1 Overview
In recent years, China has proposed a building energy-saving plan and gradually realized a household metering and charging system. Heating metering is gradually becoming a hot spot in technology research, and household ultrasonic thermometers are attracting more and more attention with low power consumption and high precision. Ultrasonic flow measurement achieves non-contact high-precision measurement, so it has the advantages of wide range, no pressure loss, simple composition and high sensitivity. The current major ultrasonic flow measurement techniques are the time difference method and the phase difference method. The time difference method ultrasonic flowmeter is measured according to the linear relationship between the flow velocity and the time difference of the medium. As long as the forward flow time is accurately determined, the instantaneous flow velocity can be obtained according to the linear relationship between the flow velocity and the instantaneous flow rate. The phase difference rule is to obtain the phase difference information of the forward-flow echo signal by a certain technical means, and to calculate the propagation time difference of the ultrasonic forward flow. In August 2014, Beijing Meikecore Technology Co., Ltd. and US ICCI jointly released the industry's first intelligent ultrasonic heat meter special chip UTA6905 based on phase difference method. This paper mainly introduces the phase difference method ultrasonic flow metering principle of UTA6905 chip.
2. Phase difference method ultrasonic flow metering principle phase difference method
The ultrasonic heat meter measuring system uses the ultrasonic phase difference method to measure the flow value in the current pipeline, and uses the temperature sensor to measure the inlet water temperature and the outlet water temperature, and the heat calculation can be used to obtain the heat used in the current residence. The UTA6905 chip uses the phase difference method to measure the flow in the pipeline by measuring the difference in phase shift between the upstream and countercurrent propagation of the ultrasonic wave. The principle of ultrasonic flow measurement is shown in Figure 1.
Figure 1: Principle of ultrasonic flow measurement
In Figure 1, the diameter of the flow pipe is D, the horizontal distance between the two transducers is L, the transmission speed of the ultrasonic wave in water is c, and the velocity of the fluid in the pipe is v, and the transit time t1 of the ultrasonic wave in the downstream can be obtained. The transit time t2 during the countercurrent propagation process is:
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