Passive and wireless-based bimodal ultrasonic thickness measuring system
Through the passive wireless dual-mode ultrasonic thickness measurement system, using the dual-wave method processing of passive wireless ultrasonic sensors and dual-mode probes, the safety risks and measurement accuracy issues of manual thickness measurement in the petrochemical field are solved, and efficient and accurate thickness measurement is achieved.
Patent Information
- Application Number
- CN202511003614.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-09-09
AI Technical Summary
In the field of petrochemical industry, existing technologies such as manual ultrasonic thickness measurement have problems such as high safety risks, low measurement efficiency and inaccurate measurement accuracy. In particular, it is difficult to achieve efficient and accurate thickness measurement in high-temperature pipelines and high-altitude locations.
A passive wireless dual-mode ultrasonic thickness measurement system is used, which uses a passive wireless ultrasonic sensor and a dual-mode ultrasonic probe, combined with longitudinal and shear wave piezoelectric sheets, and processes the echo signal through the dual-wave method to achieve thickness measurement of the measured object, reduce power supply costs and improve measurement accuracy.
It reduces power input costs, reduces safety risks, and improves the accuracy of thickness measurement. In particular, it can accurately measure thickness under temperature fluctuations, solving the measurement error problem in traditional methods.
Smart Images
Figure CN120609307A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of thickness measurement, and in particular to a dual-mode ultrasonic thickness measurement system based on passive wireless. Background Art
[0002] In the fields of petrochemicals and other fields, timely understanding of the corrosion conditions of the inner walls of various pipelines is an important means to guide the adjustment of production processes and control production safety. For example, the petrochemical industry requires that the annual corrosion rate of pipelines does not exceed 0.076mm / year, so it is necessary to measure the wall thickness of the pipeline in a timely manner to determine whether the pipeline corrosion rate exceeds the standard. The best way is to use online corrosion monitoring methods, but petrochemical plants need to monitor a lot of points, and online monitoring methods are generally expensive. It is difficult for companies to bear the cost of installing corrosion monitoring systems on a large scale. The current method is generally: staff carry ultrasonic detectors and manually measure the thickness at the points that need to be tested. However, the disadvantages of manual thickness measurement are: 1. Petrochemical plants have a large number of pipelines located at high altitudes, and personnel need to frequently perform high-altitude operations, which poses high safety risks; 2. A large number of pipelines in petrochemical plants are high-temperature pipelines. The production of petrochemical products requires stable pipeline temperatures. Therefore, high-temperature pipelines are often wrapped with insulation layers. When performing manual ultrasonic thickness measurement, the insulation layer at the point to be measured needs to be removed and then restored after the measurement is completed. This process is very cumbersome and the measurement efficiency is low. 3. See Figure 1 During ultrasonic thickness measurement, the ultrasonic probe should be perpendicular to the normal of the pipe being measured, meaning the ultrasonic wave should propagate towards the pipe's center. However, due to differences in operator experience and habits, this can be difficult to ensure during actual ultrasonic thickness measurement, leading to significant errors.
[0003] Also, see Figure 2 The principle of ultrasonic thickness measurement is based on the flight time of the ultrasonic wave in the test piece and the sound velocity of the test piece material at the current temperature. , and use the following thickness calculation formula to get the thickness : , From the above thickness calculation formula, we can know that the premise of accurately obtaining the wall thickness is to obtain the ultrasonic flight time at the same time. The propagation speed of ultrasound in the medium. The propagation speed of ultrasound in a certain material is related to the temperature of the material, so it is crucial to obtain the temperature of the material being measured. In addition, since the temperature of the material being measured fluctuates within a certain range during actual operation, it is difficult to ensure measurement accuracy by relying on the material being measured and the propagation speed at different temperatures to measure thickness. Summary of the Invention
[0004] The purpose of the present invention is to provide a passive wireless dual-mode ultrasonic thickness measurement system, which can not only use a passive wireless ultrasonic sensor to measure the thickness of the test piece, thereby reducing the power supply cost, but also use a dual-wave method to process the echo signal. Even if the test piece is subject to temperature fluctuations during measurement, the thickness of the test piece can be accurately measured, thereby improving the measurement accuracy during thickness measurement.
