Ultrasonic flowmeter is a device that uses the principle of velocity difference method to measure the flow of liquid in the pipe. It can be divided into external clamp type and pipe segment type. It is often used in combination with digital signal processing technology, multi-pulse technology, error correction technology, etc. to adapt to the environment and enhance its reliability. It has been widely used in chemical industry, electric power, petroleum, metallurgy and other fields.
Ultrasonic flowmeter is mainly composed of ultrasonic generator, ultrasonic receiver, electronic circuit, flow display and accumulation system. Among them, the ultrasonic generator is mainly used to generate ultrasonic waves and emit them into the fluid; the ultrasonic receiver is mainly used to receive ultrasonic waves after passing through the fluid; after the ultrasonic waves are received, they are amplified and converted by the electronic circuit, and then the flow is transmitted to the display screen in the form of electrical signals and the results are displayed; the accumulation system completes the accumulation calculation of the flow.
The ultrasonic flowmeter measures the liquid flow by detecting the effect of fluid flow on ultrasonic waves, which uses the "time difference method".
First, probe 1 is used to transmit a signal, and the signal passes through pipe wall 1, fluid, and pipe wall 2 and is received by probe 2 on the other side; while probe 1 transmits a signal, probe 2 also sends the same signal, which is received by probe 1 after passing through pipe wall 2, fluid, and pipe wall 1; due to the existence of flow velocity, the two times are not equal, and there is a time difference, so the flow velocity can be obtained according to the time difference, and then the flow value can be obtained.
Since the ultrasonic flowmeter uses ultrasonic waves to measure the flow of fluids, it can not only measure the flow of conventional pipelines, but also measure the flow of pipelines that are difficult to observe and difficult to touch; it can not only measure the flow of conventional fluids, but also measure the flow of fluids with strong corrosive, radioactive, flammable, and explosive characteristics.
The range of ultrasonic measurement of fluid flow is so wide, but it also has its disadvantages. Ultrasonic flowmeters have limitations on the temperature range of the measured fluid. Currently, ultrasonic flowmeters in my country can only be used to measure fluids below 200°C. Moreover, the measurement circuit of ultrasonic flowmeters is quite complex. If the measurement result accuracy is required to be 1%, the measurement accuracy of the sound velocity must reach the order of 10-5 to 10-6, which places high requirements on the measurement circuit.