GB2256049A - Measurement of flocculation layer depth and density - Google Patents
Measurement of flocculation layer depth and density Download PDFInfo
- Publication number
- GB2256049A GB2256049A GB9210802A GB9210802A GB2256049A GB 2256049 A GB2256049 A GB 2256049A GB 9210802 A GB9210802 A GB 9210802A GB 9210802 A GB9210802 A GB 9210802A GB 2256049 A GB2256049 A GB 2256049A
- Authority
- GB
- United Kingdom
- Prior art keywords
- density
- particles
- layer
- solid
- signals
- 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- Withdrawn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
-
- 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
- G01F23/22—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 measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—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 measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2962—Measuring transit time of reflected waves
-
- 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
-
- 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
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/222—Constructional or flow details for analysing fluids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/24—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing the transmission of wave or particle radiation through the material
-
- 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
- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/011—Velocity or travel time
-
- 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
- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/015—Attenuation, scattering
-
- 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
- G01N2291/024—Mixtures
- G01N2291/02416—Solids in liquids
-
- 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
- G01N2291/028—Material parameters
- G01N2291/02818—Density, viscosity
-
- 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
- G01N2291/028—Material parameters
- G01N2291/02836—Flow rate, liquid level
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Biochemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Acoustics & Sound (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
Sonar echo ranging is used to determine flocculation layer 13 particle density in e.g. a water clarifier. The amount of reflected signal can be used to determine the particle density, and taking account of the reflection time, the respective densities of the layer and the supernatant liquid layer 16. Depth can be determined from the reflection times. Logarithmic and averaging techniques may be used. The flocculation layer is typically of low density. <IMAGE>
Description
MEASUREMENT OF PARAMETERS OF LIOUID/SOLID SYSTEMS
This invention concerns a method and apparatus for sensing the depth and/or other parameters of solids in a liquid.
Clarifier tanks are used in the preparation of potable water to settle suspended solid matter into a concentrated sludge which can be readily disposed of. A large tank is used and water enters at or near the bottom from a series of spaced inlet apertures. The water rises slowly in the tank to the surface and overflows into run-off channels. Suitable electrochemicals are added to the raw water feed to encourage the suspended solids matter therein to collect into "floc" particles by electrostatic action.
These particles are denser than the surrounding water and settle towards the bottom of the tank. One or more outlets are provided in the lower part of the tank to draw off the floc layer or blanket from the tank. The drawn-off water containing floc particles is then left to settle so that the floc particles form a dense sludge.
The floc particles falling against the rising current of water in the tank grow in a complex way which results in a fairly distinct upper boundary to the floc layer or blanket. To operate the tank efficiently, this boundary must not be allowed to rise near to the surface of the tank, since otherwise there is a substantial risk of the solids getting into the run-off channels and so contaminating the outflow. In the past, attempts to monitor the position of the blanket surface or to warn of danger levels have usually necessitated the immersion in the tank of sensitive instruments, and these instruments have suffered over a period of time from contamination and from weed and algae growth on sensitive surfaces.
We have now found another way of sensing the depth of the solids blanket surface in the tank using a sonar echo ranging technique.
Sonar echo ranging techniques have been used in the past for sludge level measurement in waste water treatment. The level of the sludge layer is determined from the volume reverberation of the water/sludge system rather than reflection from an individual target. Reverberation is a general term for the amount of signal scattered back from a large number of small targets in the water. In earlier echo sounder/sonar systems reverberation was generally regarded as unwanted noise. It will be appreciated that in a liquid/solid system of this type, the density of the sludge is relatively large (typically several grams per litre of water) and there is a fairly well defined boundary between the sludge layer and the clearer water above.
The present invention is based on the discovery that sonar echo ranging can also be used to measure the properties of a system of solid particles in a liquid in which the solid concentration is relatively low. In a potable water clarifier, the floc blanket typically has a density of solid particles of less than one gram per litre.
