005479A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G01F1/712—Measuring the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/18—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance
    • G01P5/22—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means

Definitions

  • This invention relates to a method and apparatus for measuring the velocity of a phase of a fluid flow and in particular, but not exclusively, particles in a fluid flow.
  • the invention particularly relates to an arrangement in which particles in a fluid flow are detected by detectors and cross-correlation of signals from the detectors is used to determine the particulate velocity.
  • the invention is, however, also applicable to the measurement of the velocity of a single phase fluid flow (single phase, in the sense that all components of the flowing fluid travel together as in the case of, say, an air flow where nitrogen and oxygen travel together but not as in the case of a typical particulate flow in which the particulate would represent a first phase and would travel more slowly than the fluid carrying the particles, which fluid would represent a second phase) .
  • cross-correlation has been applied before to the problem of measuring the velocity of a fluid flow.
  • the technique has been implemented in apparatus utilising various sensing methods, such as electrodynamic or triboelectric sensing.
  • Commercial instruments are available from ABB Kent and Endress & Hauser.
  • a problem with existing cross-correlation devices is that they are either slow, if they are based on a microprocessor, or expensive, if they are based on signal -processing hardware.
  • GB 2039110 describes a device which is hardware based and which attempts to correlate data in two stages to enable a velocity measurement to be made whilst providing a continuous output of the velocity.
  • ABB Kent manufacture a device which is hardware- based and is capable of correlating up to 1024 points, in one scan, at a higher speed of operation.
  • hardware devices are much more expensive than devices based on microprocessors.
  • 4096 * 4096 16777216 multiply-add calculations (macs) .
  • a full correlation of 4096 samples is therefore not a practical possibility; for example, an Hitachi Super-H processor would perform the mac calculation in approximately 150 ns, and so the entire correlation of the full set of samples would take approximately 2.5 seconds; that is too slow for the effective monitoring of particle velocity in most applications.
  • analogue correlation because each sample can take any value between -128 and +127, the magnitude of the correlation value depends not only on the degree of matching of the samples but also on their amplitude. That can result in a maximum correlation result at a point other than where the signals are best matched.
  • the correlation result is therefore normalised. To normalise the correlation result, it is divided by:
  • the present invention provides a method of measuring the velocity of a phase of a fluid flow, the method including the following steps: providing a first signal transmitter or detector at a first location in the flow, providing a second signal transmitter or detector at a second location in the flow downstream of the first location, at least one of the first and second signal transmitters or detectors being a signal detector, ascertaining the time shift required of the signal associated with the second transmitter or detector relative to the signal associated with the first transmitter or detector to obtain close correlation of the signals, and determining the velocity of the phase of the flow from the time shift, wherein, to ascertain the time shift required for the close correlation, samples of the signal associated with the first transmitter or detector and samples of the signal associated with the second transmitter or detector are obtained and stored, at least some of the samples are retrieved from storage and subjected to a first correlation over a relatively wide
  • close correlation refers to a condition in which the correlation curve resulting from plotting the correlation result against the time shift of the signals from the detectors is substantially at its maximum value.
  • the substantially maximum value of the correlation curve may be defined in various ways. In the simplest case the maximum value of the correlation curve is defined as the highest peak in the curve but that approach is not well suited to the case where the correlation curve has twin peaks of similar height and the position corresponding to the true velocity lies between the two peaks. Accordingly it is preferred to adopt an additional “averaging” step in relation to the correlation curve. Such an "averaging" step should transform a correlation curve with twin peaks into one with a single peak. Because the results representing the correlation curve can be stored, such an averaging step can readily be carried out and need not unduly lengthen the total time required to complete correlation.
  • the stored samples that provide the samples for the first correlation also provide the samples for the second correlation. It is desirable from a performance point of view for the second correlation to use the same samples as the first correlation, but not essential.
  • the first and second correlations may be carried out on samples which are obtained and stored at different times.
  • each of the first and second signal transmitters or detectors are particle detectors, each providing an output signal representative of particle flow at the respective detector.
