CN114046857A - Anti-inclination and anti-fluctuation ultrasonic liquid level sensor and application and processing method thereof - Google Patents
Anti-inclination and anti-fluctuation ultrasonic liquid level sensor and application and processing method thereof Download PDFInfo
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- 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
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- 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
- G01F23/30—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 floats
- G01F23/64—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 floats of the free float type without mechanical transmission elements
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Abstract
The invention provides an anti-inclination and anti-fluctuation ultrasonic liquid level sensor and an application and processing method thereof.
Description
Technical Field
The invention belongs to the technical field of liquid level measurement, and particularly relates to an anti-inclination and anti-fluctuation ultrasonic liquid level sensor and an application and processing method thereof.
Background
Liquid level sensors that measure liquid level using the time difference between transmission and reflection of ultrasonic waves have been widely used in the field of measurement and control technology. The current common technical schemes are two types:
1. the ultrasonic sensor is arranged above the liquid to be detected, the ultrasonic wave reaches the liquid level through the air, and no obstacle exists in the middle. The liquid level is measured by the time difference between the emission and reflection of the ultrasonic waves in the air. The advantage of this solution is non-contact measurement, but the limitations in use are: firstly, when the air is close to 0 ℃, the piezoelectric sheet generating and receiving ultrasonic waves frosts, so that the measurement is invalid; secondly, when the surface of the liquid to be measured fluctuates and the liquid container inclines, the reflection path of the reflected wave deviates from the defined measurement line, so that the measurement result has large error and even fails. The sensor is generally applied to the situation that the ground is fixed and the temperature is normal temperature.
2. The ultrasonic sensor is arranged at the bottom in the measuring cylinder, the length of the measuring cylinder is slightly larger than the maximum height of the liquid level, and the ultrasonic sensor is not provided with a floater tracking the liquid level. The measuring cylinder is vertically arranged at the bottom of the measured liquid in use, and the liquid level is measured by utilizing the time difference of the ultrasonic wave emitted from the bottom of the liquid to the liquid level surface for reflection. The scheme is generally used for measuring the aviation kerosene liquid level (the freezing point temperature is lower than-55 ℃) on a passenger plane with low maneuverability, and the precision is higher. But still have limitations for some special applications. For example, vehicles with strong maneuverability and widely varying attitudes, the reflected wave reflection path will deviate from the defined measurement line because the liquid surface is not perpendicular to the measurement line, resulting in large measurement error and even failure.
3. The ultrasonic sensor is arranged at the bottom in the measuring cylinder, and a floater for tracking the liquid level is arranged in the measuring cylinder. The float geometry is cylindrical. The guide of the floater adopts a steel wire, an inner cylindrical surface or an outer cylindrical surface. The lower end surface of the cylindrical floater is used for reflecting ultrasonic waves during measurement. The normal line of the end face of the float of the structure can be always aligned with the end face of the ultrasonic conversion ring (14), namely, the measuring path through which the ultrasonic wave passes is not influenced by the posture of the container, the acceleration and the liquid fluctuation and is kept on a defined measuring line. But accuracy and stability as well as reliability are to be improved. The reason is that when the floater tracks the liquid level, the floater is influenced by the static friction force of the guide pair of the guide mechanism, and particularly under the conditions of large inclination and large acceleration, the tracking process can generate a clamping stagnation phenomenon, so that the error of a measuring result is large and even the floater fails.
Disclosure of Invention
The invention provides an anti-inclination and anti-fluctuation ultrasonic liquid level sensor and an application and treatment method thereof aiming at the defects of the existing liquid level sensor for ultrasonic measurement.
The specific implementation content of the invention is as follows:
the invention provides an anti-inclination and anti-fluctuation ultrasonic liquid level sensor, which is arranged in a liquid container and connected with a signal processing system, wherein the ultrasonic liquid level sensor comprises a waveguide tube which is vertically arranged in the liquid container, and the upper end and the lower end of the waveguide tube are respectively connected with the upper end and the lower end in the liquid container; the thickness of the tube wall of the waveguide tube is half of the transmission wavelength of the sound wave in the waveguide tube; a temperature sensor is arranged on the outer wall of the waveguide tube;
the liquid container is filled with the liquid to be measured, and a plurality of flow guide holes which enable the liquid to be measured to flow between the liquid container and the waveguide tube are circumferentially arranged on the waveguide tube;
the bottom of the waveguide tube is provided with a measuring piezoelectric sheet connected with a signal processing system, the measuring piezoelectric sheet is provided with a conversion ring, and a floating ball floating along with the liquid level surface of the liquid to be measured is arranged above the measuring piezoelectric sheet in the waveguide tube;
a calibration cylinder is arranged at the outer side of the bottom end of the waveguide tube in the liquid container, and a plurality of flow guide holes for enabling the liquid to be measured to flow between the liquid container and the calibration cylinder are circumferentially arranged on the calibration cylinder;
and a calibration piezoelectric sheet connected with the signal processing system and a calibration block matched with the calibration piezoelectric sheet are arranged in the calibration cylinder.
