CN117705240B - Ultrasonic water meter workpiece detection system capable of achieving high-precision calibration - Google Patents

Abstract

The invention relates to the technical field of ultrasonic transducers and discloses an ultrasonic water meter workpiece detection system capable of realizing high-precision calibration. The transducer of the transmitting end and the receiving end of the cylinder are arranged below and above the object to be measured. The couplant enables the transducer to fully contact the object to be measured. The transmitting and receiving circuits are electrically connected to the transducers. The system calibration method is as follows: the lower pressure receiving end transducer stores absolute flight time and signal amplitude when a received signal larger than a threshold appears; continuously pressing down, and storing the absolute flight time and the signal amplitude value every time the absolute flight time is reduced by a fixed value; stopping collecting and pressing down when the absolute flight time is reduced to a threshold value; and finding out the optimal coupling state and corresponding to absolute flight time, and starting detection at the position where the change rate of the signal amplitude is smaller than the threshold value. The invention eliminates the influence of the initial coating of the couplant by selecting the system composed of the transducer and the couplant, and realizes the high-precision calibration of the probe.

Description

An ultrasonic water meter workpiece detection system capable of achieving high-precision calibration

Technical Field

The invention relates to the technical field of ultrasonic transducers, and in particular to an ultrasonic water meter workpiece detection system capable of realizing high-precision calibration.

Background technique

The reflectivity of ultrasound at the interface is an important parameter to characterize the acoustic coupling performance. The greater the reflectivity, the worse the coupling performance. For ultrasonic coupling agents, the interface reflectivity is not only affected by the acoustic impedance between the coupling agent and the material being tested, but also by the interface roughness and coupling pressure. The coupling agent is in direct contact with the surface of the workpiece to be tested, and a coupling interface is formed under pressure. Ultrasonic waves are transmitted to the workpiece through the interface to achieve detection. Affected by the roughness of the interface, if the applied pressure is not enough to form an ideal coupling interface, a small amount of air will remain in the interface. The acoustic impedance of air is much lower than the acoustic impedance of the interface, which will cause a serious mismatch in the coupling impedance and fail to achieve the ideal sound transmission effect. By controlling the applied load to control the state of the solid coupling agent, the residual air is removed to achieve good coupling, but the thickness of the initially applied coupling agent is difficult to control to be exactly the same. Furthermore, even if the thickness of the coupling agent is the same, due to the influence of factors such as the resonant frequency and impedance phase deviation between different transducers, there will be differences in signal strength. Therefore, it is of great significance to design a workpiece monitoring system that can achieve high-precision calibration of the probe.

Summary of the invention

In view of the shortcomings of the existing ultrasonic solid-state coupling probe technology, the present invention proposes an ultrasonic water meter workpiece detection system that can achieve high-precision calibration, eliminates the influence of the initial coating of the solid coupling agent on the detection accuracy, and can achieve high-precision calibration of the probe.

The purpose of the present invention can be achieved through the following technical solutions.

An ultrasonic water meter workpiece detection system capable of realizing high-precision calibration is characterized in that it comprises four parts: a transmitting end ultrasonic transducer, a receiving end ultrasonic transducer, a silicone solid coupling agent, and an ultrasonic transmitting and receiving circuit.

The shape of the ultrasonic transducer at the transmitting end is cylindrical, with a silicone solid coupling agent coated on the surface. When in use, it is installed below the object to be measured.

The receiving end ultrasonic transducer is cylindrical in shape, with a silicone solid coupling agent coated on the surface. It is installed above the object to be measured when in use.

The silicone solid coupling agent makes the ultrasonic transducer fully contact with the object to be measured. It uses soft silicone with a coating thickness of 1mm.

The ultrasonic transmitting and receiving circuits are electrically connected to the transmitting end ultrasonic transducer and the receiving end ultrasonic transducer respectively, and are used for generating excitation signals of the transmitting end ultrasonic transducer, processing received signals of the receiving end ultrasonic transducer, and calculating absolute flight time.

The calibration method of the workpiece detection system includes the following steps.

S1: Press down the receiving end transducer at a uniform speed and monitor the received signal. When the received signal greater than 100mV appears for the first time, collect and store the corresponding absolute flight time and received signal amplitude.

S2: Continue to press down the receiving end transducer. Every time the absolute flight time decreases by 62.5ns, the corresponding absolute flight time and the received signal amplitude are collected and stored.

S3: When the absolute flight time decreases to 1000ns, stop collecting and pressing down the transducer at the receiving end.

S4: Analyze the stored information to find the absolute flight time corresponding to the best coupling state, and use the position where the received signal amplitude change rate is less than 0.5 as the starting detection position after calibration.

Preferably, the ultrasonic signal emitted by the transmitting-end ultrasonic transducer passes through the transmitting-end ultrasonic transducer silicone solid coupling agent, the object to be measured, and the receiving-end ultrasonic transducer silicone solid coupling agent to reach the receiving-end ultrasonic transducer.

Preferably, the Shore hardness of the silicone solid coupling agent is 25A.