[0005] The present invention solves the technical problem and adopts the following technical solution: Passive wireless dual-mode ultrasonic thickness measurement system, including: A passive wireless ultrasonic sensor is fixedly mounted on the device under test. The probe of the passive wireless ultrasonic sensor is a dual-mode ultrasonic probe. The dual-mode ultrasonic probe includes a longitudinal wave piezoelectric sheet and a transverse wave piezoelectric sheet. After receiving an excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test, ... An excitation unit, configured to send a periodic excitation signal to the passive wireless ultrasonic sensor; The signal receiving and processing unit is used to receive the echo signal, perform demodulation and dual-wave method processing, and obtain the thickness of the measured object.
[0006] As a further optimization, when the passive wireless ultrasonic sensor is fixedly mounted on the measured object, the probe of the passive wireless ultrasonic sensor is perpendicular to the normal line of the measured object.
[0007] As a further optimization, the excitation unit includes an ultrasonic excitation source, an oscillator, a frequency divider, a first mixer, a first power amplifier, a second amplifier, a first antenna group, a second antenna group and a third mixer; The ultrasonic excitation source is used to generate a frequency of The ultrasonic excitation signal of multiple cycles is input to the first mixer, and then stops working; The oscillator is always in the transmitting state, and is used to generate a frequency of The high frequency carrier signal is input to the frequency divider; The frequency divider is used to generate frequencies The first signal is input to the first mixer, and after being mixed with the ultrasonic excitation signal in the first mixer, a frequency of The mixed signal is amplified by the first power amplifier and then sent to the third mixer through the first antenna group, and the second signal is amplified by the second power amplifier and then sent to the third mixer through the second antenna group; The third mixer is used to mix the two signals sent by the first antenna group and the second antenna group, and input a frequency of several cycles to the dual-mode ultrasound probe. Ultrasonic excitation signal.
[0008] As a further optimization, when the dual-mode ultrasound probe receives a periodic frequency of After receiving the ultrasonic excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test; When the ultrasonic shear wave and the ultrasonic longitudinal wave are respectively transmitted in the test piece of the same material and the same temperature, the dual-mode ultrasonic probe senses an echo signal containing the propagation time of the ultrasonic longitudinal wave in the test piece and the propagation time of the ultrasonic shear wave in the test piece.
[0009] As a further optimization, the frequency of the echo signal is The echo signal is input to the third mixer, and the echo signal is mixed with the second signal amplified by the second power amplifier and sent through the second antenna group by the third mixer to obtain a frequency of The modulated echo signal is sent to the signal receiving and processing unit via the first antenna group.
[0010] As a further optimization, the signal receiving and processing unit includes a second mixer and a processor; The second mixer is used to receive the modulated echo signal sent by the first antenna group and the third signal generated by the frequency divider, and perform mixing and demodulation to demodulate the frequency of the modulated echo signal. Ultrasonic signal; The processor is used to use a dual-wave method to The ultrasonic signal is processed to obtain the thickness of the measured object.
[0011] As a further optimization, the processor uses a dual-wave method to The ultrasonic signal is processed, including: Obtaining the material of the test piece, and a sound velocity table of ultrasonic longitudinal waves and ultrasonic shear waves in the current test piece material at different integer temperatures; Calculate the sound velocity ratio of ultrasonic longitudinal waves and ultrasonic shear waves at different integer temperatures, and perform linear fitting calculation to obtain the linear ratio expression of the sound velocity ratio; According to the principle of ultrasonic thickness measurement, the thickness of the same test piece at the same temperature is measured using the dual-wave method, and the thickness measurement expression is obtained; Combined with the linear ratio expression of the sound velocity ratio and the thickness measurement expression, the current actual temperature of the measured object is calculated; The ultrasonic longitudinal wave speed and the ultrasonic shear wave speed corresponding to the current actual temperature of the test piece are obtained by using the linear ratio expression of the sound speed ratio; Calculate the actual thickness of the current measured object based on the thickness measurement expression.
[0012] As a further optimization, the linear ratio expression of the sound velocity ratio obtained by linear fitting calculation is: , in, Indicates the ultrasonic longitudinal wave velocity of the current measured material. Indicates the ultrasonic shear wave velocity of the current measured material. and are all constants, is the temperature of the device under test.
[0013] As a further optimization, the thickness measurement expression is: , in, is the actual thickness of the current measured object, is the propagation time of the ultrasonic longitudinal wave in the test piece obtained from the ultrasonic signal, is the propagation time of the ultrasonic shear wave in the test piece obtained from the ultrasonic signal; The thickness measurement expression combining the linear ratio expression of the sound velocity ratio is: , The calculation obtains the current actual temperature of the device under test, which is expressed as: .