In order to better realize the invention, the invention further comprises a protective base and a sealing cover; the sealing cover is arranged at the top end of the waveguide tube and is hermetically connected with the top end of the interior of the liquid container;
the protection base is of a cylindrical structure with an opening at the upper end, the bottom end of the protection base is hermetically connected with the bottom end of the interior of the liquid container, and the bottom end of the waveguide tube is sleeved and fixed in the waveguide tube from the upper end of the protection base;
the inside bottom of protection base sets up the back sheet, measure the piezoelectric patch setting and just be located the top of back sheet at the bottom of waveguide tube.
In order to better realize the invention, further, the backing layer is a mixture of spherical tungsten powder and epoxy resin, and steel balls are uniformly doped in the mixture of spherical tungsten powder and epoxy resin; the diameter of the steel ball is between 0.3mm and 0.7 mm.
In order to better realize the invention, the invention further comprises a lateral silicone rubber ring and a bottom silicone rubber ring;
the side silicone rubber ring is arranged in the protective base and positioned at the outer side of the back lining layer;
the bottom silicon rubber ring is arranged in the protective base and positioned at the bottom of the back lining layer.
In order to better implement the invention, further, the waveguide comprises a matching layer, wherein the matching layer is arranged in the waveguide at the upper position of the piezoelectric measuring sheet;
defining the characteristic impedance of the piezoelectric sheet to be measured as Z1The characteristic impedance of the matching layer is Z2The characteristic impedance of the measured liquid is Z3The transmission coefficient of the sound intensity transmitted from the measurement piezoelectric sheet to the measured liquid is T, and the wavelength of the sound wave in the matching layer is lambda2The thickness of the matching layer is d1；
The characteristic impedance of the matching layer satisfies
Thickness of matching layer
Wherein n is a positive integer; the transmission coefficient T is 1, and the calculation formula of the transmission coefficient T is as follows:
where ω is the angular frequency of the ultrasonic wave, and C2 is the speed of sound of the ultrasonic wave in the matching layer.
In order to better implement the invention, the waveguide tube further comprises an anti-collision metal net, wherein the anti-collision metal net is arranged at the bottom of the waveguide tube and is positioned between the measuring piezoelectric sheet and the floating ball.
In order to better realize the invention, further, the floating ball is made of stainless steel 304 and is in a hollow spherical shape, the diameter is 35mm, the roundness error is +/-0.1 mm, the surface of the floating ball is polished by a mirror surface, and the thickness of the ball wall of the floating ball is 0.3 mm;
the waveguide tube is a carbon fiber composite circular tube, the length of the waveguide tube is 1000mm, the inner diameter of the waveguide tube is 36mm, the outer diameter of the waveguide tube is 38.5mm, 3 phi 4 diversion holes are uniformly distributed at the bottom end and the middle end of the waveguide tube in the circumferential direction, and polyurethane wave-absorbing materials with the thickness of 0.01mm are sprayed on the inner wall of the waveguide tube;
the calibration cylinder is made of carbon fiber composite materials, the cylinder length is 150mm, the inner diameter is 15mm, the outer diameter is 17mm, and 2 phi 3 diversion holes are uniformly distributed at the bottom end and the middle end of the calibration cylinder in the circumferential direction;
the protective base is made of aviation aluminum material;
the frequency of the measuring piezoelectric sheet and the calibration piezoelectric sheet is 1MHz, the diameter phi of the measuring piezoelectric sheet is 35mm, the diameter phi of the calibrating piezoelectric sheet is 15mm, and the piezoelectric coefficient is larger than 800 multiplied by 10-3C/N piezoelectric ceramics.
