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Ultrasonic flowmeters are already widely used in people’s lives. Their advantages are obvious to all, but have people identified any disadvantages of ultrasonic flowmeters? Only by understanding the advantages and disadvantages can improvements be made. Next, our technical staff from Shanghai Automation Instrument Co., Ltd. will introduce to you the disadvantages of ultrasonic flowmeters. The main disadvantages of ultrasonic flowmeters are that the temperature range of the fluid that can be measured is limited by the temperature tolerance of the ultrasonic transducer and the coupling material between the transducer and the pipe, as well as the lack of accurate data regarding the sound propagation speed of the fluid at high temperatures. At present, in our country it can only be used to measure fluids below 200°C. Furthermore, the measurement circuit of an ultrasonic flowmeter is more complex than that of a conventional flowmeter. This is because, in general industrial measurement applications, the flow velocity of liquids is often several meters per second, while the speed of sound in liquids is around 1500 m/s. The maximum change in the speed of sound caused by variations in the flow velocity (or flow rate) of the fluid is on the order of 10^-3. If a precision of 1% is required for measuring the flow velocity, then the precision needed for measuring the speed of sound must be on the order of 10^-5 to 10^-6. Therefore, a sophisticated measurement system is necessary to achieve this, and this is precisely why ultrasonic flowmeters can only be put into practical use with the rapid development of integrated circuit technology. An ultrasonic flow meter consists of an ultrasonic transducer, electronic circuitry, and a flow display and accumulation system. The ultrasonic transmitting transducer converts electrical energy into ultrasonic energy, which is then emitted into the fluid to be measured. The ultrasonic signals received by the receiver are amplified by electronic circuits and converted into electrical signals representing flow rate, which are fed to display and accumulation instruments for display and calculation. This enables the detection and display of traffic. Ultrasonic flowmeters commonly use piezoelectric transducers. It utilizes the piezoelectric effect of piezoelectric materials; an appropriate transmission circuit is used to apply electrical energy to the piezoelectric elements of the transmitting transducer, causing it to generate ultrasonic vibrations. Ultrasonic waves are transmitted into the fluid at a certain angle, then captured by a receiving transducer, and converted into electrical energy via piezoelectric elements for detection. The transmitting transducer utilizes the inverse piezoelectric effect of piezoelectric elements, while the receiving transducer makes use of the piezoelectric effect. The piezoelectric elements of ultrasonic flowmeter transducers are typically made into circular thin sheets that vibrate along their thickness. The diameter of the thin sheet should be more than 10 times its thickness to ensure the directivity of vibration. Lead zirconate titanate is commonly used as the material for piezoelectric elements. To fix the piezoelectric element and direct ultrasonic waves into the fluid at an appropriate angle, the element must be placed within an acoustic wedge to form the entire transducer (also known as the probe). The material of the acoustic wedge is required not only to have high strength and resistance to aging, but also to result in minimal energy loss of ultrasonic waves passing through it, meaning that the transmission coefficient should be close to 1. The commonly used material for acoustic wedges is plexiglass, as it is transparent, allowing one to observe the assembly of the piezoelectric elements within the acoustic wedge. Additionally, certain rubbers, plastics, and bakelite can also be used as sound wedge materials. These are the disadvantages of ultrasonic flowmeters; some of them can be addressed through technical improvements, while others are inherent flaws in the product itself. Everyone can keep proposing ways to make improvements, and it is believed that the disadvantages of ultrasonic flowmeters will gradually decrease.