  • Another possibility, however, is for there to be one signal transmitter and one signal detector; for example, the first detector may be an ultrasonic transmitter and the second detector may be an ultrasonic receiver.
  • the velocity of the flow influences the time taken for the signal from the transmitter to reach the receiver and thus the time shift between the transmitted and received signals provides an indication of flow velocity.
  • the first correlation is carried out using average output values, each derived by averaging a plurality of individual samples, and preferably by averaging four or more samples .
  • the step of averaging individual samples during the first correlation reduces the loss of information resulting from the fewer number of samples that are employed in the first correlation compared to the number that would be employed in a conventional single stage correlation and helps to ensure that the first correlation stage reaches the correct conclusion as to the approximate time shift required to give close correlation.
  • the detectors may take any suitable form but in a preferred embodiment they detect particles by detecting an electrical effect caused by the particles.
  • the electrical effect may include a triboelectric effect, although it is possible that a significant part of the effect is from other electrodynamic effects such as charges induced from charged particles passing in the vicinity of the detector.
  • the particle detectors may project into the particle flow in which case the detector may be in the form of a rod which may be of circular cross-section and may comprise an electrically conducting core which may be exposed to the particle flow or may be covered with an insulating layer which insulates the core from the particle flow. Suitable detecting arrangements are described in GB 2266772 and GB 2277154, the disclosures of which are incorporated herein by reference.
  • the particle detectors may each extend around the boundary of the particle flow and may be in the form of a ring defining a length of the passageway along which the fluid flows; such detectors are known per se .
  • the detectors may be stud sensors; that is a set of studs forming a discontinuous ring which extends around the boundary of the particle flow.
  • the invention may be applied to measuring the velocity of particles in a liquid flow but preferably the fluid is a gas and the particles are liquid or solid particles suspended in the gas.
  • the particles may be flowing along a stack and emitted through the stack.
  • a.c. components of the output signals from the detectors are used to provide the samples that are employed in the first and second correlation stages.
  • d.c. levels may be used we have found that it is advantageous when using a triboelectric detector to eliminate the d.c. component of a signal and use the a.c. component since that provides a signal more representative of particle flow.
  • consecutive samples are taken alternately from the first and the second signal transmitters or detectors.
  • the samples from the two transmitters or detectors thus span substantially the same period of time .
  • the second correlation is carried out over a range of time shifts at least four times narrower, preferably at least eight times narrower, than the range of time shifts over which the first correlation is carried out . Because the second correlation is carried out over a narrower range of time shifts it improves the resolution of the time measurement and so provides a more accurate measurement of the time shift required for close correlation.
  • the samples are subject to two stages of correlation, but it is possible for the samples to be subject to more than two stages of correlation, and in the one or more further stages the samples are then subjected to correlation over progressively narrower ranges of time shifts.
  • Such an approach can result in a reduced number of calculations but requires more complicated software for its implementation.
  • the method of correlation employed may be analogue correlation; in that case the apparatus may include an analogue-digital converter, in which the analogue signals from the probes are converted into digital represen- tations of numbers between, for example, -128 and +127.
  • the correlation data resulting from a correlation stage are normalised before the time shift required for close correlation is ascertained.
  • the method of correlation employed may be polarity correlation; in that case the apparatus may include a comparator, in which the signals from the detectors are sampled as binary values (high or low) .
  • the correlation calculation that is repeated in polarity correlation when correlating values of x and y for n samples at time shift position m is given by:
  • the Correlation Result can be said to be the bitwise Exclusive-Or of x n and y n+m .
  • the Exclusive-Or and add calculation required in polarity correlation is much quicker than the multiply and add calculation (mac) required in analogue correlation. Because of that speed increase, and the reduction in hardware complexity, previous instruments have tended to use polarity correlation.
  • the advantage of the analogue method is that although the computational requirements are more severe, if a powerful micro- processor is used, the hardware required for implementation is simpler, and so the hardware cost is lower.
  • An Hitachi Super-H processor for example, performs the mac calculation in about 150 ns .
  • the polarity correlation in hardware may be very little faster than the analogue correlation performed by a powerful microprocessor (ignoring time taken to normalise the data with the analogue method) , but the analogue correlator may be significantly cheaper and is therefore preferred.