An application method of an anti-inclination and anti-fluctuation ultrasonic liquid level sensor is based on the anti-inclination and anti-fluctuation ultrasonic liquid level sensor, and is characterized by comprising the following steps:
firstly, an excitation pulse is sent to a calibration piezoelectric patch in a calibration cylinder through a signal processing system, so that the calibration piezoelectric patch is excited to emit ultrasonic vibration;
secondly, when the ultrasonic wave emitted by the calibration piezoelectric sheet is transmitted to the standard reflection block, a reflected wave is generated, and the ultrasonic wave crossing time t of the calibration piezoelectric sheet and the standard reflection block is obtained according to the ultrasonic wave principle0Fixed distance L between known calibration piezo-electric sheet and standard reflector block0On the basis, the real-time sound velocity V is obtained according to a velocity-time distance formula;
then, an excitation pulse is sent to the measurement piezoelectric patch in the waveguide tube through a signal processing system, so that the measurement piezoelectric patch is excited to emit ultrasonic vibration;
and then, when the ultrasonic wave emitted by the measuring piezoelectric plate is transmitted to the lower surface of the floating ball, a reflected wave reflected back to the measuring piezoelectric plate is generated, and finally, the liquid level L of the liquid to be measured is obtained according to a speed-time distance formula.
A signal processing method of an anti-inclination and anti-fluctuation ultrasonic liquid level sensor is used for carrying out ultrasonic calculation processing in the application method of the anti-inclination and anti-fluctuation ultrasonic liquid level sensor, and is characterized by comprising the following steps:
firstly, enveloping an echo by adopting full-wave detection;
then, the position Pmax of the maximum correlation coefficient P is obtained by adopting an autocorrelation algorithm, wherein the size of a correlation algorithm window of the autocorrelation algorithm is half of the envelope width, namely the half width of the Gaussian narrow pulse;
then, obtaining the slope Ki of the curve corresponding to the half envelope width in the echo, setting a slope comparison value, and judging the slope Ki after obtaining the position Pmax with the maximum correlation coefficient P: and when the slope Ki is larger than the set slope comparison value, judging the position Pmax as the echo position, otherwise, not judging the position as the echo position.
In order to better implement the invention, a high liquid level area and a low liquid level area are further set in the liquid container, a plurality of positions P (i) with close correlation coefficients and in an equal difference series exist in the low liquid level area, and the liquid level height is determined by adopting the time difference of the position P (i) and the position P (i-1) in the low liquid level area.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) compared with the traditional cylindrical steel wire floater, the spherical floater does not have clamping stagnation between guide rails, reduces friction, and can be compatible with various inclination angles and acceleration fluctuation;
(2) in order to enable the sound wave of the piston sound source to radiate into a medium with larger transmissivity, a matching layer technology is adopted at the piston sound source, in order to reduce the intensity of a reflected wave sound field, the sound wave is enabled to be transmitted out of the pipe wall at the pipe wall as far as possible and then to radiate outside the circular pipe, and the amplitude of part of sound wave in a high-order mode is reduced by adopting the circular pipe sound transmission window principle;
(3) the addition of the backing layer reduces the influence of bottom echo on excitation and the interference of bottom clutter on a measurement signal;
(4) and a matched calculation method is adopted to realize accurate measurement under the spherical floater.
Drawings
FIG. 1 is a schematic view of a sensor of the present invention installed in a liquid container;
FIG. 2 is a schematic diagram of a specific structure of a sensor;
FIG. 3 is a schematic view of a perpendicular incidence dielectric interface of a measurement piezoelectric patch, a matching layer and a measured liquid;
FIG. 4 is a schematic view of the interface of the liquid being measured and the waveguide;
FIG. 5 is a schematic view of a sound field of a round tube sound-transmitting window according to the present invention;
FIG. 6 is a schematic diagram of the acoustic field in the waveguide from the transmission of the ultrasonic waves to the return of the reflected waves according to the present invention;
wherein: 1. the liquid container, 2, waveguide tube, 3, protection base, 4, calibration cylinder, 5, calibration piezoelectric plate, 6, calibration reflection block, 7, measurement piezoelectric plate, 8, measured liquid, 9, liquid level, 10, floating ball, 11, sealing cover, 12, back lining layer, 13, matching layer, 14, conversion ring, 15, anti-collision metal net, 16, side silicone rubber ring, 17, bottom silicone rubber ring, 18, reference block, A, dominant wave, B, reference block reflection wave, C, high order wave.
