Patent Application
20100018309
The present invention concerns fluid level measuring. More specifically, the present invention concerns a method and system for measuring the level of fluid, such as liquids and gas, in a tank using ultrasound.
Many methods and systems are known to measure the fluid level in a container including those using ultrasounds.
Some of these last techniques are based on ultrasound travelling along a waveguide including discontinuities, where variations in the waveforms along the waveguide are indicative of the liquid level.
According to other techniques, the ultrasound beam is emitted within a conduit towards the surface of the liquid and the delay to receive the echo is indicative of the distance from the source and therefore of the liquid level.
Other method and system include a single transducer mounted to the bottom of the tank so that its ultrasound beam is aimed upwardly towards the surface of the fluid.
A drawback of all known ultrasound techniques from the prior art, involving or not the use of a waveguide or conduit, is that they do not allow eliminating the limitation caused by the transducer's dead zone.
Indeed, it has been found in known techniques that a minimal distance from the bottom of the tank, which corresponds to this transducer's dead zone, cannot be measured. As it is commonly known in the art, the dead zone of an ultrasound transducer equates to the distance from the surface of the transducer to the nearest object that may be imaged. It corresponds to the ring down time of the transducer equated to distance.
In the appended drawings:
a are schematic views illustrating ultrasound sensor assemblies for measuring the fluid level in a tank according to second and third illustrative embodiments of the present invention; further illustrating the use of a reference target, the assembly of
More specifically, in accordance with a first aspect of the present invention, there is provided a method for measuring at least one fluid level in a tank including at least one fluid comprising:
emitting an ultrasound detecting beam towards a surface of the at least one fluid in the tank from a first position relative to the tank, yielding at least a portion of a path of the ultrasound detecting beam being generally perpendicular to the bottom of the tank and defining an axis intersecting the bottom of the tank; the first position being adjacent the bottom of the tank;
receiving echoes from the ultrasound detecting beam reflected from the surface of the at least one fluid in the tank at a second position biased from the first position; and
determining the at least one fluid level using the echoes received from the ultrasound detecting beam and a distance between the first and second positions.
According to a second aspect of the present invention, there is provided a sensor assembly for measuring at least one fluid level in a tank comprising:
an ultrasonic transducer assembly mounted to the tank so as to emit an ultrasound detecting beam along a path generally parallel to the bottom of the tank and for receiving ultrasound echoes incoming along the path; the ultrasonic transducer assembly being characterized by a dead zone; and
a primary reflector mounted to the tank along the path of the ultrasound beam for reflecting the ultrasound detecting beam towards a surface of the at least one fluid in the tank and for reflecting back the ultrasound echoes received therefrom; the primary reflector being distanced from the ultrasonic transducer assembly from at least the length of the dead zone of the ultrasonic transducer.
According to a third aspect of the present invention, there is provided a sensor assembly for measuring fluid level in a tank comprising:
a first ultrasound transducer mounted to the tank for emitting an ultrasound detecting beam towards a surface of at least one fluid in the tank; and
a second ultrasound transducer mounted to the tank adjacent the first ultrasound transducer for receiving ultrasound echoes from the first detecting beam reflected from the surface of the at least one fluid in the tank.
According to a fourth aspect of the present invention, there is provided a sensor assembly for measuring at least one fluid level in a tank comprising:
ultrasound emitting means for emitting an ultrasound detecting beam towards a surface of at least one fluid in the tank from a first position relative to the tank yielding at least a portion of a path of the ultrasound detecting beam being generally perpendicular to the bottom of the tank and which defines an axis intersecting the bottom of the tank; the first position being adjacent the bottom of the tank;
ultrasound receiving means for receiving echoes from the ultrasound detecting beam reflected from the surface of the at least one fluid in the tank at a second position biased from the first position; and
means for determining the at least one fluid level using the echoes received from the ultrasound detecting beam and a distance between the first and second positions.
