Design of a Novel Ultrasonic Doppler Flow Meter Probe

Abstract: The design information of a new type of ultrasonic Doppler flowmeter probe is provided by excellent flowmeter and flowmeter manufacturers. Abstract: A new type of clamp-on ultrasonic Doppler flowmeter probe suitable for installation on pipelines is introduced. The principle and structure of the ultrasonic Doppler flowmeter sensor, the material, shape, function and important parameters of each main component are introduced in detail. More flowmeter manufacturers select models and price quotations. You are welcome to inquire. The following is the design article details of a new type of ultrasonic Doppler flowmeter probe. A new type of clamp-on ultrasonic Doppler flowmeter probe suitable for installation on pipelines is introduced. The principle and structure of the ultrasonic Doppler flowmeter sensor, the material, shape, function and important parameters of each main component are introduced in detail, and the basic structure, schematic diagram and simulation results of the transmitting circuit of the probe are expounded. It has been proved by practice that the ultrasonic transducer has good and stable performance and has wide application prospects. Introduction The ultrasonic Doppler probe, that is, the transducer, is the sensing element of the Doppler flowmeter. It is usually installed outside the pipeline of the measured fluid, does not touch the measured fluid, does not interfere with the flow of the fluid, has no pressure loss, and is easy to maintain , especially suitable for toxic, harmful, corrosive and abrasive liquids. Its outstanding advantages are that it can achieve high resolution, respond quickly to changes in flow rate, and is insensitive to factors such as fluid pressure, viscosity, temperature, density and conductivity, and has no zero drift problem. It directly affects the measurement accuracy of the flowmeter. Therefore, both the design and manufacturer of the flowmeter and the user department attach great importance to the selection, material, structure, process and installation of the transducer, and are eager to obtain high-precision, stable performance. sensor. 1. Ultrasonic sensor Ultrasonic sensor, also known as ultrasonic transducer, is a device that generates and receives ultrasonic waves, and is an important part of the ultrasonic positioning system. The so-called ultrasonic sensor refers to an electro-acoustic transducer, which is a device or device that can not only convert electrical energy into sound energy, but also convert sound energy into electrical energy. The sensor used to transmit sound waves is called a transmitter. When the sensor is in the transmitting state, the electrical energy is converted into mechanical energy, and then the mechanical energy is converted into sound energy to receive the sound wave. The sensor is called a receiver. When the sensor is in the receiving state, Converts sound energy into mechanical energy and then into electrical energy. The working principle of ultrasonic sensors is basically the same, usually with an electrical energy storage element and a mechanical vibration system. When used as a transmitter, the electrical oscillating signal sent from the output stage of the excitation power supply will cause a change in the electric or magnetic field in the electrical energy storage element in the sensor. The force makes it into a vibrating state, thereby pushing the medium in contact with the mechanical vibration system of the sensor to vibrate, and radiating ultrasonic waves into the medium. The process of receiving ultrasonic waves is just the opposite. In the case of receiving ultrasonic waves, the external ultrasonic waves act on the vibration surface of the sensor, so that the mechanical vibration system of the sensor vibrates, and the electric field or magnetic field in the energy storage element of the sensor is caused by physical effects. A corresponding change occurs, causing the electrical output of the sensor to generate a voltage and current corresponding to the acoustic signal. Obtain the required information through digital processing of voltage or current signals. The ultrasonic Doppler flowmeter probe is manufactured using this principle. 2. Ultrasonic Doppler Flowmeter Probe Structure The external clip-on probe of the ultrasonic Doppler flowmeter does not affect the fluid state of the pipeline during measurement, installation and maintenance, has no flow pressure loss, and is portable and easy to disassemble. The schematic diagram of the probe structure is shown in Figure 1. The probe housing is made of aluminum and has a concave groove, which is easy to be bundled and installed on the outer wall of the pipe with the outer clip of the fixing belt. Piezoelectric transducer wafer adopts piezoelectric ceramic material PsnN-51 with excellent performance. Piezoelectric wafers are thin discs, vibrating along the thickness direction, and the generated ultrasonic waves are longitudinal waves. The piezoelectric ceramic has high sensitivity and Curie temperature, good time stability of various parameters, high dielectric constant and electromechanical coupling coefficient, and is very suitable for ultrasonic Doppler flow measurement in high temperature and high pressure environment. The backing material filled in the probe is made of silica gel, which is a high-impedance, high-attenuation sound-absorbing material, which can absorb the ultrasonic waves radiated from the backside of the piezoelectric transducer wafer and convert it into heat energy, reducing the interference caused by the backside radiation. The matching element is an inductor, which can improve the electromechanical coupling performance between the transmitting and receiving circuits and the piezoelectric transducer wafer. The front end of the chip has an impedance matching layer with a thickness of 1/4 ultrasonic wavelength, which can realize the transition of the acoustic impedance between the transducer chip and the acoustic wedge, and avoid reducing the interface transmission coefficient due to the significant difference in impedance.Avoid the piezoelectric transducer element oscillating with a high Q value to affect the transmitting and receiving performance of the probe. The design of the inclination angle of the acoustic wedge and the selection of the material are to avoid strong reverberation when the ultrasonic wave propagates in the pipeline and fluid, and to improve the signal strength. Polyetherimide (PEI) is used here, and the sound speed c of longitudinal wave propagation at normal temperature (20°C) is 2424m/s. 3. Doppler probe transmitting circuit design and simulation The basic structure of ultrasonic transmitting circuit is shown in Figure 2.

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