Detailed Description
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and therefore should not be considered as a limitation to the scope of protection. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Example 1:
the embodiment provides an anti-inclination and anti-fluctuation ultrasonic liquid level sensor, which is installed in a liquid container 1 and connected with a signal processing system, as shown in fig. 1 and 2, the ultrasonic liquid level sensor comprises a waveguide tube 2 vertically installed in the liquid container 1, and the upper end and the lower end of the waveguide tube are respectively connected with the upper end and the lower end inside the liquid container 1; the thickness of the tube wall of the waveguide tube 2 is half of the transmission wavelength of the sound wave in the waveguide tube 2; a temperature sensor is arranged on the outer wall of the waveguide tube 2;
the liquid container 1 is filled with a measured liquid 8, and a plurality of guide holes for enabling the measured liquid 8 to flow between the liquid container 1 and the waveguide tube 2 are circumferentially arranged on the waveguide tube 2;
a measuring piezoelectric sheet 7 connected with a signal processing system is arranged at the bottom of the waveguide tube 2, a conversion ring 14 is arranged on the measuring piezoelectric sheet 7, and a floating ball 10 floating along with the liquid level surface 9 of the measured liquid 8 is arranged above the measuring piezoelectric sheet 7 in the waveguide tube 2;
a calibration cylinder 4 is arranged at the outer side of the bottom end of the waveguide tube 2 in the liquid container 1, and a plurality of flow guide holes for enabling the liquid 8 to be measured to flow between the liquid container 1 and the calibration cylinder 4 are circumferentially arranged on the calibration cylinder 4;
the calibration cylinder 4 is internally provided with a calibration piezoelectric patch 10 connected with a signal processing system and a calibration block matched with the calibration piezoelectric patch 10.
The working principle is as follows: firstly, an excitation pulse is sent to a calibration piezoelectric sheet 5 in a calibration cylinder 4 through a signal processing system, so that the calibration piezoelectric sheet 5 is excited to emit ultrasonic vibration;
secondly, when the ultrasonic wave emitted by the calibration piezoelectric sheet 5 is transmitted to the standard reflection block 6, a reflected wave is generated, and the ultrasonic wave crossing time t of the calibration piezoelectric sheet 5 and the standard reflection block 6 is obtained according to the ultrasonic wave principle0A fixed distance L between the known calibration piezo-electric strip 5 and the standard reflector block 60On the basis, the real-time sound velocity V is obtained according to a velocity-time distance formula;
then, an excitation pulse is sent to the measurement piezoelectric patch 7 in the waveguide 2 through a signal processing system, so that the measurement piezoelectric patch 7 is excited to emit ultrasonic vibration;
then, when the ultrasonic wave emitted by the measurement piezoelectric plate 7 is transmitted to the lower surface of the floating ball 10, a reflected wave reflected back to the measurement piezoelectric plate 7 is generated, and finally, the liquid level L of the measured liquid 8 is obtained according to a speed-time distance formula.
Example 2:
in this embodiment, on the basis of embodiment 1 above, in order to better implement the present invention, as shown in fig. 2, the protection base 3 and the sealing cover 11 are further included; the sealing cover 11 is arranged at the top end of the waveguide tube 2 and is hermetically connected with the top end inside the liquid container 1;
the protection base 3 is a cylindrical structure with an opening at the upper end, the bottom end of the protection base 3 is hermetically connected with the bottom end of the interior of the liquid container 1, and the bottom end of the waveguide tube 2 is sleeved and fixed in the waveguide tube 2 from the upper end of the protection base 3;
and a backing layer 12 is arranged at the bottom end inside the protective base 3, and the measuring piezoelectric sheet 7 is arranged at the bottom of the waveguide tube 2 and is positioned above the backing layer 12.
The backing layer 12 is a mixture of spherical tungsten powder and epoxy resin, and steel balls are uniformly doped in the mixture of the spherical tungsten powder and the epoxy resin; the diameter of the steel ball is between 0.3mm and 0.7 mm.
The working principle is as follows: the addition of the backing layer 12 may reduce the effects of ground echo on the excitation and ground clutter on the measurement signal.
Other parts of this embodiment are the same as those of embodiment 1, and thus are not described again.
Example 3:
in this embodiment, on the basis of the above embodiment 2, in order to better implement the present invention, as shown in fig. 2, the present invention further includes a side silicone rubber ring 16 and a bottom silicone rubber ring 17;
the lateral silicone rubber ring 16 is arranged in the protective base 3 and positioned at the outer side of the back lining layer 12;
the bottom silicone rubber ring 17 is disposed within the protective base 3 at the bottom of the backing layer 12.
The other parts of this embodiment are the same as those of embodiment 2, and thus are not described again.