According to a fifth aspect of the present invention, there is provided an integrated method for measuring a fluid mixture level and density in a tank including a fluid mixture comprising:
emitting an ultrasound detecting beam i) towards a surface of the fluid mixture in the tank and ii) towards a reference target in the tank from a first position relative to the tank, yielding at least a portion of a path of the ultrasound detecting beam being generally perpendicular to the bottom of the tank and which defines an axis intersecting the bottom of the tank; the first position being adjacent the bottom of the tank;
receiving echoes from the ultrasound detecting beam reflected from a) the surface of the fluid in the tank and from b) the reference target at a second position biased from the first position;
determining the fluid mixture level using the echoes received from the ultrasound detecting beam and a distance between the first and second positions;
measuring a temperature of the fluid mixture in the tank; and
using the echoes from the ultrasound detecting beam reflected from the reference target and the temperature of the fluid mixture in the tank to determine the density of the fluid mixture.
According to a sixth aspect of the present invention, there is provided a method for measuring the density of a fluid mixture comprising:
providing an identity of the fluid mixture;
measuring a temperature of the fluid mixture;
emitting an ultrasound detecting beam towards a reference target in the fluid mixture; the reference target being positioned at a predetermined distance from a transducer emitting the ultrasound detecting beam;
receiving echoes from the ultrasound detecting beam reflected from the reference target after a measured time delay after the emitting an ultrasound detecting beam towards a reference target;
using the measured time delay, the temperature of the fluid mixture and the identity of the fluid mixture, determining the ratio of at least one fluid in the fluid mixture.
The expression tank should be construed herein as including any container or recipient closed or opened for example at its top, for including fluids such as gas or liquid or a mixture thereof.
Compared with conventional ultrasound level measuring methods and systems for tank, the present method and system allow mounting the transducer inside or on the side of the tank which allows protecting the assembly from accidental contact with the road following bumps.
The device can measure multiple liquid levels of fluids such as water and fuel.
A sensor assembly for measuring the fluid level in a tank according to the present invention presents the following advantages compared with most ultrasound-based level measuring systems from the prior art using acoustic guides:
Other objects, advantages and features of the present invention will become more apparent upon reading the following non restrictive description of illustrated embodiments thereof, given by way of example only with reference to the accompanying drawings.
In the following description, similar features in the drawings have been given similar reference numerals, and in order not to weigh down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure.
A level measuring system 10 according to a first illustrative embodiment of the present invention will now be described with reference to
The system 10 is illustrated mounted to a tank 12, which is filled with a fluid in the form of a liquid 14. As will be described furtherin, a level measuring system according to the present invention can measure a plurality of levels resulting from the presence of a plurality of fluids in the tank, which can be in the form of separated gases or liquids or a combination thereof which are superimposed in the tank 12.
As will now be described, the system 10 allows measuring the level 16 of liquid 14 in the tank 12 from the bottom 18. As will become more apparent upon reading the following description, other relative height of fluid than the level 16 relative to the bottom of the tank 12 can be measured in the tank 12 by appropriately positioning the measuring system 10 in the tank 12.
The system 10 comprises a sensor assembly 19 coupled to a controller (not shown) that receives and interprets the detected signals using algorithms so as to determine the liquid level 16 in the tank 12. The controller can take many forms, from a vehicle's onboard controllers, when the tank 12 is a vehicle's gas tank, to electronic circuitry configured for that particular purpose and to which the sensor assembly 19 is connected using wires. The sensor assembly 19 can alternatively or further be coupled to the controller wirelessly. The controller can also be integral to the sensor assembly 19.
The sensor assembly 19 comprises an ultrasonic transducer 20 mounted to a side wall of the tank 12 outside thereof for emitting an ultrasound detecting beam (not shown) along a first horizontal path 22 generally parallel to the bottom 18 of the tank 12 and for receiving ultrasound echoes incoming along the path 22.
The transducer 20 is interfaced to the tank's external frame and is configured and calibrated before operation to detect through the liquid tank 12 and also to translate height into volume. Since it is believed to be within the reach of a person skilled in the art to conceive or select such a transducer, it will not be described furtherin in more detail.
The assembly 19 further comprises a reflector 24 mounted to the tank 12 along the path 22 of the ultrasound beam for reflecting the ultrasound detecting beam towards the surface 26 of the liquid 14 and for reflecting back to the transducer 20 along the path 22 the ultrasound echoes received from the surface 26 and indicative therefrom.