Preferably, the excitation signal frequency generated by the ultrasonic transmitting and receiving circuit is 2 MHz, and the number of pulses is 10; during each detection, the ultrasonic transmitting and receiving circuit controls the change in absolute flight time between the transmitted and received ultrasonic signals to be the same, so as to ensure that the compression stroke of the silicone is the same each time, thereby making the mechanical pressure applied during each detection the same, thereby eliminating the influence of the silicone solid coupling agent on the detection.

Preferably, the absolute flight time when the rate of change of the signal amplitude with time under the current ultrasonic transducer tends to be stable is used for calculation each time for detection, so as to ensure that the state of the silicone after being pressed down is in the best coupling state each time for detection.

The standard for the rate of change of the signal amplitude over time to tend to be stable is that the rate of change of the amplitude of the signal received 10 times continuously at the starting detection position after calibration is less than 0.5.

The beneficial effects of the present invention are as follows: by selecting a system consisting of an ultrasonic transducer with a frequency of 2 MHz and a silicone solid coupling agent with a hardness of 25A and a coating thickness of 1 mm, the influence of the initial coating of the solid coupling agent on the detection accuracy is eliminated, and high-precision calibration of the probe can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view of the system of the present invention.

FIG. 2 is a discrete curve showing how the amplitude of a received signal varies with the absolute flight time in an embodiment of the present invention.

Figure numerals: 1 is a transmitting end ultrasonic transducer, 2 is a receiving end ultrasonic transducer, 3 is a silicone solid coupling agent, 4 is a workpiece to be measured, and 5 is an ultrasonic transmitting and receiving circuit.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

Embodiment: As shown in FIG1 , an ultrasonic water meter workpiece detection system capable of high-precision calibration includes a receiving end ultrasonic transducer 2, which is used to receive 2MHz ultrasonic signals and can move up and down in the vertical direction. When the receiving end ultrasonic transducer 2 moves downward to the surface of the workpiece 4 to be measured under pressure, the silicone solid coupling agent 3 fully contacts the surface of the workpiece 4 to be measured, and applies downward pressure to the workpiece 4 to be measured, and the pressure makes the workpiece 4 to be measured fully contact with the silicone solid coupling agent 3 of the ultrasonic transducer of the transmitting end; the ultrasonic transducer 1 of the transmitting end is used to generate a 2MHz ultrasonic signal, which belongs to high-frequency ultrasonic waves, has a relatively short wavelength, strong reflection performance, and has higher detection accuracy. The generated ultrasonic signal passes through the silicone solid coupling agent of the transmitting end transducer, the workpiece 4 to be measured, and the silicone solid coupling agent of the receiving end transducer to reach the receiving end; the silicone solid coupling agent 3 has a Shore hardness of 25A, a fast curing speed, extremely low hardness and excellent bonding strength, and good elasticity after curing and molding, and can achieve full contact with the matching layer after being subjected to pressure. The thickness of the coated silicone is controlled to be 1mm. The greater the thickness, the more absorption and scattering attenuation of the ultrasonic wave, and the smaller the received sound pressure peak value; if the thickness is too small, the coupling effect with the matching layer is poor. The ultrasonic transmitting and receiving circuit 5 is used to generate an excitation signal for the ultrasonic transducer 1 at the transmitting end. The excitation signal frequency is 2MHz and the number of pulses is 10. The receiving circuit processes the signal received from the ultrasonic transducer 2 at the receiving end to realize the calculation of the absolute flight time, thereby realizing the control of the applied load.

The principle and process of injection molding quality inspection are as follows.

S1: The ultrasonic transducer 1 at the transmitting end is stimulated by an electrical signal to generate a 2MHz high-frequency vibration and generate an ultrasonic signal.

S2: The ultrasonic signal is transmitted to the workpiece 4 to be measured through the silicone solid coupling agent 3.

S3: When an ultrasonic signal encounters an interface composed of media with different acoustic impedances (bubbles), it is scattered, which reduces the energy in the original propagation direction and attenuates the signal intensity.

S4: The ultrasonic transducer 2 at the receiving end converts the received ultrasonic signal into an electrical signal and then processes the signal through the ultrasonic transmitting and receiving circuit 5, and judges the injection molding quality of the workpiece 4 to be tested by the magnitude of the signal amplitude.

The essence of the load applied during detection by the transducer solid-state coupling probe is that the pressure changes the thickness of the silicone and the degree of contact between the silicone and the rough surface of the object to be measured. Since the thickness of the workpiece 4 to be measured is constant, the propagation speed of sound in the silicone and the workpiece 4 to be measured is a constant, so the change in the length of the sound path is only related to the change in the thickness of the silicone.

ΔD=ΔL=（ΔT×V）/2.

Among them, ΔD is the change in the length of the sound path, ΔL is the change in the thickness of the silicone, ΔT is the absolute flight time of the ultrasonic wave from emission to reception, and V is the speed of ultrasonic wave propagation in the object.

Since the thickness of the workpiece 4 to be measured is constant, the propagation speed of sound in the silicone and the matching layer is a constant, so the sound path is only related to the thickness of the silicone, and the thickness of the silicone actually reflects the size of the applied load.