Example 4:
in this embodiment, on the basis of any one of the above embodiments 1 to 3, in order to better implement the present invention, as further shown in fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5, a matching layer 13 is further included, where the matching layer 13 is disposed in the waveguide 2 at a position above the measurement piezoelectric plate 7;
the characteristic impedance of the piezoelectric sheet 7 is defined as Z1The characteristic impedance of the matching layer 13 is Z2The characteristic impedance of the measured liquid 8 is Z3The transmission coefficient of the sound intensity transmitted from the measurement piezoelectric sheet 7 to the measured liquid 8 is T, and the wavelength of the sound wave in the matching layer 13 is lambda2The thickness of the matching layer 13 is d1；
The characteristic impedance of the matching layer 13 satisfies
Thickness of the matching layer 13
Wherein n is a positive integer; the transmission coefficient T is 1, and the calculation formula of the transmission coefficient T is as follows:
where ω is the angular frequency of the ultrasonic wave, and C2 is the speed of sound of the ultrasonic wave in the matching layer.
The working principle is as follows: in order to enable sound waves emitted by a piston sound source, namely the measurement piezoelectric sheet 7 to radiate into a medium with high transmissivity, a matching layer technology is adopted at the position of the piston sound source, namely the measurement piezoelectric sheet 7, in order to reduce the intensity of a reflected wave sound field, the sound waves are enabled to be transmitted out of the tube wall of the waveguide tube 2 as far as possible to radiate to the outside of the waveguide tube 2, and the amplitude of part of sound waves in a high-order mode is reduced by adopting a circular tube sound transmission window principle.
As shown in FIG. 3, the characteristic impedance of the piezoelectric sheet 7 was measured as Z in consideration of the case where the interface with the medium was perpendicularly incident1The characteristic impedance of the matching layer 13 is Z2The thickness of the matching layer 13 is d1The characteristic impedance of the measured liquid 8 is Z3. The transmission coefficient of the sound intensity transmitted into the measured liquid 8 by the measurement piezoelectric sheet 7 is T, that is:
when the characteristic impedance of the matching layer 13 is satisfied
And thickness
Where is λ2Is the wavelength of the acoustic wave in the matching layer 13, N ∈ N), and the transmission coefficient T is 1. The matching layer technology is adopted to improve the energy coupling of the measurement piezoelectric sheet 7 into the measured liquid 8.
Similarly, as shown in FIG. 4, in the two-layer interface formed by the liquid 8 to be measured and the waveguide 2, the characteristic impedance of the waveguide 2 is Z4, and the wavelength of the acoustic wave in the waveguide 2 is λ4The thickness of the waveguide 2 is d2. When the thickness d of the waveguide 22In that
In the vicinity, the transmission coefficient of the acoustic wave radiated from the liquid 8 to be measured into the liquid medium through the waveguide is close to 1. At this time, the waveguide tube functions as an acoustic window. With the increase of the incident angle, especially when the incident angle is larger than the critical angle, total reflection occurs, therefore, a part of the sound wave scattered by the rigid floating ball is transmitted by the sound transmission window, and the influence of high-order mode waves is reduced.
As shown in fig. 5, the sound field schematic diagram of the round tube sound-transparent window is shown, the liquid medium is water, the rigid floating ball is a 304 stainless steel floating ball, the waveguide tube is a carbon fiber composite round tube, the thickness of the tube wall is half of the wavelength and is approximately equal to 1.25mm, the matching layer is made of polytetrafluoroethylene, and the thickness of the matching layer is quarter of the wavelength and is approximately equal to 1 mm. The ultrasonic liquid level sensor not only reduces the energy of partial high-order mode waves and improves the signal-to-noise ratio, but also greatly lightens the mass compared with the traditional metal circular tube sensor, and makes the ultrasonic liquid level sensor light.
Other parts of this embodiment are the same as any of embodiments 1 to 3, and thus are not described again.
Example 5:
in this embodiment, on the basis of any one of the above embodiments 1 to 4, in order to better implement the present invention, further, an anti-collision metal mesh 15 is further included, and the anti-collision metal mesh 15 is installed at the bottom of the waveguide 2 and is located between the measuring piezoelectric plate 7 and the floating ball 10.
The working principle is as follows: the floating ball 10 is prevented from colliding with the measuring piezoelectric plate 7 by arranging the anti-collision metal net 15.
Other parts of this embodiment are the same as any of embodiments 1 to 4, and thus are not described again.