  • the present invention also provides an apparatus for measuring the velocity of a phase of a fluid flow, - li ⁇
  • the apparatus comprising a first signal transmitter or detector at a first location in the flow, a second signal transmitter or detector at a second location in the flow downstream of the first location, at least one of the first and second signal transmitters or detectors being a signal detector, and electrical apparatus, which may include a microprocessor, coupled to the first and second signal transmitters or detectors, the electrical apparatus including storage means for storing signals associated with the transmitters or detectors, evaluating means for measuring the velocity of the phase of the flow from the sampled outputs of the transmitters or detectors, subjecting at least some of the samples of the signals associated with the transmitters or detectors to a first correlation over a relatively wide range of time shifts and then subjecting at least some of the samples to a second correlation over a relatively narrow range of time shifts selected according to the results of the first correlation stage, thereby ascertaining the time shift required of the signal associated with the second transmitter or detector relative to the signal associated with the first transmitter or detector to obtain close correlation of the signals.
  • electrical apparatus which may include a microprocessor,
  • the velocity measurement may also be combined with a particle concentration measurement enabling a measurement of mass flow to be obtained.
  • the present invention further provides a method of measuring the mass flow rate of particles in a fluid flow, the method including a method as defined above of measuring the velocity of the particles; similarly, the present invention provides an apparatus for measuring the mass flow rate of particles in a fluid flow, the apparatus including an apparatus as defined above for measuring the velocity of the particles .
  • one of the particle detectors used for measuring the velocity of the particles can also be used for measuring the concentration of the particles and certain signal processing circuitry connected to said one particle detector can be used for both purposes .
  • Fig. 1 is a sectional view of two particle detectors of a particle velocity measuring apparatus mounted in a wall of a stack through which dust particles in a flow of air are emitted;
  • Fig. 2 is a block diagram representation of an electrical system of the particle velocity measuring apparatus ;
  • Fig. 3 is a memory map representing storage of sample data in a random access memory (RAM) of the electrical apparatus of Fig. 2;
  • RAM random access memory
  • Fig. 4 is a flow diagram showing the steps involved in a correlation process carried out by the particle velocity measuring apparatus
  • Fig. 5 is a typical correlation curve generated from data from the particle velocity measuring apparatus.
  • Fig. 6 is a section of the correlation curve of Fig. 5, the curve of Fig. 6 being derived from more detailed data near the time shift required for close correlation.
  • Fig. 1 shows a first particle detector 1 and a second particle detector 2 mounted in the wall of a stack 3.
  • the particle detectors are insulated probe devices of the kind described in GB 2277154.
  • the outputs of the detectors 1, 2 are connected to electrical apparatus comprising electrical signal processing circuitry 6 and then to evaluating means comprising an analogue-digital converter 7, an input/output interface 8, external RAM 9, a Direct Memory Access Controller (DMA) 10, and a microprocessor unit 11.
  • DMA Direct Memory Access Controller
  • the apparatus just referred to processes signals from the detectors 1, 2 and, by ascertaining the time shift required for close correlation of signals from the two detectors, measures the velocity of particles in the stack. Dust particles suspended in air flowing in the stack interact with the first and second detectors 1, 2 and, as a result of electrodynamic effects, cause charging of the detectors; this is shown as Step A in Fig. 4.
  • the signals from each of the probes 1, 2 are processed by the electrical circuitry 6 in order to remove the d.c. component from each signal (Step B) .
  • the charging of the detectors and the processing circuitry for measuring the d.c. component of the signal are described in GB 2266772 and GB 2277154. The remaining a.c.
  • Step C the 8 -bit analogue-digital converter 7 which converts the magnitude of the a.c. signal into a digital signal with a value of between -128 and +127 (Step C) obtained by sampling the a.c. component at a fixed clock rate.
  • the sampled signal passes through the input/output interface 8 and is stored in external RAM 9 by the DMA 10 (Step D) .
  • the external RAM 9 takes the form of two 32 Kbyte*8 bit RAM chips which together provide 64 Kbytes of 16-bit RAM.
  • Data is acquired from the two particle detectors using an interleaved method as illustrated in Fig. 3: consecutive samples are acquired alternately from the two particle detectors.
  • consecutive samples are acquired alternately from the two particle detectors.
  • 8192 samples are acquired from each detector, but the second half of the array of samples from the first detector is disregarded, because only 4096 samples are required from the first detector for the correlation.
