How do ultrasonic flow meters work?
Clamp-on ultrasonic flow meters measure the flow rate of liquids or gases. The flow characteristics and the measured medium determine or influence the selection of a suitable and accurate ultrasonic measurement principle.
Ultrasonic waves can propagate through, scatter, or attenuate when encountering different materials, media, or environments. For example, they pass through the air quickly and reflect up to 99% of the signal when hitting a solid surface.
Based on wave transmission principles and material theories, there are two widely researched and applied ultrasonic measurement principles:
Transit Time Measurement Principle
The Transit Time measurement principle measures the time an ultrasonic wave travels from the transmitter to the receiver through the pipe wall and the medium inside. When the flow is moving, the travel time of the wave changes. The device can calculate the flow velocity by comparing the travel time in two opposite directions.
- When the flow opposes the direction of the ultrasonic wave, the wave’s speed decreases, leading to a longer travel time.
- When the flow moves in the same direction as the ultrasonic wave, the wave’s speed increases, resulting in a shorter travel time.
Applications: Transit Time is typically more accurate in applications with clean flow, free from many particles or air bubbles, and is commonly used in industrial applications, clean water systems, and HVAC systems.
Noisetrek Measurement Principle (Doppler Effect)
The Noisetrek principle (based on the Doppler Effect) relies on the change in frequency of the ultrasonic wave when it is reflected by solid particles or air bubbles in the flow. As the liquid flows and carries these solid particles, the frequency of the ultrasonic wave changes after reflection, depending on the flow speed.
Applications: Noisetrek is more suitable for flows containing particles or air bubbles, making it ideal for applications in the oil and gas industry, wastewater, and media containing impurities.
Integrated Solution and Automatic Switching Between the Two Measurement Principles in Flexim Flow Meters
The Flexim Fluxus F721 Series from Flexim–Emerson integrates the Transit Time and Noisetrek (Doppler Effect) principles. The Fluxus F721 offers significant benefits for measuring the flow of various liquids, from clean liquids to those containing impurities or air bubbles, by automatically switching between the two measurement principles:
- High flexibility: Suitable for various applications, from clean water to wastewater, from steady flow to flows with many impurities, even when air bubbles or solid particles make up to 10% of the volume.: Có thể sử dụng trong nhiều loại ứng dụng khác nhau, từ nước sạch đến nước thải, từ dòng chảy ổn định đến dòng chảy có nhiều tạp chất hoặc kể cả khi có hiện tượng bọt khí hoặc chất rắn xâm nhập lên đến 10% thể tích.
- High reliability: Automatic switching between the two principles allows the device to achieve high accuracy and reliability in various flow conditions and helps detect anomalies if they occur during operation.
With these superior features, the Flexim F532/F721 series is the ideal choice for clamp-on ultrasonic flow measurement applications, ensuring high accuracy and reliability in all operating conditions.
Contact us today to learn more about the Flexim solution and optimize your investment costs!
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