When the working temperature is high, some liquids are prone to produce steam or mist. Since the steam is lighter than air, it floats to the top of the tank and forms a layer of vapor that absorbs and scatters the ultrasonic pulse. We know that the transmission attenuation of ultrasonic waves in steam is obvious. It should be said that it is difficult to penetrate. Once the measurement space has steam or aerosol generation, it may prevent the ultrasonic waves from reaching the measuring surface and reflecting back, so the ultrasonic level gauge is not suitable for Use on liquids that may generate steam or aerosols. By installing static tubes, the influence of the vapor layer on the measurement can be reduced or reduced.
2. The bubble
The dry foam and wet foam can reflect the ultrasonic wave back, so the ultrasonic liquid level gauge is used to measure no effect; the neutral foam will absorb and diffuse some ultrasonic waves, which will weaken the reflection of the ultrasonic wave and cause the echo to be unstable. Therefore, when the surface of the medium is thick and thick foam, the measurement error of the ultrasonic liquid level gauge will be large and even impossible to measure.
The speed of sound cannot be transmitted in a vacuum, and the essence of ultrasonic waves is a kind of sound wave, and belongs to a mechanical wave, so it cannot propagate in a vacuum either. Although pressure factors alone have little effect on the measurement of ultrasonic level gauges, pressure changes will not directly affect the transmission of ultrasonic waves. However, changes in pressure will cause changes in temperature, which in turn will affect the transmission rate of ultrasonic waves. , has an effect on the measurement of the liquid level.