Ultrasonic flow meters' advantages and disadvantages

Ultrasonic flow sensor advantage

Ultrasonic flowmeter is a non-contact instrument, which can not only measure the medium flow of large pipe diameter, but also measure the medium that is not easy to contact and observe. Its measurement accuracy is very high. The external clip installation can reach the highest accuracy of ± 0.5%, and it is almost free from the interference of various parameters of the measured medium. In particular, it can solve the flow measurement problems of highly corrosive, non-conductive, radioactive, flammable and explosive media that other instruments cannot.

Ultrasonic flow sensor disadvantages

At present, the main shortcomings are that the temperature range of the measurable fluid is limited by the temperature resistance of the ultrasonic energy transfer aluminum and the coupling material between the transducer and the pipe, and the original data of the measured fluid sound transmission velocity at high temperatures are incomplete. Before 2010, it can only be used to measure fluids below 200 ℃ in China. In addition, the measuring circuit of ultrasonic flowmeter is more complex than that of general flowmeter. This is because the flow rate of liquid in general industrial measurement is usually several meters per second, while the propagation speed of sound wave in liquid is about 1500 m/s, and the maximum change of sound speed caused by the change of flow rate (flow rate) of the measured fluid is also 10-3 orders of magnitude. If the accuracy of measuring flow rate is required to be 1%, the accuracy of measuring sound speed needs to be 10-5~10-6 orders of magnitude, so there must be a perfect measuring line to achieve this, This is the reason why ultrasonic flowmeter can only be applied in practice under the rapid development of integrated circuit technology.

Ultrasonic flowmeter consists of ultrasonic transducer, electronic circuit and flow display and accumulation system. The ultrasonic transmitting transducer converts electric energy into ultrasonic energy and transmits it to the measured fluid. The ultrasonic signal received by the receiver is amplified by the electronic circuit and converted into an electrical signal representing the flow for display and totalizer for display and totalization. In this way, the flow detection and display are realized.

Piezoelectric element of transducer of ultrasonic flowmeter is usually made into circular sheet and vibrates along the thickness. The diameter of the sheet is more than 10 times of the thickness to ensure the directivity of the vibration. Lead zirconate titanate is mostly used as piezoelectric element material. In order to fix the piezoelectric element so that the ultrasonic wave can be injected into the fluid at an appropriate angle, the element needs to be put into the sound wedge to form a whole transducer (also called the probe). The material of sound wedge requires not only high strength and aging resistance, but also small energy loss after ultrasonic passing through the sound wedge, that is, the transmission coefficient is close to 1. The commonly used sound wedge material is plexiglass, because it is transparent, the assembly of piezoelectric components of the sound wedge can be observed. In addition, some rubber, plastic and bakelite can also be used as sound wedge materials.