Example 6:
in this embodiment, on the basis of any one of the above embodiments 1 to 5, in order to better implement the present invention, further, the floating ball 10 is made of stainless steel 304, and is in a hollow spherical shape, the diameter of the floating ball is 35mm, the roundness error is ± 0.1mm, the surface of the floating ball is mirror-polished, and the thickness of the spherical wall of the floating ball 10 is 0.3 mm;
the waveguide tube 2 is a carbon fiber composite circular tube, the length of the tube is 1000mm, the inner diameter is 36mm, the outer diameter is 38.5mm, 3 phi 4 diversion holes are uniformly distributed at the bottom end and the middle end of the waveguide tube 2 in the circumferential direction, and a polyurethane wave-absorbing material with the thickness of 0.01mm is sprayed on the inner wall of the waveguide tube 2;
the calibration cylinder 4 is made of carbon fiber composite materials, the cylinder length is 150mm, the inner diameter is 15mm, the outer diameter is 17mm, and 2 phi 3 diversion holes are uniformly distributed at the bottom end and the middle end of the calibration cylinder 4 in the circumferential direction;
the protective base 3 is made of an aviation aluminum material;
the measuring piezoelectric sheet 7 and the calibrating piezoelectric sheet 5 adopt the frequency of 1MHz, the diameter phi of 35mm and the diameter phi of 15mm, and the piezoelectric coefficient is larger than 800 multiplied by 10-3C/N piezoelectric ceramics.
Other parts of this embodiment are the same as any of embodiments 1 to 5, and thus are not described again.
Example 7:
in this embodiment, on the basis of any one of embodiments 1 to 6, taking the waveguide 2 with a height of 330mm as an example, as shown in fig. 6, fig. 6 is a schematic state flow chart of a sound field from the measurement piezoelectric plate 7 emitting ultrasonic waves to the ultrasonic waves reflected back by the floating ball 10 sequentially from left to right, it can be seen that an ultrasonic main wave a is emitted from the measurement piezoelectric plate 7, the reference block 18 is disposed in the waveguide 2, the ultrasonic main wave a is a reference block reflected wave B reflected back by the reference block 18, and the ultrasonic main wave a is reflected back to the measurement piezoelectric plate 7 after passing through the floating ball 10 and brings back part of the high-order wave C. The pressure gauge for distinguishing the total sound field pressure is on the right side of FIG. 6, wherein the color corresponds to the corresponding sound field pressure value in the sound field schematic diagram, because the color of the drawing is limited, the background of the waveguide 2 is green, and corresponds to the pressure gauge1×103Pa to 1X 103Pa, the colors of the ultrasonic main wave a, the reference block reflected wave B, and the higher order wave C in the waveguide 2 in different states are difficult to distinguish after being converted into black and white pictures, and therefore, the description will be made in a data format below the waveguide 2 in the corresponding state of fig. 6, and although the distinguished colors are not shown in fig. 6, fig. 6 is a test data screenshot, which does not substantially affect the technical solution described in the present application, and thus, the description will be given.
Other parts of this embodiment are the same as any of embodiments 1 to 6, and thus are not described again.
Example 8:
the embodiment provides an application method of an anti-inclination and anti-fluctuation ultrasonic liquid level sensor, which is based on the anti-inclination and anti-fluctuation ultrasonic liquid level sensor and is characterized by comprising the following steps:
firstly, an excitation pulse is sent to a calibration piezoelectric sheet 5 in a calibration cylinder 4 through a signal processing system, so that the calibration piezoelectric sheet 5 is excited to emit ultrasonic vibration;
secondly, when the ultrasonic wave emitted by the calibration piezoelectric sheet 5 is transmitted to the standard reflection block 6, a reflected wave is generated, and the ultrasonic wave crossing time t of the calibration piezoelectric sheet 5 and the standard reflection block 6 is obtained according to the ultrasonic wave principle0A fixed distance L between the known calibration piezo-electric strip 5 and the standard reflector block 60On the basis, the real-time sound velocity V is obtained according to a velocity-time distance formula;
then, an excitation pulse is sent to the measurement piezoelectric patch 7 in the waveguide 2 through a signal processing system, so that the measurement piezoelectric patch 7 is excited to emit ultrasonic vibration;
then, when the ultrasonic wave emitted by the measurement piezoelectric plate 7 is transmitted to the lower surface of the floating ball 10, a reflected wave reflected back to the measurement piezoelectric plate 7 is generated, and finally, the liquid level L of the measured liquid 8 is obtained according to a speed-time distance formula.
Example 9:
the embodiment provides a signal processing method of an anti-inclination and anti-fluctuation ultrasonic liquid level sensor, which is used for performing ultrasonic calculation processing in the application method of the anti-inclination and anti-fluctuation ultrasonic liquid level sensor, and is characterized by comprising the following steps of:
firstly, enveloping an echo by adopting full-wave detection;
then, the position Pmax of the maximum correlation coefficient P is obtained by adopting an autocorrelation algorithm, wherein the size of a correlation algorithm window of the autocorrelation algorithm is half of the envelope width, namely the half width of the Gaussian narrow pulse;
then, obtaining the slope Ki of the curve corresponding to the half envelope width in the echo, setting a slope comparison value, and judging the slope Ki after obtaining the position Pmax with the maximum correlation coefficient P: and when the slope Ki is larger than the set slope comparison value, judging the position Pmax as the echo position, otherwise, not judging the position as the echo position.