The surface roughness and internal properties of the initial silicone rubber of the different probes are always different, so the thickness when reaching the optimal coupling state during the load application process corresponds to different absolute flight times. During the pressing process, the applied load gradually increases, the silicone thickness gradually decreases, the absolute flight time gradually decreases, and the signal strength gradually increases and tends to be stable. In order to adjust the state of the silicone after pressing down to the optimal coupling state each time the measurement is made. During the detection, the absolute flight time T1 where the rate of change of the signal amplitude of different probes over time tends to be stable is found.

The calibration steps are as follows.

S1: Press down the receiving end ultrasonic transducer 2 at a constant speed, monitor the changes in absolute flight time and signal strength, and start collecting from the appearance of the signal (>100mV).

S2: Continue to press down the upper tooling, starting from the absolute flight time between the receiving and transmitting ultrasonic transducers at 100mV, collect the amplitude of the receiving transducer signal every time the absolute flight time decreases by 62.5ns, and store all the absolute flight times collected during the pressing process and the corresponding signal amplitude information.

S3: When the absolute flight time decreases to two cycles (1000ns), stop collecting and stop pressing down the upper tooling.

S4: Analyze the stored information: find the absolute flight time corresponding to the best coupling state, and take the position where the curvature of the discrete curve of signal amplitude versus absolute flight time is less than 0.5 as T1. Subsequent detection starts from T1, and the discrete curve in the embodiment is shown in FIG2.

The above embodiments are descriptions of specific implementation methods of the present invention rather than limitations of the present invention. Technical personnel in the relevant technical field may make various changes and modifications to obtain corresponding equivalent technical solutions without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims (5)

1. The utility model provides an ultrasonic water meter work piece detecting system that can realize high accuracy calibration which characterized in that includes transmitting end ultrasonic transducer, receiving end ultrasonic transducer, silica gel solid-state couplant, ultrasonic wave transmission and receiving circuit 4 parts, wherein:

the ultrasonic transducer at the transmitting end is in a cylinder shape, and the surface of the ultrasonic transducer is coated with a silica gel solid coupling agent and is arranged below an object to be measured in use;

the receiving end ultrasonic transducer is in a cylinder shape, and the surface of the receiving end ultrasonic transducer is coated with a silica gel solid coupling agent and is arranged above an object to be measured in use;

The silica gel solid coupling agent enables the ultrasonic transducer to be fully contacted with an object to be detected, soft silica gel is adopted, and the coating thickness is 1mm;

The ultrasonic wave transmitting and receiving circuit is respectively and electrically connected with the transmitting end ultrasonic transducer and the receiving end ultrasonic transducer and is used for generating an excitation signal of the transmitting end ultrasonic transducer, processing a receiving signal of the receiving end ultrasonic transducer and calculating absolute flight time;

The calibration method of the workpiece detection system comprises the following steps:

S1: pressing down the receiving end transducer at a constant speed, monitoring a received signal, and collecting and storing corresponding absolute flight time and received signal amplitude when the received signal with the amplitude of more than 100mV appears for the first time;

S2: continuously pressing down the pressure receiving end transducer, and collecting and storing corresponding absolute flight time and received signal amplitude once every 62.5ns of absolute flight time is reduced;

S3: stopping collecting the downward pressure of the energy converter at the receiving end when the absolute flight time is reduced to 1000 ns;

S4: and analyzing the stored information, finding the absolute flight time corresponding to the optimal coupling state, and taking the position with the amplitude change rate of the received signal less than 0.5 as the initial detection position after calibration.

2. The ultrasonic water meter workpiece detection system capable of achieving high-precision calibration according to claim 1, wherein an ultrasonic signal sent by the ultrasonic transducer at the sending end passes through the silica gel solid couplant at the ultrasonic transducer at the sending end, an object to be detected and the silica gel solid couplant at the ultrasonic transducer at the receiving end to reach the ultrasonic transducer at the receiving end.

3. The ultrasonic water meter workpiece detection system capable of achieving high-precision calibration according to claim 1, wherein the shore hardness of the silica gel solid coupling agent is 25A.

4. The ultrasonic water meter workpiece detection system capable of realizing high-precision calibration according to claim 1, wherein the frequency of an excitation signal generated by the ultrasonic wave transmitting and receiving circuit is 2MHz, and the pulse number is 10; when each detection is performed, the change amount of absolute flight time between the ultrasonic signals transmitted and received is controlled to be the same through the ultrasonic transmission and receiving circuit, so that the same compression stroke of the silica gel is ensured each time, the same mechanical pressure is applied each time of detection, and the influence of the silica gel solid coupling agent on detection is eliminated.

5. The ultrasonic water meter workpiece detection system capable of realizing high-precision calibration according to claim 1, wherein the absolute flight time when the change rate of the signal amplitude of the current ultrasonic transducer with time tends to be stable is calculated at each detection, so as to ensure that the state of the silica gel after being pressed down is in an optimal coupling state at each detection;

the criterion that the rate of change of the signal amplitude over time tends to be stable is that the rate of change of the amplitude of the received signal is less than 0.5 for 10 consecutive times at the initial detection position after calibration.