[0014] As a further optimization, the method of using the linear ratio expression of the sound velocity ratio to obtain the ultrasonic longitudinal wave speed and ultrasonic shear wave speed corresponding to the current actual temperature of the test piece is: use Get and Corresponding and ; Calculating the actual thickness of the current measured object based on the thickness measurement expression means: will with Corresponding Substitute into the formula Or will Corresponding Substitute into the formula , calculate the actual thickness of the current measured part.
[0015] The beneficial effects of the present invention are as follows: on the one hand, the present invention uses a passive wireless ultrasonic sensor to measure the thickness of the measured object instead of using a traditional active ultrasonic sensor to measure the thickness, which not only reduces the cost waste caused by the use of power supply, but also reduces the safety risk of difficulty in measurement when the measured object is in a high-risk position; on the other hand, because the probe of the passive wireless ultrasonic sensor in the present invention uses a dual-mode probe, it can simultaneously send ultrasonic longitudinal waves and ultrasonic shear waves to the measured object, and after the signal receiving and processing unit receives the echo signal, even if there is temperature fluctuation in the measured object, the thickness of the measured object can be accurately measured, avoiding the problem of low measurement progress when the traditional single-wave method is used for thickness measurement. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 Schematic diagram of an ultrasonic probe and a pipe during manual thickness measurement in the background technology of the present invention; Figure 2 This is a schematic diagram of the ultrasonic thickness measurement principle in the background technology of the present invention; Figure 3 Schematic diagram of the system structure of a passive wireless dual-mode ultrasonic thickness measurement system in Example 1 of the present invention; Figure 4 Schematic diagram of the S-wave and L-wave respectively emitted by the S-wave piezoelectric sheet and the L-wave piezoelectric sheet in the dual-mode ultrasonic probe in the first embodiment of the present invention in the device under test; Figure 5 Schematic diagram of dual-mode ultrasonic signal in embodiment 1 of the present invention. DETAILED DESCRIPTION
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.
[0018] Example 1
[0019] This embodiment provides a passive wireless dual-mode ultrasonic thickness measurement system. The system composition diagram is shown in FIG. Figure 3 , wherein the system mainly includes: A passive wireless ultrasonic sensor is fixedly mounted on the device under test. The probe of the passive wireless ultrasonic sensor is a dual-mode ultrasonic probe. The dual-mode ultrasonic probe includes a longitudinal wave piezoelectric sheet and a transverse wave piezoelectric sheet. After receiving an excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test, ... An excitation unit, configured to send a periodic excitation signal to the passive wireless ultrasonic sensor; The signal receiving and processing unit is used to receive the echo signal, perform demodulation and dual-wave method processing, and obtain the thickness of the measured object.
[0020] In this embodiment, the passive wireless ultrasonic sensor does not require power supply, and the measurement signal (echo signal) of the passive wireless ultrasonic sensor can be obtained wirelessly. Moreover, due to the use of the dual-wave method, the influence of the temperature change of the measured object on the thickness measurement accuracy can be eliminated.
[0021] It should be noted that in order to accurately measure thickness using a passive wireless ultrasonic sensor, in this embodiment, the passive wireless ultrasonic sensor must be mounted on the pipe with its probe perpendicular to the normal of the pipe. Specifically, the passive wireless ultrasonic sensor is fixed to the pipe, and appropriate equipment is used during installation to ensure that the ultrasonic probe is perpendicular to the pipe normal. Even if the installation is not perpendicular, the fixed position of the ultrasonic probe eliminates errors caused by manual manipulation due to the unstable propagation direction of the ultrasonic wave. This is because the corrosion measurement is the difference in wall thickness between two ultrasonic measurements taken at a certain interval.
[0022] In actual applications, the frequency of ultrasonic probes generally used for thickness measurement is between 1 and 10 MHz. If the ultrasonic signal is directly transmitted through an antenna, the antenna size will be too large, which is not conducive to integration and miniaturization. Since the antenna size is proportional to the wavelength, the antenna design generally takes half or a quarter of the signal wavelength. Taking a 5 MHz ultrasonic sensor as an example, the required antenna size is for: , in, is the speed of light, is the signal frequency, is the signal wavelength.
[0023] If the ultrasonic signal is modulated at a high frequency before being transmitted via an antenna, the required antenna size can be significantly reduced. For example, if the ultrasonic signal is boosted to 2.4 GHz, the antenna size can be reduced to 6.25 mm.