The expression “path” should be construed herein as including the field of view of the transducer 20 as allowed by the assembly 19. It should not be construed as meaning that the ultrasound detecting beam and the returning ultrasound echoes necessarily follow a same course in opposite direction for example.
The reflector 24 is sufficiently distanced from the ultrasonic transducer 20 to compensate for the dead zone which characterizes the ultrasonic transducer 20. The distance between the reflector 24 to the transducer 20 allows sufficient time for the transducer 20 to become sensitive after the emission of the burst of signals.
It is to be noted that, for illustrative purposes, the dimensions of the transducer 20 and reflector 24 have been exaggerated in
The reflector 24 can take any form including a portion of a body having a 45 degrees angle made of a material that reflects ultrasounds in the fluid. The reflector 24 can be mounted to the tank 12 independently of the transducer 20 or can be assembled to the transducer 20 to form a single device that is secured to the tank 12.
The reflector 24 acts as a folding element for the ultrasound beam and for the echoes reflected from the fluid interface 26. The use of the reflector 24 allows detecting minimal levels which can be very low relatively to the bottom 18 of the tank 12, by allowing the ultrasound beam to extend parallel to the bottom 18 of the tank 12. According to the sensor assembly configuration shown in
Even though the system 10 includes a reflector 24 provided with a 45-degrees angle that causes the beam to be reflected at 90 degrees from its initial path 22, a system for measuring fluid level in a tank according to the present invention is not limited to such a reflector. According to a further illustrative embodiment (not shown), a reflector configured to reflect the ultrasound beam at another angle is provided. Generally stated, the sensor assembly can be provided with one or more reflector that yields an acoustic beam path adapted for the container and fluid therein. For example, the system can be configured to yield a beam path which includes a plurality of direction changes, which can be advantageous where the tank shape is irregular such as in modern fuel tanks. The first reflector can be seen as a primary reflector and any further reflector can be seen as secondary reflectors.
The reflector 24 can further act in some application as an element to shape the beam angle. It can also be used as a collector for the returning beam.
In summary, the following method 200 is implemented in the system 10 to measure the fluid level 16 in the tank 12:
202—an ultrasound detecting beam is emitted towards the surface 26 of the fluid 14 in the tank 12 from a first position 30 relative to the tank 12 so as to yield a portion of a path of the ultrasound detecting beam which is generally perpendicular to the bottom of the tank 12 and which defines an axis intersecting the bottom of the tank 12. The first position 30 is defined by the surface of the reflector 24 where the detecting beam is reflected;
204—receiving echoes from the ultrasound detecting beam reflected from the surface 26 of the fluid 14 in the tank 12 at a second position 32 biased from the first position. The second position 32 is defined by the ultrasound transducer's face; and
206—determining the fluid level using the echoes received from the ultrasound detecting beam and the distance between the first and second positions 30 and 32.
As mentioned hereinabove, the first position 30 is adjacent the bottom of the tank 12.
In step 206, the controller measures the time required for the sound waves to propagate from the transducer 20 to the plane where the liquid interfaces with the gas or with another fluid above it or to the container wall depending on the application, the configuration of the tank 12 and/or the level of fluid 14 therein. In the example illustrated in
The fluid level 16 is determined based on the speed of sound in the fluid 14 and the net travel time in the vertical path 28. The horizontal paths 22 are eliminated in the calculations, which are done by the controller.
Even though the transducer 20 is illustrated in
The transducer can also be mounted in the tank 12 encapsulated in a sealed housing (not shown). The reflector 30 is of course submerged completely in the tank 12. In some application, a partially submerged reflector 30 can be provided. In the case where the tank 12 does not include a corrosive fluid or wherein the transducer or the housing it is encapsulated in is resistant to the corrosive material, the transducer 20 may be directly submerged in the fluid while the rest of the system remains as described above.