  • Correlation of the samples is controlled by the microprocessor unit 11, which in the particular example described is an Hitachi Super-H 32 -bit Rise processor which includes as part of the unit the Direct Memory Access Controller 10.
  • Step E For the array of samples from detector 1 and for the array of samples from detector 2, the respective average value of the array is calculated and that value is subtracted from the value of each sample within the array (Step E) . That operation removes any residual d.c. component from the samples.
  • Step F samples from each of the particle detectors are averaged in blocks of eight readings.
  • each block of eight readings comprises eight readings from the same detector that are adjacent to one another.
  • Those blocks of samples are then correlated in the internal RAM of the microprocessor 11 (Step G) ; in the particular example described, the first stage of correlation requires 512*512 macs and takes 39 ms .
  • the results of the first correlation stage are then normalised (Step H) , the process of normalisation being as described in this specification.
  • the normalised results can be represented by a correlation curve, as shown in Fig. 5 and the highest peak of the normalised correlation curve determined (Step I) .
  • the time shift corresponding to that highest peak is the time shift required to obtain a close correlation of the outputs from the first and second detectors .
  • Step J the same stored data from the particle detectors 1, 2 are subject to a second stage of correlation.
  • the second stage of correlation correlates the original samples of data individually (without averaging) , but correlates them only in a narrow window, in this particular example a window of 100 time shifts, around the time shifts at the highest peak of the correlation curve resulting from the first stage of correlation.
  • the second stage of correlation therefore requires only 100*4096 macs, taking, in principle, 61.4 ms (although implementation-related factors may increase the calculation time) .
  • the results of the second correlation stage are then normalised (Step K) .
  • the normalised results can be represented by a correlation curve and the highest peak of the normalised correlation curve determined (Step L) .
  • Fig. 6 shows the correlation curve obtained from combining the results of the second stage of correlation (between 50 and 150 on the x-axis) with some of those of the first stage (outside that area, where the resolution is reduced by a factor of eight, namely 0 to 50 and 150 to 4096 on the x-axis ; note that Fig. 6 shows only the first 400 points) .
  • the location of the peak of the correlation curve is thus determined to within one sample duration.
  • the location of the peak gives the time shift required to obtain a good correlation of the outputs from the first and second detectors.
  • the particulate velocity is obtained (Step M) by dividing the spacing of the first and second particle detectors (HeadSpacing) by the time shift (TimeDelay) required to obtain a good correlation:
  • the peak of the correlation curve occurs at position 95 on the x-axis.
  • the data from which Fig. 5 was generated was originally sampled with a 30 ⁇ s sample duration and so the time shift required for good correlation is 95*30 ⁇ s; i.e., 2.85 ms .
  • the particle velocity measuring apparatus of the particular example of the invention just described generates a particulate velocity measurement approximately twice per second. That response frequency is adequate for the monitoring of particulate velocities in many applications.
  • the invention enables analogue sampling and rapid correlation of a large number of data points (in the example described, 4096) , using a standard microprocessor rather than expensive custom-made hardware.
  • the apparatus of the particular example only requires the internal memory of the microprocessor and two 32 Kbyte external RAM chips. Fast 32 Kbyte RAM chips are available at low cost and are ideal for this application.
  • the particle velocity measuring apparatus requires no more than 64 Kbytes of RAM, avoiding the need to buy more expensive memory devices.
  • the Hitachi Super-H processor contains 8 Kbytes of internal RAM: the correlation data stores require 4096 bytes of memory, and the internal memory is also used to hold the processor working stack.
  • Data acquisition requires 16384 bytes of external RAM to store two sets of 8192 samples; processor mac operations require 4096 + 8192 16-bit locations (i.e. 12288 16-bit locations, or 24576 bytes of memory) ; the correlation result array consists of 4096 16-bit words, and two arrays are stored (i.e. 16384 bytes are required); and the normalisation factor array contains 512 normalisation factors, with each factor normalising 8 results.
  • the total memory requirement for the above operations is therefore 58368 bytes. The remaining 7168 bytes in the memory are available for the storage of other system variables.
  • the apparatus for measuring particle velocity can be combined with apparatus for measuring particle concentration to provide a mass flow meter.
  • One of the detectors 1, 2 used in the velocity measurement can also be used to provide a measurement of particle concentration as described in GB 2277154 (or if the insulated probes are replaced by ones where the electrically conducting cores of the probes are exposed, as described in GB 2266772) .
  • a particular advantage of such an arrangement is that the same electrical circuitry 6 that is connected to the detector for the velocity measurement can be used for the particle concentration measurement .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Measuring Volume Flow (AREA)