Thus, a first aspect of the present invention relates to the measurement of the depth of a blanket layer of solid particles in a liquid/solid system in which the particle density is relatively low.
A first aspect of the present invention provides a method of clarifying potable water including the step of allowing solid particles in the water to settle into a layer, comprising directing acoustic signals through the liquid, detecting acoustic signals reflected from the solid particles in the layer, and determining the depth from the time taken for the signals to be scattered or reflected back from the layer.
We have also discovered that sonar echo ranging can be used to measure the density of particles in a liquid/solid system, such as the density of a floc layer or the sludge in a settling tank. Thus a second aspect of the invention relates to the measurement of density of solids in a liquid Using sonar echo ranging. In a second aspect, the present invention provides a method of determining the density of. solid particles in a liquid comprising directing acoustic signals through the liquid, detecting acoustic signals reflected from the particles and determining the density of the particles from the proportion of the generated signals which are scattered or reflected by the particles.
Consider for example a floc blanket in a clarifier tank as described above. The blanket itself will cause a peak in the amplitude of reflected sonic waves preceded by a slope due to some back scattering or reverberation from individual particles at the edge of the blanket. The height of the peak is a measure of the density of the blanket, whilst the position of the peak is a measure of its depth.
The density of the supernatant liquid can also be measured in the same way. For example, in the aforementoned floc blanket system, the level of the reflected signals preceding the slope due to the front of the blanket will depend on the concentration of impurity particles above the blanket. Measurement of the density of particles in the supernatant liquid is particularly useful for ensuring that flocs do not pass into the clear outflow.
A particular advantage realised by this invention is that the same instrument and the same set of measurements enables several parameters of a system to be determined.
Hitherto only sludge depth has been measured and all other information has been disregarded. For example, in a floc blanket water treatment system, reverberation measurement can be used to determine the concentration of particles in the supernatant liquid, the density of the blanket itself, and possibly the concentration of impurities in the incoming liquid as well as the depth of the blanket. Thus, a third aspect of the invention relates to the use of sonic waves to determine a plurality of parameters of a liquid/solid system.
It will be appreciated that the present invention has numerous applications apart from that described above.
In water treatment, the invention can be used to monitor desludging as well as chemical dosing. However, the invention is useful in general for the determination of concentration or density of solids in a liquid in any technical field.
In the preferred embodiment of the invention, several samples of individual echoes or reflections are taken and averaged in order to obtain a repeatable characteristic showing the average reverberation pr echo from each level in the tank. Such averaging techniques are known in the art for determining sludge depth. In the preferred embodiment the linear averaging technique is extended to the whole signal trace to determine other parameters of a liquid/solid system.
An embodiment of the invention will now be described in detail by way of example only with reference to the accompanying drawings in which:
FIGURE 1 is a schematic vertical view of echo sounder positioned in a clarifier tank for carrying out the present invention;
FIGURE 2 is a schematic block diagram of the circuitry used to generate and record sound waves;
FIGURE 3 is a graph showing idealised results of echo amplitude versus range obtained using a linear detector; and
FIGURE 4 is a graph showing idealised results of echo amplitude versus range obtained using a logarithmic detector.
Figure 1 shows a clarifier tank 10 for use in purifying water. Water to be purified and to which floculation inducing chemicals have been added enters at the bottom of the tank via inlet 11. Clear water is lead away via outlet channels 12. In use, the incoming water rises up through a blanket layer 13 where the particles in the new water are coming together, or floculating, into larger groups and attaching themselves to "flocs" which are already present. In a well set up tank, the flocs form a blanket with a well defined boundary.
Means for decanting off the floc blanket are provided lower down in the tank. In this embodiment of the invention, these means comprise a pair of conical hoppers or desludging cones 14 in which the flocs can settle and become more concentrated before being run off via outlet pipes 15.
