是一种非接触式流量计。 The ultrasonic flowmeter is a non-contact flowmeter. The working principle is that when ultrasonic waves propagate in a fluid, their propagation speed is affected by the flow velocity of the fluid. By measuring the velocity of ultrasonic waves in the fluid, the flow velocity of the fluid can be detected and converted into a flow rate. Taking the most widely used time-of-flight ultrasonic flowmeter as an example, when the ultrasonic wave propagates in a fluid, the ultrasonic wave's propagation speed increases in the forward direction and decreases in the countercurrent direction, that is, the same propagation distance has different propagation times. The relationship between the difference between the propagation velocity and the measured fluid velocity is calculated by calculating the velocity and the flow rate. That is, when the ultrasonic beam propagates between the "upstream sensor" and the "downstream sensor" in the direction of the water medium flow in the pipeline, the flow of water will cause a small change in the propagation time of the ultrasonic beam relative to the static propagation, and this propagation time The change is proportional to the flow rate of water. This is the measurement principle of the time difference ultrasonic flowmeter. The theoretical expression of the relationship is as follows:
V = MD / sin2θ × △ T / TupTdown
In the formula, M—the number of linear propagation of ultrasonic beam in water
θ—the angle between the ultrasonic beam and the direction of water flow
Tup—the propagation time of the ultrasonic beam in the positive direction (the propagation time from the upstream sensor to the downstream sensor)
Tdown—the propagation time of the ultrasonic beam in the reverse direction (the propagation time from the downstream sensor to the upstream sensor)
△ T = Tup—Tdown
的特点 Second, the characteristics of ultrasonic flowmeter
Ultrasonic flowmeters are based on micro-processing technology and are mostly designed using integrated circuits and low-voltage wide-pulse emission technology. In terms of measurement technology, in order to achieve higher resolution and larger measurement range, 0.1ns ultra-high-resolution time measurement lines are often used. It is specially used for the measurement of liquid media, especially for water. Its significant features are: accuracy level is ± 1.0%, can be installed under pressure without stopping production, the host can be installed in the value control room and can also output current, pulse and other standard signals and can use RS232 or RS485 interface communication for remote measurement data Send. The flowmeter has the advantages of high reliability, low power consumption, anti-interference, and convenient installation and maintenance.
Problems to pay attention to when using ultrasonic flowmeter
工作原理: 超声波在流动的流体中传播时就载上流体流速的信息。 The working principle of ultrasonic flowmeter : When the ultrasonic wave propagates in the flowing fluid, it carries the information of the fluid velocity. Therefore, the flow velocity of the fluid can be detected by the received ultrasonic wave, and then converted into a flow rate. Ultrasound pulses travel through a pipe from one sensor to another, like a ferryman crossing a river. When the gas is not flowing, the sound pulse travels in both directions at the same speed (speed of sound, C). If the gas in the pipeline has a certain flow velocity V (the flow velocity is not equal to zero), the acoustic pulses traveling in the direction of flow will be transmitted faster, while the acoustic pulses traveling in the direction of flow will be transmitted slower. In this way, the downstream transmission time tD will be shorter and the upstream transmission time tU will be longer. The longer or shorter here are compared with the transmission time when the gas is not flowing; according to the detection method, it can be divided into the propagation speed difference method, Doppler method, beam shift method, noise method and Correlation method and other types of ultrasonic flowmeters. Ultrasonic flowmeter is one that has been applied with the rapid development of integrated circuit technology in the past ten years.