Abstract

On décrit un procédé et un appareil permettant de mesurer la vitesse d'une phase d'un écoulement de fluide dans lesquels, pour évaluer le décalage temporel nécessaire pour effectuer la corrélation fine entre un signal provenant d'un premier émetteur ou détecteur de signal et un signal provenant d'un deuxième émetteur ou détecteur de signal, on receuille et on stocke des échantillons du signal associé au premier émetteur ou détecteur et des échantillons du signal associé au deuxième émetteur ou détecteur; au moins un certain nombre des échantillons étant récupéré dans le dispositif de stockage et soumis à une première corrélation sur une plage relativement étendue de décalages temporels, alors au moins certains de ces échantillons étant récupérés dans le dispositif de stockage et soumis à une deuxième corrélation sur une plage relativement étroite de décalages temporels sélectionnés en fonction des résultats de la première étape de corrélation.
PCT/GB1998/002248 1997-07-28 1998-07-28 Mesure de la vitesse WO1999005479A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU85492/98A AU8549298A (en) 1997-07-28 1998-07-28 Velocity measurement

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9715897A GB2327761A (en) 1997-07-28 1997-07-28 Velocity measurement
GB9715897.6 1997-07-28

Publications (1)

Publication Number Publication Date
WO1999005479A1 true WO1999005479A1 (fr) 1999-02-04

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Application Number Title Priority Date Filing Date
PCT/GB1998/002248 WO1999005479A1 (fr) 1997-07-28 1998-07-28 Mesure de la vitesse

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AU (1) AU8549298A (fr)
GB (1) GB2327761A (fr)
WO (1) WO1999005479A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001079811A1 (fr) * 2000-04-12 2001-10-25 Goyen Controls Co. Pty Limited Procede et appareil pour la detection de particules dans un flux de gaz
CN110716065A (zh) * 2019-10-31 2020-01-21 湖南长城海盾光纤科技有限公司 一种基于光纤矢量水听器的流速测量系统及测量方法
WO2020030934A1 (fr) 2018-08-10 2020-02-13 Envea Uk Ltd Capteur de concentration de particules

Families Citing this family (3)

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Publication number Priority date Publication date Assignee Title
GB2390683B (en) * 2002-04-06 2005-07-06 Process Tomography Ltd Flow measurement
WO2012015898A1 (fr) * 2010-07-28 2012-02-02 Univation Technologies, Llc Systèmes et procédés pour mesurer la vitesse d'un mélange particule/fluide
GB201411701D0 (en) 2014-07-01 2014-08-13 Pcme Ltd Methods and apparatus relating to ultrasound flow probes

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WO1979001119A1 (fr) * 1978-05-25 1979-12-27 Sybron Corp Correlateur de detection de sommet
US5546006A (en) * 1994-07-01 1996-08-13 Cornell Research Foundation, Inc. Guarded capacitance probes for measuring particle concentration and flow

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WO1979001119A1 (fr) * 1978-05-25 1979-12-27 Sybron Corp Correlateur de detection de sommet
US5546006A (en) * 1994-07-01 1996-08-13 Cornell Research Foundation, Inc. Guarded capacitance probes for measuring particle concentration and flow

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Title
GOGOASA I ET AL: "AN EXTRINSIC OPTICAL FIBRE SPEED SENSOR BASED ON CROSS CORRELATION", MEASUREMENT SCIENCE AND TECHNOLOGY, vol. 7, no. 8, August 1996 (1996-08-01), pages 1148 - 1152, XP000631804 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001079811A1 (fr) * 2000-04-12 2001-10-25 Goyen Controls Co. Pty Limited Procede et appareil pour la detection de particules dans un flux de gaz
US7063731B2 (en) 2000-04-12 2006-06-20 Goyen Controls Co. Pty Ltd Method and apparatus for detecting particles in a gas flow
WO2020030934A1 (fr) 2018-08-10 2020-02-13 Envea Uk Ltd Capteur de concentration de particules
CN112771363A (zh) * 2018-08-10 2021-05-07 Envea英国有限公司 颗粒浓度传感器
CN110716065A (zh) * 2019-10-31 2020-01-21 湖南长城海盾光纤科技有限公司 一种基于光纤矢量水听器的流速测量系统及测量方法

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GB9715897D0 (en) 1997-10-01
GB2327761A (en) 1999-02-03
AU8549298A (en) 1999-02-16

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