Above the blanket is a volume 16 of much cleaner water but with a low remaining density of small particles and individual flocs. This clear water overflows into the outlet channels 12.
The efficient operation of a clarifier depends critically on the blanket density and stability. The technique to be described below enables both of these parameters to be measured as well as the effluent water quality, using a single measuring instrument.
The instrument includes one or more ultrasonic transducers 20 shown positioned just below the surface of the effluent water for emitting ultrasonic waves into the water.
Figure 2 shows an arrangement including two transducers 21,22, one for transmitting and one for receiving, although it will be appreciated that one transducer could perform both functions. Signals from an oscillator 23 are applied to the transducer 21 via gating circuitry 24 controlled by a timer 25, and an amplifier 26 so as to generate short bursts of electrical signals at a particular frequency, suitably between 0.2 and 5 Mhz. The burst is repeated at regular intervals as set by the timing circuit 25 and the pulse length is arranged to give the spatial resolution needed for the measurements to be made in the tank, usually around 50 mm.
The returned acoustic echo is picked up by transducer 22 which converts it into an electrical signal.
This signal appears noise-like because it is the sum of the echoes from a very large number of scattering particles and these echoes have random phases and amplitudes.
The electrical signal is amplified by an amplifier 27 and passed through a band pass filter 28 centred on the transmitter frequency. The amplifier 27 may have a constant gain or be automatically adjusted during each receive period to correct for the transmission loss. The filter 28 is selected to have a sufficient bandwidth to pass the pulse with little distortion. It also serves to reduce the electrical noise power generated in the amplifier which passes to the detector stages 29.
Either a linear or a logarithmic detector (rectifier) can be used, the logarithmic detector being more convenient as it works over a wider dynamic range. The detected signal is converted to digital data in the conventional manner by sampling at intervals of a small fraction of the duration of the transmitted pulse, under the control of timer 25. This sequence of digitised samples is stored in a memory circuit which forms part of a signal averager indicated at 30.
After a single transmission, the digitised signal reveals little information on the echoes returned from any level within the tank, due to noise which is present.
However, if a number of samples of individual echoes are averaged, this averaged echo smooths out to give a repeatable characteristic showing the average reverberation, from each level in the tank. The technique of linear averaging to measure reverberation coefficients is already well known and will not be described in detail herein. We have found that this technique works well with a logarithmic or linear detector.
Figures 3 and 4 show rather idealised versions of the reflection amplitude versus tank depth traces obtained using linear and logarithmic detectors respectively. This shows a section near the surface between Do and D1 of small echoes, then a sharp rise at the front of the blanket between D1 and D2 followed by a slope down again from D2 to
D3. For a linear system the slope down is more or less exponential and hence linear for the logarithmic detector.
After this there is a short but steep "spike" at D4 which is the echo from the bottom of the tank.
The data from this trace may be used to determine the depth of the floc blanket, the density of the blanket and the concentration of impurity particles in the volume of clear water 16. The level of the averaged signal between
Do and D1 is indicative of the concentration of the particles in the clear water above the blanket. The height of the peak at D2 gives a measure of the blanket density.
The higher the peak, the more dense is the blanket. The time delay before the steep rise at D1 occurs can be converted to the depth of the blanket from knowledge of the velocity of sound in water.
It should be noted that in known measurement techniques using ultrasound in liquids, the ripples at the front of the trace have been disregarded as unwanted noise.
Previous density measurement techniques using ultrasound have used velocity measurement and measurement of sound resonance in order to determine density or concentration.
The slope at the back of the blanket echo is caused by the attenuation coefficient of the ultrasound in water. In a typical clarifier at a water treatment works, the density of the blanket is low enough that the attention is in fact very close to that for pure water at the same temperature. However, when the instrument is applied to a more substantial blanket in other water treatment applications, the slope will vary with the density of the blanket and can be used as a further measure of this parameter.