Example 10:
in this embodiment, in order to further realize the present invention in an improved manner on the basis of embodiment 9 described above, a high liquid level region and a low liquid level region are set in the liquid container 1, and in the low liquid level region, there are a plurality of positions P (i) having close correlation coefficients and in an arithmetic progression, and the liquid level height is determined in the low liquid level region by calculating the time difference between the positions P (i) and P (i-1).
Other parts of this embodiment are the same as those of embodiment 9, and thus are not described again.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (10)
1. An ultrasonic liquid level sensor resisting inclination and fluctuation is arranged in a liquid container (1) and is connected with a signal processing system, and is characterized in that the ultrasonic liquid level sensor comprises a waveguide tube (2) which is vertically arranged in the liquid container (1) and the upper end and the lower end of the waveguide tube are respectively connected with the upper end and the lower end in the liquid container (1); the thickness of the tube wall of the waveguide tube (2) is half of the transmission wavelength of the sound wave in the waveguide tube (2); a temperature sensor is arranged on the outer wall of the waveguide tube (2);
the liquid container (1) is filled with a measured liquid (8), and a plurality of flow guide holes for enabling the measured liquid (8) to flow between the liquid container (1) and the waveguide tube (2) are circumferentially arranged on the waveguide tube (2);
a measuring piezoelectric sheet (7) connected with a signal processing system is arranged at the bottom of the waveguide tube (2), a conversion ring (14) used for packaging the measuring piezoelectric sheet (7) is arranged on the measuring piezoelectric sheet (7), and a floating ball (10) floating along with the liquid level surface (9) of the measured liquid (8) is arranged above the measuring piezoelectric sheet (7) in the waveguide tube (2);
a calibration cylinder (4) is arranged at the outer side of the bottom end of the waveguide tube (2) in the liquid container (1), and a plurality of flow guide holes for enabling the liquid to be measured (8) to flow between the liquid container (1) and the calibration cylinder (4) are circumferentially arranged on the calibration cylinder (4);
the calibration cylinder (4) is internally provided with a calibration piezoelectric sheet (10) connected with a signal processing system and a calibration block matched with the calibration piezoelectric sheet (10).
2. An ultrasonic level sensor resistant to tilting and waves as claimed in claim 1, characterized by further comprising a protective base (3) and a flap (11); the sealing cover (11) is arranged at the top end of the waveguide tube (2) and is hermetically connected with the top end of the interior of the liquid container (1);
the protection base (3) is of a cylindrical structure with an opening at the upper end, the bottom end of the protection base (3) is hermetically connected with the bottom end of the interior of the liquid container (1), and the bottom end of the waveguide tube (2) is sleeved and fixed in the waveguide tube (2) from the upper end of the protection base (3);
and a backing layer (12) is arranged at the bottom end inside the protective base (3), and the measuring piezoelectric sheet (7) is arranged at the bottom of the waveguide tube (2) and is positioned above the backing layer (12).
3. The ultrasonic level sensor of claim 2, wherein the backing layer (12) is a mixture of spherical tungsten powder and epoxy resin, and the mixture of spherical tungsten powder and epoxy resin is also uniformly doped with steel balls; the diameter of the steel ball is between 0.3mm and 0.7 mm.
4. An ultrasonic level sensor resistant to tilting and waves as claimed in claim 3, characterized by further comprising lateral silicone rubber rings (16) and bottom silicone rubber rings (17);
the side silicone rubber ring (16) is arranged in the protective base (3) and is positioned at the outer side of the back lining layer (12);
the bottom silicon rubber ring (17) is arranged in the protective base (3) and is positioned at the bottom of the back lining layer (12).
5. An ultrasonic level sensor resistant to inclination and undulation according to claim 1, characterized by further comprising a matching layer (13), said matching layer (13) being arranged inside said waveguide (2) at a position above the measurement piezoelectric patch (7);
defining the characteristic impedance of the piezoelectric sheet (7) to be measured as Z1The characteristic impedance of the matching layer (13) is Z2The characteristic impedance of the measured liquid (8) is Z3The transmission coefficient of the sound intensity transmitted from the measurement piezoelectric sheet (7) to the measured liquid (8) is T, and the wavelength of the sound wave in the matching layer (13) is lambda2The thickness of the matching layer (13) is d1；
The characteristic impedance of the matching layer (13) satisfies
Thickness of the matching layer (13)
Wherein n is a positive integer; the transmission coefficient T is 1, and the calculation formula of the transmission coefficient T is as follows:
where ω is the angular frequency of the ultrasonic wave, and C2 is the speed of sound of the ultrasonic wave in the matching layer.