A sensor assembly 36 for measuring the fluid level in a tank according to a second illustrative embodiment of the present invention will now be described with reference to
In addition to the ultrasonic transducer 20, which is mounted to the tank side wall 38 outside thereof, and to the reflector 24, operatively mounted as described hereinabove with reference to
The reference target 40 is in the form of a body or object mounted to the floor 18 of the tank 12 and/or to the reflector 24 so as to be positioned along the path 22. The target 40 is sufficiently small so as not to block the ultrasound beam from the transducer 20. It is also located beyond the transducer 20 dead zone.
According to the second illustrative embodiment, the reference target is slidably mounted to the floor 18 of the tank 12 via a rail 43 so that its distance 44 relatively to side wall 38 of the tank 12 and therefore to the transducer 20 can be modified.
The reference target 40 allows calibrating the system 42 for the speed of sound in the fluid or fluid mixture contained in the tank 12. As it is believed to be well known in the art, the speed of sound in the tank may vary with the fluid temperature, the nature of the fluid or mixture or with any other parameters which contribute to the change of speed of sound in the fluid. Since any of these parameters may vary over time, an initial calibration can be executed while doing any fluid level measurements in the tank, using the reference target 40 and then further calibrations can be done at fixed or variable intervals to cope for changes in the shape of the tank 12 for example.
The target 40, the reflector 24 and/or the transducer 20 can be assembled or be part of a single device or body so as to reduce the number of components in the system 42 and also for ease of installation or be mounted independently to the floor of the tank 12 or to a pump installed inside the tank 12. Also, similarly to what has been discussed with reference to the sensor assembly 10, the assembly 36 can be mounted to the tank 12 at another position than to or adjacent the bottom thereof so as to measure the height of fluid relatively to another reference.
The echoes reflected back from the target 40 and the delay between the emission of the ultrasound beam from the transducer 20 and the corresponding returned echoes can be used by the controller to calculate further information when known parameters are fed to the controller.
For example, when a plurality of known fluids is mixed in the tank, the identity of the fluid mixture ratio can be determined providing the following parameters: the speed of sound for different mixture ratios, the distance 44 of the reference target 40 to the transducer 20 and the mixture temperature, which can be determined by adding a thermometer in the tank for example.
For example, to measure the content of Ethanol in the gasoline, the speed of sound in the mixture depends on the percentage of Ethanol in the mixture. It also depends on the mixture temperature. Therefore providing the temperature, the time of flight to the reference target and the distance 44, the speed of sound and the ratio can be calculated by the controller.
Conversely, the temperature of a known fluid or fluid mixture in the tank can be computed by the controller, providing the distance 44 of the reference target 40 to the transducer 20 and knowing the ratio in the mixture.
As a person skilled in the art will now appreciate, providing a reference target 40 between the transducer and the reflector 24 allows the calibration of the ultrasound flight time to the reflecting surface 26 with regards to the nature of the fluid and the average fluid temperature as mentioned hereinabove.
In certain application the reflector 24 can be used as a reference target and so is a tank wall.
A self calibration technique similarly to the one described in U.S. patent application Ser. No. 11/029,415, titled “Method and System for Measuring Fluid Level in a Container”, naming Agam et al. as the inventors and published on Aug. 3, 2006 under No. US-2006-0169055-A1, which is incorporated herewith by reference, can further be implemented in the controller. The use of a ‘wave guide’, which is described in the '415 application is of course not required in a method and system according to the present invention.
According to a further illustrative embodiment (not shown), the transducer 20 can be replaced by a couple of transducers mounted to the tank side by side similarly to the transducer 20. The couple of transducers include an emitter for sending an ultrasound detecting beam towards the target 40 and the reflector 24 and a receiver for collecting echoes reflected therefrom.
According to third illustrative embodiment of an ultrasound sensor assembly from the present invention (see
In addition to the transducer 20 and reflector 24, the ultrasound sensor assembly 46 further includes a beam shaper and collector such as a beam expander that increases the ultrasound energy collected, yielding a wider beam 48 downstream from the reflector 24.
Increasing the beam size downstream from the reflector 24 causes a plurality of echoes resulting from a single ultrasound detecting beam to reflect from the surface 26 of the fluid 14. As illustrated in
Even though the beam expander is illustrated in
In further illustrative embodiment, the beam shape transformer is in the form of a beam focusing element or device (not shown).