It will be appreciated that the apparatus and method described above can be used in many applications apart from water treatment processes. Also, the same instrument as that described above can be used to determine the level and density of sludge in a hopper where this is used to concentrate it before removal. As well as desludging, the invention can be used in chemical dosing processes. A particularly advantageous feature of the invention is that a single instrument and a single operation of the instrument can be used to determine blanket depth and density and density of the supernatant liquid.
Claims (10)
1. A method of determining the density of solid particles in a liquid comprising directing acoustic signals through the liquid, detecting acoustic signals reflected from the particles and determining the density of the particles from the proportion of the generated signals which are scattered by the particles.
2. A method as claimed in claim 1 for determining density in a solid/liquid system in which some of the solid particles have formed a "blanket" layer and some solid particles are present in the supernatant liquid, the method comprising determining the depth of the particles from the time taken for signalS to be scattered back from those particles, and using the depth to determine, separately, the density of solids in the superatant liquid and the density of particles in the blanket.
3. A method as claimed in claim 1 or claim 2 for determining density in a solid/liquid system in which some of the solid particles have formed a "blanket' layer and some solid particles are present in the supernatant liquid, the method further comprising determining the depth of the blanket from the time taken for the amount of scattered signal to rise sharply.
4. A method of determining the depth of a layer of solid particles in a liquidí solid system, the solids being present in a concentration of less than 1 gram/litre, comprising directing acoustic signals through the liquid, detecting acoustic signals reflected from the solid particles in the layer, and determining the depth from the time taken for the signals to be scattered back from the layer.
5. A method of clarifying potable water including the step of allowing solid particles in the water to settle into a layer, wherein the density of the supernatant liquid and/or the layer and/or the layer depth is determined by the method of any of claims 1 to 4.
6. A method as claimed in any preceding claim in which the amount of reflected signals is recorded as a function of the time delay from generation of the signals
7. A method as claimed in claim 6 in which the signals are generated in successive bursts and the solid layer density and/or solid layer depth and/or density of supernatant liquid are determined fro the average reflection determined'from several signal bursts.
8. A method as claimed in any preceding claim in which the scattered signals are detected by a linear detector.
9. A method as claimed In any ot claims 1 to 7 in which the scattered signals are detected by a logarithmic detector.
10. A method of determining the parameters of a solid/liquid system sklbstantLally as hereinbefore described with reference te the accompanying drawings
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB919111011A GB9111011D0 (en) | 1991-05-22 | 1991-05-22 | Water treatment apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9210802D0 GB9210802D0 (en) | 1992-07-08 |
| GB2256049A true GB2256049A (en) | 1992-11-25 |
Family
ID=10695389
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB919111011A Pending GB9111011D0 (en) | 1991-05-22 | 1991-05-22 | Water treatment apparatus |
| GB9210802A Withdrawn GB2256049A (en) | 1991-05-22 | 1992-05-21 | Measurement of flocculation layer depth and density |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB919111011A Pending GB9111011D0 (en) | 1991-05-22 | 1991-05-22 | Water treatment apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB9111011D0 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19648236A1 (en) * | 1996-11-22 | 1998-05-28 | Kathoefer Ets Gmbh | Method and device for determining material properties of liquids |
| WO1998048248A1 (en) * | 1994-04-26 | 1998-10-29 | Cytec Technology Corp. | Settling process analysis device and method |
