CN114046871B - A portable ultrasonic sound pressure measurement device based on the principle of acoustic capillary effect - Google Patents
A portable ultrasonic sound pressure measurement device based on the principle of acoustic capillary effect Download PDFInfo
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- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
- G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
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Abstract
本发明涉及一种基于声致毛细效应原理的便携式超声波声压测量装置，包括探测部和主体部，探测部包括外套管和毛细管，毛细管设在外套管内，毛细管与外套管的内腔连通，装有不可压缩且已排除气泡的液体；主体部前端设有毛细管插孔，毛细管的底端伸入到主体部的毛细管插孔内，在毛细管插孔的底端设有压电薄膜；主体部内设有单片机。本发明通过超声波引起的毛细管口处的泵压，能够测得连续的超声波功率实时变化值，也可直接通过单片机进行数据分析获得该段时间内的超声波功率最大值、最小值以及平均值，在医疗领域和声化学反应领域有非常重要的作用。
The present invention relates to a portable ultrasonic sound pressure measuring device based on the principle of acoustic capillary effect, comprising a detection part and a main body, wherein the detection part comprises an outer sleeve and a capillary, the capillary is arranged in the outer sleeve, the capillary is connected with the inner cavity of the outer sleeve, and is filled with incompressible liquid from which bubbles have been eliminated; a capillary jack is arranged at the front end of the main body, the bottom end of the capillary extends into the capillary jack of the main body, a piezoelectric film is arranged at the bottom end of the capillary jack; and a single chip microcomputer is arranged in the main body. The present invention can measure the continuous real-time change value of ultrasonic power through the pump pressure at the capillary mouth caused by ultrasonic waves, and can also directly perform data analysis through the single chip microcomputer to obtain the maximum value, minimum value and average value of ultrasonic power within the period of time, which plays a very important role in the medical field and the field of sonochemical reaction.
Description
Technical Field
The present invention relates to an ultrasonic sound pressure measuring device, and more particularly, to a device for detecting ultrasonic power, i.e., sound pressure, designed based on the principle of acoustic capillary effect.
Background
At present, the application of ultrasonic waves in various fields is more and more widespread, and the ultrasonic power is too high, which is a main reason for the harm to human bodies, and the detection of whether the ultrasonic power is within a safety threshold value is of great significance. Meanwhile, the sonochemical reactor is widely applied, but ultrasonic power is inevitably dissipated along with time in a complex sonochemical environment, and detection of whether the ultrasonic power is stabilized at an expected output value is also significant for improving experimental accuracy. However, the conventional ultrasonic power measuring method, such as acoustic-optical effect acoustic intensity measurement, is too complex and bulky in equipment, and requires a computer to process the diffraction image by using a complex algorithm, so that a user needs to know rich image processing and writing capability of relevant codes of the computer, and the method has the advantages of high use threshold, difficulty in popularization and high uncertainty. In addition, the hydrophone of the common measuring instrument is difficult to be smaller than the wavelength of sound waves, so that sound field distortion is caused, the measurement accuracy is inevitably affected, and the hydrophone can only be used in water. Therefore, there is a need for a device for detecting ultrasonic power, i.e., sound pressure, that is small in size, high in sensitivity, and simple and easy to operate in a measurement method.
Disclosure of Invention
In order to solve the technical problems, the invention provides a portable ultrasonic sound pressure measuring device based on the principle of sound-induced capillary effect, which comprises a detection part and a main body part, wherein the detection part is arranged at the front end of the main body part, the detection part comprises an outer sleeve and a capillary, the bottom end of the outer sleeve is fixedly connected with the main body part, the capillary is arranged in the outer sleeve, the capillary is communicated with the inner cavity of the outer sleeve and filled with incompressible liquid which has eliminated bubbles, the front end of the main body part is provided with a capillary jack, the bottom end of the capillary extends into the capillary jack of the main body part, and the bottom end of the capillary jack is provided with a piezoelectric film;
The main body part is also internally provided with a power supply which is connected with the singlechip and provides electric energy, and the power supply comprises a battery and a voltage stabilizing circuit.
The top end of the outer sleeve is provided with a soft membrane surface.
The outer sleeve is internally provided with a limit groove, and the capillary tube is fixed in the limit groove.
Selecting a proper angle, extending the detection part into an ultrasonic field to be detected, converting external force received by the PVDF piezoelectric film when liquid enters and exits the capillary channel into a voltage signal, amplifying the weak voltage signal in the singlechip, converting high-impedance output into low-impedance output, filtering by using moving average filtering, performing analog-to-digital conversion by the singlechip, connecting an electric signal to a pin of an ADC channel which can be multiplexed by the singlechip, setting a sampling period, setting the conversion resolution to 16 bits, starting continuous conversion, converting the converted digital signal into a digital signal, obtaining a number x, and calculating the obtained number:
Wherein V 1 is the real voltage value at this time, and V ref is the reference voltage;
and then the sensitivity characteristic of the piezoelectric film is combined to calculate the pressure applied at the moment, and the area is removed to obtain the pressure to be measured The formula is introduced:
Wherein ρ is the fluid density, a is the kinetic energy correction coefficient, u 1 is the instantaneous flow rate at the capillary orifice, α is the expansion coefficient, α >1, A 1 is the capillary inner diameter area, A 2 is the capillary outer diameter area, Z 1 is the height at the capillary orifice, Z 2 is the height at the piezoelectric film, g is the gravitational acceleration, σ is the water tension coefficient, θ is the contact angle, r is the capillary inner diameter, P Air flow is the pressure caused by the floating of bubbles generated by the ultrasonic cavitation effect, Is the head loss in the pipeline;
The instantaneous flow velocity u 1 at the orifice of the capillary tube is obtained by the formula, the average vibration flow velocity u of the fluid at the orifice of the tube in one period can be calculated, and then the average vibration flow velocity u is substituted into the formula:
P=ρcu
the sound pressure value P here is calculated, where c is the propagation velocity of the sound.
The invention has the beneficial effects that:
The detection device provided by the invention is convenient to operate, the cost is low because the main analysis process depends on the singlechip, compared with the mechanical vibration signal of water converted by a commonly used hydrophone through a piezoelectric transducer, the detection device can be free from the influence of ultrasonic field distortion, the original sound field can not be changed, the measurement is more accurate, and meanwhile, the detection device can be used in most environments, is not limited in water or air, and only needs to place a detection part in the sound field environment to be measured. The continuous ultrasonic power real-time change value can be measured through the pump pressure at the capillary orifice caused by ultrasonic waves, and the maximum value, the minimum value and the average value of the ultrasonic power in the period of time can be obtained through data analysis by a singlechip, and the values can be directly displayed on a display screen of the device. The device has very important effect in the medical field and the sonochemistry reaction field, can monitor whether medical ultrasonic power exceeds the threshold value harmful to human body in real time, and can also guarantee to keep ideal stable ultrasonic power in complex sonochemistry reactor environment.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the present invention;
FIG. 2 is a schematic diagram of the internal structure of the present invention;
FIG. 3 is a schematic view of a cylindrical fluid element structure;
FIG. 4 is a schematic cross-sectional view of a nozzle.
1. A detection unit; 2, a main body part, 3, an outer sleeve, 4, a capillary tube, 5, a piezoelectric film, 6, a singlechip, 7, a key, 8, a display screen, 9, a power supply, 10, a soft film surface, 11 and a limit groove.
Detailed Description
The invention provides a portable ultrasonic sound pressure measuring device based on an acoustic capillary effect principle, which is shown in figures 1 and 2, and comprises a detecting part 1 and a main body part 2, wherein the detecting part 1 is arranged at the front end of the main body part 2, the detecting part 1 comprises an outer sleeve 3 and a capillary 4, the bottom end of the outer sleeve 3 is fixedly connected with the main body part 2, the capillary 4 is arranged in the outer sleeve 3, the capillary 4 is communicated with an inner cavity of the outer sleeve 3 and filled with incompressible liquid with bubbles removed, a capillary jack is arranged at the front end of the main body part 2, the bottom end of the capillary 4 extends into the capillary jack of the main body part, a PVDF piezoelectric film 5 is arranged at the bottom end of the capillary jack, a singlechip 6 is arranged in the main body part 2, the model 6STM32F103C8T6 singlechip is arranged on the surface of the main body part 2, and the singlechip is respectively connected with the PVDF piezoelectric film 5, the button 7 and the oled display 8.
The key 7 comprises five function keys and a switch key, wherein the five function keys are respectively a start/stop count key, a zero setting key, a maximum value key, a minimum value key and an average value key.
The main body part 2 is also provided with a power supply 9, the power supply 9 is connected with the singlechip 6 and provides electric energy, and the power supply 9 comprises a battery and a voltage stabilizing circuit.
The top end of the outer sleeve 3 is provided with a soft membrane surface 10 for providing a liquid vibration tolerance space.
Limiting grooves 11 are formed in the outer sleeve 3 at intervals 40-70 mm away from the bottom of the tube, and the capillary tubes 4 are fixed in the limiting grooves 11 to prevent the capillary tubes 4 from moving.
The invention is based on the phenomenon that the pumping pressure is generated by the loss energy difference of the fluid at the opening of the capillary tube 4 in and out of the pipeline due to the sound induced capillary effect, namely the ultrasonic wave causes the fluid to be swabbed. When the ultrasonic wave propagates in the fluid, the periodic vibration of the fluid in time and space can be caused, so that the fluid at the pipe orifice can enter and exit the pipeline at high frequency. It is known from fluid mechanics that when water flows into a pipe which is suddenly narrowed and a pipe which is suddenly narrowed, local resistance is different, energy loss is different, and the difference between the local resistance of the pipe which flows into the pipe and the energy loss generates pumping pressure of an ultrasonic pump.
Ultrasonic pump principle:
The fluid inside and outside the capillary 4 is analyzed under the cylindrical coordinate system, and the fluid is differentiated into cylindrical microelements, as shown in fig. 3 and 4.
The Bernoulli equation analysis is carried out on the fluid at the orifice of the capillary tube 4 to obtain the relation between the instantaneous section flow rate and the generated pressure difference between the 1-1 section and the 2-2 section:
Wherein, P 1 is the pressure at the 1-1 section, P 2 is the pressure at the 2-2 section, u 1 is the instantaneous flow rate of the fluid at the 1-1 section, i.e. the pipe orifice, u 2 is the instantaneous flow rate of the fluid at the 2-2 section, i.e. the outside of the pipe, ρ is the fluid density, g is the gravitational acceleration, a is the kinetic energy correction coefficient, In order to be a local resistance force,Ζ is the local drag coefficient;
Look-up table can be obtained, entering the capillary 4 orifice, ζ=0.5 (1-a 1/A2) denoted ζ Into (I) , exiting the capillary orifice, ζ= (1-a 1/A2)2 denoted ζ Out of ;
Wherein, A 1 is the inner diameter area of the capillary 4, and A 2 is the outer diameter area of the capillary 4;
In consideration of the situation that water overflows when impacting the orifice of the capillary tube 4, the research range needs to be expanded, the research range is expanded from the outer diameter R of the capillary tube 4 to R ', the expanded area is A ' 2, and the expansion coefficient alpha is introduced, the area of the part of water after impacting the capillary tube is reduced (only water is originally used, after impacting the orifice of the capillary tube, a part of the area is the capillary wall and a part of the area is water), and the area of the reduced water is A ' 1, so that the formula is as follows:
wherein, alpha is measured by experiments, when the ratio of the inner diameter to the outer diameter is 1:3, alpha is about 1.2, A '1 is the reduced area after the study object is enlarged, and A' 2 is the cylindrical area after the study object is enlarged;
Introducing a continuity equation:
A1V1＝A2V2 (3)
and (2) and (3) are combined to obtain the following components:
where Δp Into (I) is the pressure entering capillary 4 and Δp Out of is the pressure exiting capillary 4;
under high frequency vibration, macroscopic appearance is the mean pressure, i.e.:
substituting (4) (5) into (6) the average pressure of the fluid available is:
analysis of the fluid flowing within the channel, introducing the bernoulli total flow equation:
Here, P Air flow is the pressure caused by the rising of bubbles generated by the ultrasonic cavitation effect, Z 1 is the height at the orifice of the capillary, Z 2 is the height at the piezoelectric film, Z Wool (fur) is the height of the liquid column due to capillary action, Is the head loss in the pipeline;
Wherein sigma is a water tension coefficient, theta is a contact angle, and r is the inner diameter of the capillary;
The (7), (8) and (9) are simultaneously available:
By measuring pressure The instantaneous flow velocity u 1 at the capillary orifice can be obtained, the average vibration flow velocity u of the fluid at the inner orifice in one period can be calculated, and the average vibration flow velocity u is substituted into the formula:
P=ρcu (11)
where ρ is the fluid density and c is the propagation velocity of sound, where the sound pressure value P can be calculated.
Because the cavitation effect of ultrasonic wave produces unstable bubble pressure, the invention adopts the internal liquid environment to ensure the relative stability of the bubble pressure, and the bubble pressure is determined by pressure measurementValue:
Because of the same length of capillary channel, the resistance along the way is the same, so the pressure of the measuring liquid entering and exiting the capillary channel is replaced by the pressure at the bottom of the measuring tube, and the pressure measurement is performed by using the PVDF piezoelectric film 5.
The PVDF piezoelectric film 5 converts the external force to voltage, has high sensitivity and high response speed, can measure tiny pressure change, but has high impedance and small energy, so that a pre-amplifier with high input impedance is needed to be connected to amplify weak signals and convert high impedance output into low impedance output, and the signals are filtered due to excessive noise after being converted into electric signals with reaction pressure, and the signals are filtered by moving average filtering.
After filtering, the singlechip 6 carries out analog-to-digital conversion, the electric signal is connected to the pins of the ADC channel which can be multiplexed by the singlechip 6, the sampling period is set, the conversion resolution is set to 16 bits, and continuous conversion is started. After being converted into a digital signal, the obtained number is x, and the obtained number is calculated:
Wherein V 1 is the real voltage value at this time, and V ref is the reference voltage;
the pressure applied at the moment can be calculated by combining the sensitivity characteristic of the piezoelectric film 5 at the moment, and the area is removed to obtain the pressure to be measured
The device switch is turned on, a proper angle is selected, the detection part 1 stretches into an ultrasonic field to be detected, a zeroing button is pressed, the inclination angle of the device is kept from being changed greatly as much as possible after zeroing, after the start/stop counting button is pressed, a pressure value can be displayed on the oled display screen 8 in real time, the stop counting button is pressed again, the counting can be stopped, the display number on the oled display screen 8 is not updated any more, the pressure value between the two keys is stored in an array, the maximum value and the minimum value can be obtained by comparison after all values in the array are traversed, and all values in the array can be averaged, and the maximum value, the minimum value and the average value of the ultrasonic pressure in the period can be displayed by pressing the maximum value button, the minimum value button and the average value button.
Claims (4)
1. A portable ultrasonic sound pressure measuring device based on an acoustic capillary effect principle is characterized by comprising a detection part and a main body part, wherein the detection part is arranged at the front end of the main body part and comprises an outer sleeve and a capillary, the bottom end of the outer sleeve is fixedly connected with the main body part, the capillary is arranged in the outer sleeve and is communicated with the inner cavity of the outer sleeve and filled with incompressible liquid which is removed from bubbles, the top end of the outer sleeve is provided with a soft film surface, the front end of the main body part is provided with a capillary jack, the bottom end of the capillary extends into the capillary jack of the main body part, the bottom end of the capillary jack is provided with a piezoelectric film, the main body part is internally provided with a singlechip, and the surface of the main body part is provided with keys and a display screen which are respectively connected with the piezoelectric film, the keys and the display screen.