[0024] Therefore, in order to reduce the size of the antenna and ensure high-precision thickness measurement, so that the passive wireless ultrasound has practicality, this embodiment provides the following Figure 3 The specific system composition scheme shown.
[0025] See also Figure 3 In this embodiment, the excitation unit includes an ultrasonic excitation source, an oscillator, a frequency divider, a first mixer, a first power amplifier, a second amplifier, a first antenna group, a second antenna group and a third mixer; The ultrasonic excitation source is used to generate a frequency of The ultrasonic excitation signal of multiple cycles is input to the first mixer, and then stops working; The oscillator is always in the transmitting state, and is used to generate a frequency of The high frequency carrier signal is input to the frequency divider; The frequency divider is used to generate frequencies The first signal is input to the first mixer, and after being mixed with the ultrasonic excitation signal in the first mixer, a frequency of The mixed signal is amplified by the first power amplifier and then sent to the third mixer through the first antenna group, and the second signal is amplified by the second power amplifier and then sent to the third mixer through the second antenna group; The third mixer is used to mix the two signals sent by the first antenna group and the second antenna group, and input a frequency of several cycles to the dual-mode ultrasound probe. Ultrasonic excitation signal.
[0026] It should be noted that, in this embodiment, when the dual-mode ultrasound probe receives a periodic frequency of After receiving the ultrasonic excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test; When the ultrasonic shear wave and the ultrasonic longitudinal wave are respectively transmitted in the test piece of the same material and the same temperature, the dual-mode ultrasonic probe senses an echo signal containing the propagation time of the ultrasonic longitudinal wave in the test piece and the propagation time of the ultrasonic shear wave in the test piece.
[0027] Furthermore, the frequency of the echo signal is The echo signal is input to the third mixer, and the echo signal is mixed with the second signal amplified by the second power amplifier and sent through the second antenna group by the third mixer to obtain a frequency of The modulated echo signal is sent to the signal receiving and processing unit via the first antenna group.
[0028] In order to receive and process the echo signal so that the measured thickness is accurate and not affected by the temperature change of the measured object, in this embodiment, the signal receiving and processing unit may include a second mixer and a processor; The second mixer is used to receive the modulated echo signal sent by the first antenna group and the third signal generated by the frequency divider, and perform mixing and demodulation to demodulate the frequency of the modulated echo signal. Ultrasonic signal; The processor is used to use a dual-wave method to The ultrasonic signal is processed to obtain the thickness of the measured object.
[0029] See also Figure 4 In this embodiment, two piezoelectric sheets are provided, corresponding to the longitudinal wave (L wave) piezoelectric sheet and the shear wave (S wave) piezoelectric sheet of the dual-mode ultrasonic probe. The L wave piezoelectric sheet transmits L waves to the device under test, and the S wave piezoelectric sheet transmits S waves to the device under test. In this embodiment, the two piezoelectric sheets share a common excitation unit and signal receiving and processing unit. In the same material and at the same temperature, the propagation speed of the L wave is higher than that of the S wave, so Figure 5 Ultrasonic signals of the two modes are shown.
[0030] In order to accurately calculate the temperature of the measured object and then accurately calculate the thickness of the measured object, in this embodiment, the processor uses a dual-wave method to calculate the temperature of the measured object with a frequency of The ultrasonic signal processing may include: Obtaining the material of the test piece, and a sound velocity table of ultrasonic longitudinal waves and ultrasonic shear waves in the current test piece material at different integer temperatures; Calculate the sound velocity ratio of ultrasonic longitudinal waves and ultrasonic shear waves at different integer temperatures, and perform linear fitting calculation to obtain the linear ratio expression of the sound velocity ratio; According to the principle of ultrasonic thickness measurement, the thickness of the same test piece at the same temperature is measured using the dual-wave method, and the thickness measurement expression is obtained; Combined with the linear ratio expression of the sound velocity ratio and the thickness measurement expression, the current actual temperature of the measured object is calculated; The ultrasonic longitudinal wave speed and the ultrasonic shear wave speed corresponding to the current actual temperature of the test piece are obtained by using the linear ratio expression of the sound speed ratio; Calculate the actual thickness of the current measured object based on the thickness measurement expression.