6. An ultrasonic level sensor resistant to inclination and undulation according to claim 1, characterized in that it further comprises a crash wire (15), said crash wire (15) being mounted at the bottom of the waveguide (2) and being located between the piezoelectric measuring patch (7) and the float ball (10).
7. The ultrasonic liquid level sensor resisting inclination and fluctuation according to any one of claims 1 to 6, wherein the floating ball (10) is made of stainless steel 304, is in a hollow spherical shape, has a diameter of 35mm, a roundness error of +/-0.1 mm, is mirror-polished on the surface, and has a ball wall thickness of 0.3 mm;
the waveguide tube (2) is a carbon fiber composite circular tube, the length of the tube is 1000mm, the inner diameter of the tube is 36mm, the outer diameter of the tube is 38.5mm, 3 phi 4 diversion holes are uniformly distributed at the bottom end and the middle end of the waveguide tube (2) in the circumferential direction, and a polyurethane wave-absorbing material with the thickness of 0.01mm is sprayed on the inner wall of the waveguide tube (2);
the calibration cylinder (4) is made of carbon fiber composite materials, the cylinder length is 150mm, the inner diameter is 15mm, the outer diameter is 17mm, and 2 phi 3 diversion holes are uniformly distributed at the bottom end and the middle end of the calibration cylinder (4) in the circumferential direction;
the protective base (3) is made of an aviation aluminum material;
the measuring piezoelectric sheet (7) and the calibration piezoelectric sheet (5) adopt the frequency of 1MHz, the diameter phi of 35mm and the diameter phi of 15mm, and the piezoelectric coefficient is more than 800 multiplied by 10-3C/N piezoelectric ceramics.
8. A method of use of a tilt and wave resistant ultrasonic level sensor according to claim 1, comprising the steps of:
firstly, an excitation pulse is sent to a calibration piezoelectric sheet (5) in a calibration cylinder (4) through a signal processing system, so that the calibration piezoelectric sheet (5) is excited to emit ultrasonic vibration;
secondly, when the ultrasonic wave emitted by the calibration piezoelectric sheet (5) is transmitted to the standard reflection block (6), a reflected wave is generated, and the ultrasonic wave crossing time t of the calibration piezoelectric sheet (5) and the standard reflection block (6) is obtained according to the ultrasonic principle0Fixation between a known calibration piezo-electric strip (5) and a standard reflector block (6)Distance L0On the basis, the real-time sound velocity V is obtained according to a velocity-time distance formula; then, an excitation pulse is sent to the measurement piezoelectric sheet (7) in the waveguide tube (2) through a signal processing system, so that the measurement piezoelectric sheet (7) is excited to emit ultrasonic vibration;
then, when the ultrasonic wave emitted by the measuring piezoelectric sheet (7) is transmitted to the lower surface of the floating ball (10), a reflected wave reflected back to the measuring piezoelectric sheet (7) is generated, and finally, the liquid level L of the measured liquid (8) is obtained according to a speed-time distance formula.
9. A method of processing signals of an anti-tilt and anti-wave ultrasonic level sensor for performing ultrasonic wave calculation processing in a method of applying an anti-tilt and anti-wave ultrasonic level sensor according to claim 8, comprising the steps of:
firstly, enveloping an echo by adopting full-wave detection;
then, the position Pmax of the maximum correlation coefficient P is obtained by adopting an autocorrelation algorithm, wherein the size of a correlation algorithm window of the autocorrelation algorithm is half of the envelope width, namely the half width of the Gaussian narrow pulse;
then, obtaining the slope Ki of the curve corresponding to the half envelope width in the echo, setting a slope comparison value, and judging the slope Ki after obtaining the position Pmax with the maximum correlation coefficient P: and when the slope Ki is larger than the set slope comparison value, judging the position Pmax as the echo position, otherwise, not judging the position as the echo position.
10. The method of claim 9, wherein a high level region and a low level region are set in the liquid container (1), and for the low level region, there are a plurality of positions P (i) with close correlation coefficients and in an arithmetic series, and in the low level region, the liquid level height is determined by taking the time difference between the positions P (i) and P (i-1); the position P (i) and the position P (i-1) are adjacent position points.
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