2. The portable ultrasonic sound pressure measuring device based on the principle of the sound induced capillary effect according to claim 1 is characterized in that a power supply is further arranged in the main body part and connected with the singlechip to supply electric energy, and the power supply comprises a battery and a voltage stabilizing circuit.
3. The portable ultrasonic sound pressure measuring device based on the principle of sound-induced capillary effect according to claim 1, wherein the outer sleeve is internally provided with a limit groove, and the capillary tube is fixed in the limit groove.
4. The portable ultrasonic sound pressure measuring device based on the principle of the acoustic capillary effect according to claim 1 is characterized in that a proper angle is selected, a detection part stretches into an ultrasonic field to be measured, an external force applied by a piezoelectric film when liquid enters and exits a capillary channel is converted into a voltage signal, the weak voltage signal is amplified in a singlechip, high-impedance output is converted into low-impedance output, filtering is carried out by moving average filtering, analog-digital conversion is carried out by the singlechip, the conversion resolution is set to 16 bits, continuous conversion is started, the obtained number is x after the conversion is carried out, and the obtained number is calculated:
Wherein V 1 is the real voltage value at this time, and V ref is the reference voltage;
and then the sensitivity characteristic of the piezoelectric film is combined to calculate the pressure applied at the moment, and the area is removed to obtain the pressure to be measured Carrying out a formula;
Wherein ρ is the fluid density, a is the kinetic energy correction coefficient, u 1 is the instantaneous flow rate at the capillary orifice, α is the expansion coefficient, α >1, A 1 is the capillary inner diameter area, A 2 is the capillary outer diameter area, Z 1 is the height at the capillary orifice, Z 2 is the height at the piezoelectric film, g is the gravitational acceleration, σ is the water tension coefficient, θ is the contact angle, r is the capillary inner diameter, P Air flow is the pressure caused by the floating of bubbles generated by the ultrasonic cavitation effect, Is the head loss in the pipeline;
The instantaneous flow velocity u 1 at the orifice of the capillary tube is obtained by the formula, the average vibration flow velocity u of the fluid at the orifice of the inner tube in one period is calculated, and then the average vibration flow velocity u is substituted into the formula:
P=ρcu
the sound pressure value P here is calculated, where c is the propagation velocity of the sound.
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| CN216410394U (en) * | 2021-11-12 | 2022-04-29 | 吉林大学 | A portable ultrasonic sound pressure measurement device based on the principle of sonocapillary effect |
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| DE69727422T2 (en) * | 1996-05-31 | 2004-07-01 | Packard Instrument Co., Inc., Downers Grove | Device for handling microfluidic quantities |
| DE102005007870B4 (en) * | 2005-02-21 | 2007-12-06 | E.G.O. Elektro-Gerätebau GmbH | Method and device for measuring the surface tension of liquids |
| FR2908329B1 (en) * | 2006-11-14 | 2011-01-07 | Telemaq | DEVICE AND METHOD FOR ULTRASOUND FLUID DELIVERY |
| SG148060A1 (en) * | 2007-05-25 | 2008-12-31 | Sony Corp | Method and system for evaluating acoustic directivity |
| CN102094784B (en) * | 2010-12-28 | 2012-11-21 | 哈尔滨工业大学 | Millimeter-sized honeycomb capillary ultrasonic micro-pump |
| CN110044467B (en) * | 2019-05-15 | 2021-09-28 | 重庆大学 | Optical fiber Fabry-Perot hydrophone radial coupling system for measuring sound field of spherical focusing sound collector |
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