| EP0901020A2 (en) * | 1997-05-23 | 1999-03-10 | Dr. Bruno Lange GmbH | Apparatus and device for determining the level of sludge in a settling tank |
| US5939622A (en) * | 1994-04-26 | 1999-08-17 | Cytec Technology Corp. | Settling process analysis method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1599067A (en) * | 1978-05-30 | 1981-09-30 | Energy Secretary Of State For | Ultrasonic testing |
| US4542644A (en) * | 1983-09-26 | 1985-09-24 | The United States Of America As Represented By The United States Department Of Energy | Void/particulate detector |
| US4739662A (en) * | 1982-06-11 | 1988-04-26 | Micro Pure Systems, Inc. | Ultrasonic particulate sensing |
-
1991
- 1991-05-22 GB GB919111011A patent/GB9111011D0/en active Pending
-
1992
- 1992-05-21 GB GB9210802A patent/GB2256049A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1599067A (en) * | 1978-05-30 | 1981-09-30 | Energy Secretary Of State For | Ultrasonic testing |
| US4739662A (en) * | 1982-06-11 | 1988-04-26 | Micro Pure Systems, Inc. | Ultrasonic particulate sensing |
| US4542644A (en) * | 1983-09-26 | 1985-09-24 | The United States Of America As Represented By The United States Department Of Energy | Void/particulate detector |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998048248A1 (en) * | 1994-04-26 | 1998-10-29 | Cytec Technology Corp. | Settling process analysis device and method |
| US5939622A (en) * | 1994-04-26 | 1999-08-17 | Cytec Technology Corp. | Settling process analysis method |
| AU733464B2 (en) * | 1994-04-26 | 2001-05-17 | Cytec Technology Corp. | Settling process analysis device and method |
| DE19648236A1 (en) * | 1996-11-22 | 1998-05-28 | Kathoefer Ets Gmbh | Method and device for determining material properties of liquids |
| EP0901020A2 (en) * | 1997-05-23 | 1999-03-10 | Dr. Bruno Lange GmbH | Apparatus and device for determining the level of sludge in a settling tank |
| EP0901020A3 (en) * | 1997-05-23 | 2001-04-11 | Dr. Bruno Lange GmbH & Co. KG | Apparatus and device for determining the level of sludge in a settling tank |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9210802D0 (en) | 1992-07-08 |
| GB9111011D0 (en) | 1991-07-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0454821B1 (en) | Velocity measurement system | |
| CA1296094C (en) | Filling level meter | |
| AU646353B2 (en) | Velocity measurement system | |
| US6062070A (en) | Method and apparatus for the sonic measurement of sludge and clarity conditions during the treatment of waste water | |
| US4489601A (en) | Apparatus and method of measuring the level of a liquid | |
| US4763525A (en) | Apparatus and method for determining the quantity of gas bubbles in a liquid | |
| US4121094A (en) | System for detecting, indicating and regulating the level of semi-solid matter in a reservoir | |
| Gallagher et al. | Performance of a sonar altimeter in the nearshore | |
| US5635632A (en) | Settling process analysis device and method | |
| US6044703A (en) | Settling process analysis device and method | |
| US5421211A (en) | Liquid flowmeter including doppler signal processing, and method | |
| DE59608976D1 (en) | METHOD AND DEVICE FOR DETERMINING A LIQUID HEIGHT WITH THE AID OF ULTRASOUND IMPULSES | |
| US3795893A (en) | Doppler speed log | |
| JPS63103962A (en) | Method and device for measuring volume retention rate of dispersed phase in liquid/liquid dispersed system by ultrasonic wave | |
| GB2256049A (en) | Measurement of flocculation layer depth and density | |
| US3805224A (en) | Method and apparatus for monitoring biological activity | |
| US5789676A (en) | Settling process analysis device and method | |
| JPH01304322A (en) | Instrument for measuring boundary of suspended matter | |
| JP2001183354A (en) | Ultrasonic concentration meter | |
| Kimura et al. | A high resolution ultrasonic range measurement method using double frequencies and phase detection | |
| JP2854423B2 (en) | Interface device for suspended foreign matter | |
| Seibt-Winckler et al. | Measurements with a three frequency echo sounder for the detection of suspended matter in a river estuary | |
| GB2359134A (en) | Signal processing apparatus for radar or sonar systems | |
| JPH06174530A (en) | Ultrasonic distance measuring apparatus | |
| CN115560827A (en) | Interface sensor and operation method of interface sensor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |