200 KHZ Ultrasonic Distance Sensor Matching Layer Materials And Performance Study

With the rapid development of science and technology,ultrasonic wave has been widely concerned by researchers because of its good directivity,penetration and anti-interference ability.Ultrasonic transducer is the key to the application of ultrasonic technology.It is a device that transmits and receives ultrasonic waves by using the ultrasonic characteristics of piezoelectric elements.There is a certain acoustic impedance mismatch between the piezoelectric element of the transducer and the detection target,which leads to the phenomena of reverberation,spontaneous heat,low signal-to-noise ratio and signal distortion in the transducer.Therefore,in order to improve the performance of the ultrasonic transducer,it is necessary to add a matching layer in the device to reduce the acoustic mismatch,and increase the coupling between the transducer and the medium through the effective impedance acoustic transition.Because the performance of domestic ultrasonic distance sensor is much lower than that of similar imported products,this paper,aiming at the matching problem of piezoelectric elements for domestic sensing,studies the industrial preparation scheme of matching layer and the assembly and performance optimization of ultrasonic transducer.In order to meet the needs of industrial production and ultrasonic distance sensing,this paper selects 200 khz PZT-5 lead zirconate titanate piezoelectric ceramics commonly used in the market and with the frequency range closest to imported products as the piezoelectric vibrator of ultrasonic transducer.Four types of hollow glass microspheres k1,k20,k25 and s32 produced by 3M Company and commercial epoxy resin were used as bonding materials to prepare the matching layer.On the basis of screening epoxy resins with suitable viscosity and curing properties,the influence of preparation technology on the properties of matching layer was explored.The impedance characteristic curves of piezoelectric ceramic before and after the matching layer were compared by impedance analyzer,and the influence of the thickness of matching layer and packing concentration on the impedance of ultrasonic transducer probe was tested and analyzed.It is found that due to the influence of paste technology,the thickness of matching layer does not strictly follow the principle of quarter wavelength in practical application,so it needs to be strictly screened according to the actual technology to achieve the best matching effect.The matching layer packing concentration has little influence on the resonant frequency and anti-resonant frequency of the transducer,but it will make the difference between the positive and negative resonant frequencies change greatly.The matching layer performance is optimal when the difference is about 60 khz.Part of the circuit of the ultrasonic transducer is designed.By building the performance test platform of the ultrasonic transducer,the ultrasonic transducer probe whose performance meets the standard is loaded into the ultrasonic sensor test platform for testing,and the echo signal diagram of the ultrasonic transducer is obtained.The distance between the metal reflecting plate and the ultrasonic transducer probe is read directly through the external ammeter.Through multiple process control,the ultrasonic sensing distance of the sensor prepared by using the optimal piezoelectric element developed in this paper can reach 1.8 meters,which is 1.5 times of the domestic similar products,and the performance is close to the imported similar products.The sensor is expected to reach or even exceed the imported similar sensor after optimizing the backing material,paste process and packaging process,and realize the localization replacement of such sensor products.The research content of this paper has certain guiding significance for the preparation of similar sensor matching layer and the production of sensor.