As can be seen in
The assembly 54 comprises an ultrasound transducer 20 provided with a collecting aperture 56, which can be in the form for example of an ultrasound horn operatively mounted to the transducer 20 to increase or decrease the width of the ultrasound detecting beam 58 and increase the collecting cross-section of the transducer thereof, 24.
Since ultrasound horns are believed to be well-known in the art, they will not be described furthering in more detail.
Even though a calibration target, such as the target 40 is not illustrated in
As will now become apparent with reference to further illustrative embodiments of the present invention, numerous other variations in the ultrasound sensor assembly are possible within the scope of the present invention, allowing for example to minimize the detection limitation inherent to the dead zone.
In
The assembly 60 comprises two side by side transducers 66-68 and a combined reflector/target assembly 70. The two transducers 66-68 are mounted to the side of the tank (not shown) outside thereof. A first one of the two transducers 66-68 acts as an ultrasound emitter 66 that emits an ultrasound detecting beam 72 along a first horizontal path 74. The second transducer is an ultrasound receiver 68 for receiving ultrasound echoes reflected from the fluid only along a second path 76 parallel to the first path 74. This approach also allows elimination of the dead zone while allowing the calibration to take place.
The combined reflector/target assembly 70 is mounted to the tank along the paths 74-76 for reflecting the ultrasound detecting beam towards the surface 26 of the fluid 14 and for reflecting back to the transducer 68 the ultrasound echoes received from the surface 26 and indicative therefrom along the path 76. The assembly 70 includes a target portion 78 and a reflector portion 79. The target portion 78 is in the line of sight of the emitter 66.
In operation of the assembly 60, the ultrasound emitter 66 emits an ultrasound beam towards the reflector assembly 70 which reflects the beam towards the fluid surface or interface 26. The echoes reflected from the interface 26 are reflected back to the receiver 68, which is positioned adjacent the emitter 66.
The echoes indicative of the target portion 78 received by the transducer 66 can be used to calibrate the system for the difference in the speed of sound, due for example to a change in the fluid mixture as explained hereinabove. In addition to the assembly 60, the system includes a controller as described hereinabove.
Since the sensor assembly 80 is similar to the assembly 19, and for concision purposes, only the differences between the two assemblies 19 and 80 will be described herein in more detail.
The assembly 80 includes a second transducer 82 capable of emitting and receiving ultrasounds positioned adjacent the first transducer 20. Both transducers 20 and 82 are mounted in the tank (not shown) and secured to the bottom (not shown) thereof. The transducers 20 and 82 are both sealed. They can be assembled in a single casing or independently secured to the tank.
The operation of the transducer 20 in relation to the reflector 24 is as described with reference to
The assembly 80 further includes a calibration target 84 similar to the target 40 (see
The assembly 90 comprises a first transducer 92, acting as an ultrasound emitter, and a second transducer 94, acting as an ultrasound receiver. The first and second transducers are mounted side by side adjacent one another and oriented towards the expected fluid interface 26 so that reflections caused by the ultrasound detecting beam 96 onto the interface 26 are within the field of view 98 of the second transducer 94.
The assembly 90 further includes a target 100 secured to the tank wall (not shown) or to the first or second transducer 92 or 94 for calibrating the system for the variation in the speed of sound in the fluid 14 as described hereinabove. The target 100 can be omitted when such calibration is not required by the application. The first and second transducers 92 and 94 are secured to the tank wall outside or inside thereof. They are either encased together or independently secured to the tank.
It is to be noted that the sensor assemblies 36, 46, 54, 60, 80 and 90 all operates under the method 200 described hereinabove.
The sensor assembly 106 is identical to the assembly 90 with the following exceptions: the target 100 is omitted and a thermistor 108 is further provided. However, as will become more apparent upon reading the following description, the density meter can be used as a stand-alone application or part of a fluid level sensor assembly, such as the assemblies 19, 36, 46, 54, 60, 80 and 90.