[0031] In this embodiment, after obtaining the material of the test piece, generally only the ultrasonic longitudinal wave speed and ultrasonic shear wave speed of the current test piece at different integer temperatures can be obtained. However, during the actual operation of the test material, when the temperature fluctuates, it generally does not fluctuate tightly at integer temperatures. Therefore, in order to obtain the ultrasonic longitudinal wave speed and ultrasonic shear wave speed at any temperature within the temperature fluctuation range, a linear fit can be performed on the sound velocity ratio of the ultrasonic longitudinal wave and the ultrasonic shear wave at different integer temperatures. Therefore, in this embodiment, the linear ratio expression of the sound velocity ratio obtained by the linear fitting calculation is: , in, Indicates the ultrasonic longitudinal wave velocity of the current measured material. Indicates the ultrasonic shear wave velocity of the current measured material. and are all constants, is the temperature of the device under test.
[0032] When the material of the test piece is known, in the sound velocity table of ultrasonic longitudinal waves and ultrasonic shear waves at different integer temperatures in the current test piece material, the sound velocity ratio of ultrasonic longitudinal waves and ultrasonic shear waves at different temperatures is different, and the sound velocity ratio of longitudinal waves and shear waves at a certain specific temperature is a constant value. Therefore, the dual-wave method can be used to accurately calculate the actual thickness of the test piece.
[0033] Specifically, the thickness measurement expression can be obtained by using the ultrasonic thickness measurement principle: , in, is the actual thickness of the current measured object, For Figure 5 The propagation time of the ultrasonic longitudinal wave obtained from the ultrasonic signal in the test piece, For Figure 5 The propagation time of the ultrasonic shear wave obtained from the ultrasonic signal in the test piece; At this time, the thickness measurement expression combining the linear ratio expression of the sound velocity ratio is: , At this time, the calculation obtains the current actual temperature of the device under test, which is expressed as: .
[0034] Here, due to and The actual temperature of the measured object can be calculated by taking the known quantity as the actual measured quantity. .
[0035] Finally, use the value corresponding to the actual temperature or , and according to or formula Calculate the actual thickness of the current measured object.
[0036] Therefore, in this embodiment, the use of the linear ratio expression of the sound velocity ratio to obtain the ultrasonic longitudinal wave speed and ultrasonic shear wave speed corresponding to the current actual temperature of the test piece means: use Get and Corresponding and ; Calculating the actual thickness of the current measured object based on the thickness measurement expression means: will with Corresponding Substitute into the formula Or will Corresponding Substitute into the formula , calculate the actual thickness of the current measured part.
[0037] Example 2 Based on Example 1, this example uses a process pipeline in a chemical plant as an example. The process pipeline is made of carbon steel and is wrapped with an insulation layer. During actual operation, the temperature of the pipeline fluctuates between 135°C and 155°C. Within this temperature range, the sound velocity of the L wave and S wave of carbon steel at different integer temperatures and the sound velocity ratio are shown in Table 1: Table 1: Carbon steel L-wave and S-wave sound velocity and sound velocity ratio at different integer temperatures , Assuming the actual pipe thickness is 30mm, since the actual pipe temperature is unknown, the traditional single-wave method can only calculate the wall thickness based on the pipe design temperature, that is, the default pipe temperature is 145°C. If the actual pipe temperature is 135°C or 155°C, the calculated wall thickness using L-wave measurement will be 29.947mm and 30.053mm, respectively; if using S-wave measurement, the calculated wall thickness will be 29.97mm and 30.07mm, respectively. The error between the two methods is very large.
[0038] When the dual-wave method provided in the first embodiment is used to measure the thickness of the pipeline in this embodiment, an accuracy of ±0.01 mm can be guaranteed.
[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A dual-mode ultrasonic thickness measurement system based on passive wireless, characterized by: include: A passive wireless ultrasonic sensor is fixedly mounted on the device under test. The probe of the passive wireless ultrasonic sensor is a dual-mode ultrasonic probe. The dual-mode ultrasonic probe includes a longitudinal wave piezoelectric sheet and a transverse wave piezoelectric sheet. After receiving an excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test, ... An excitation unit, configured to send a periodic excitation signal to the passive wireless ultrasonic sensor; The signal receiving and processing unit is used to receive the echo signal, perform demodulation and dual-wave method processing, and obtain the thickness of the measured object.
2. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 1, characterized in that: When the passive wireless ultrasonic sensor is fixedly mounted on the object under test, the probe of the passive wireless ultrasonic sensor is perpendicular to the normal line of the object under test.
3. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 1, characterized in that: The excitation unit includes an ultrasonic excitation source, an oscillator, a frequency divider, a first mixer, a first power amplifier, a second amplifier, a first antenna group, a second antenna group and a third mixer; The ultrasonic excitation source is used to generate a frequency of The ultrasonic excitation signal of multiple cycles is input to the first mixer, and then stops working; The oscillator is always in the transmitting state, and is used to generate a frequency of The high frequency carrier signal is input to the frequency divider; The frequency divider is used to generate frequencies The first signal is input to the first mixer, and after being mixed with the ultrasonic excitation signal in the first mixer, a frequency of The mixed signal is amplified by the first power amplifier and then sent to the third mixer through the first antenna group, and the second signal is amplified by the second power amplifier and then sent to the third mixer through the second antenna group; The third mixer is used to mix the two signals sent by the first antenna group and the second antenna group, and input a frequency of several cycles to the dual-mode ultrasound probe. Ultrasonic excitation signal.
4. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 3, characterized in that: When the dual-mode ultrasound probe receives a periodic frequency of After receiving the ultrasonic excitation signal, the longitudinal wave piezoelectric sheet generates an ultrasonic longitudinal wave and the transverse wave piezoelectric sheet generates an ultrasonic transverse wave to be transmitted to the device under test; When the ultrasonic shear wave and the ultrasonic longitudinal wave are respectively transmitted in the test piece of the same material and the same temperature, the dual-mode ultrasonic probe senses an echo signal containing the propagation time of the ultrasonic longitudinal wave in the test piece and the propagation time of the ultrasonic shear wave in the test piece.
5. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 4, characterized in that: The frequency of the echo signal is The echo signal is input to the third mixer, and the echo signal is mixed with the second signal amplified by the second power amplifier and sent through the second antenna group by the third mixer to obtain a frequency of The modulated echo signal is sent to the signal receiving and processing unit via the first antenna group.
6. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 5, characterized in that: The signal receiving and processing unit includes a second mixer and a processor; The second mixer is used to receive the modulated echo signal sent by the first antenna group and the third signal generated by the frequency divider, and perform mixing and demodulation to demodulate the frequency of the modulated echo signal. Ultrasonic signal; The processor is used to use a dual-wave method to The ultrasonic signal is processed to obtain the thickness of the measured object.
7. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 6, characterized in that: The processor uses a dual-wave method to The ultrasonic signal is processed, including: Obtaining the material of the test piece, and a sound velocity table of ultrasonic longitudinal waves and ultrasonic shear waves in the current test piece material at different integer temperatures; Calculate the sound velocity ratio of ultrasonic longitudinal waves and ultrasonic shear waves at different integer temperatures, and perform linear fitting calculation to obtain the linear ratio expression of the sound velocity ratio; According to the principle of ultrasonic thickness measurement, the thickness of the same test piece at the same temperature is measured using the dual-wave method, and the thickness measurement expression is obtained; Combined with the linear ratio expression of the sound velocity ratio and the thickness measurement expression, the current actual temperature of the measured object is calculated; The ultrasonic longitudinal wave speed and the ultrasonic shear wave speed corresponding to the current actual temperature of the test piece are obtained by using the linear ratio expression of the sound speed ratio; Calculate the actual thickness of the current measured object based on the thickness measurement expression.
8. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 7, characterized in that: The linear ratio expression of the sound velocity ratio obtained by performing linear fitting calculation is: ， in, Indicates the ultrasonic longitudinal wave velocity of the current measured material. Indicates the ultrasonic shear wave velocity of the current measured material. and are all constants, is the temperature of the device under test.
9. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 7 or 8, characterized in that: The thickness measurement expression is: ， in, is the actual thickness of the current measured object, is the propagation time of the ultrasonic longitudinal wave in the test piece obtained from the ultrasonic signal, is the propagation time of the ultrasonic shear wave in the test piece obtained from the ultrasonic signal; The thickness measurement expression combining the linear ratio expression of the sound velocity ratio is: ， The calculation obtains the current actual temperature of the device under test, which is expressed as: 。 10. The passive wireless dual-mode ultrasonic thickness measurement system according to claim 9, characterized in that: The method of using the linear ratio expression of the sound velocity ratio to obtain the ultrasonic longitudinal wave speed and ultrasonic shear wave speed corresponding to the current actual temperature of the test piece is: use Get and Corresponding and ; Calculating the actual thickness of the current measured object based on the thickness measurement expression means: will with Corresponding Substitute into the formula Or will Corresponding Substitute into the formula , calculate the actual thickness of the current measured part.