The sensor assembly 106 and the thermistor 108 are both secured to the raised floor 110 of an enclosure 111, which further includes first and second opposite openings 112-114 respectively defining an inlet and an outlet for the fuel in the enclosure 111. The enclosure 111 and more specifically the wall of the floor 110, which protects the transducer 106 and in some applications the controller, is made of a hard material, such as such as stainless steel. In addition to protect the sensor 106 and the electronic not shown) from suffering corrosion by the fluid, the wall 122 of the enclosure 111 is used as a calibration target.
The thermistor 108 and the transducers of 92-94 of the sensor assembly 106 are coupled to a controller (not shown) via connectors 116 or using conventional wireless devices. Since such devices are believed to be well known in the art, and for concision purposes, they will not be described furtherin in more detail.
The enclosure 111 may be mounted to the pipe 102 via its inlet and outlet 112-114 through clamps 118 so that the enclosure defines an enlarged section of the pipe 102. Other alternative or further means can be used to mount the enclosure 111 to the pipe 102.
Other means than a raised floor can be used to protect the transducers 92-94, thermistor 108 and/or electronics from the liquid or fluid in the enclosure 111. These components can also be simply mounted to the enclosure 111 outside thereof or be mounted in a protective box (not shown) in the enclosure 111.
In operation, the enclosure 111 is filled by the fluid as it travels in the pipe 102 (see arrows 120). The thermistor 108 measures the temperature of the fluid in the enclosure 111 and the controller measures the time for an ultrasound pulse emitted by the emitter 92, which is reflected on the surface 122 of the enclosure facing the face of the transducer to return to the sensor assembly 106. The measured time of flight allows calculating the speed of sound providing the mixture temperature. This information and the identity of the fluids which compose the mixture is used by the controller (not shown) to calculate the ratio of the mixture ingredients.
A sensor assembly 124 for measuring the fluid level in a tank according to a tenth illustrative embodiment of the present invention will now be described with reference to
The sensor level switch assembly 124 includes an ultrasonic transducer 126 mounted to the side tank 12 outside thereof for emitting an ultrasound detecting beam 128 along a first horizontal path generally parallel to the bottom 18 of the tank 12 and for receiving ultrasound echoes incoming along the same path.
The transducer 126 is interfaced to the tank's external frame and is configured and calibrated before operation to detect through the liquid tank 12. The transducer 126 is so secured to the tank 12, relatively to the bottom 18, at the level that one wishes to detect.
In operation, the transducer 126 produces a different signal depending on whether the detecting beam 128 travels in a first fluid 130, which can be for example a liquid, in a second fluid 132, which can be for example air or another gas or in the interface between the two fluids 130-132. Providing the nature of the fluids in the tank 12, and the corresponding ultrasound signature, the transducer 126 can act as a digital level sensing switch for these fluids. It is to be noted that the above-described digital level sensing method does not result in any measurement limitation resulting from the dead zone.
Also, as can be seen in
It is to be noted that the number of such digital level sensing switches may vary and so are their positions along the height in the tank 12. Also the controller (not shown) may be configured to recognize the signal signature of one or a plurality of fluids in the tank 12 so that each switch can be triggered when the level of a selected one or a plurality of fluids reach the level of the switch.
Each of the transducers 126 can be coupled to an individual controller (not shown) configured to receive and analyze the signal from the transducer 126 connected thereto to determine whether the nature of the fluid across the corresponding path 134, 136 or 138 has changed since the last measurement or all transducers 126 can be coupled to a single controller (not shown) configured to receive the signals from all three transducers 126 for similar treatment. Of course, in that later case, the controller allows associating a particular signal received to a corresponding transducer.
The transducers 126 can also be inserted in the tank 12. More specifically, as can be seen in
Systems for measuring fluid level in a tank provided with any one of the sensor assemblies illustrated in
Also, any of the above-described systems including digital level sensing switch can further include a reference target (not shown) such as the target 40 in
It is to be understood that the invention is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The invention is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the present invention has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope and nature of the subject invention as defined in the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2008/000330 | 2/20/2008 | WO | 00 | 9/18/2009 |
| Number | Date | Country | |
|---|---|---|---|
| 60890939 | Feb 2007 | US |
