Liquid level detection plays an important role in industry. For the liquid level detection of flammable, explosive and volatile liquids, the detection method based on the ultrasonic principle is usually adopted. Though a lot of efforts, the detection precision is still challenging. Herein, Ultrasonic liquid level detection method is studied to address the detection precision. A projection model of the inner wall of the sound beam is established. The transmitter-receiver probe is placed near the height of the liquid level on the outer wall of the liquid tank. The sound beam emitted by the probe passes through the tank wall and generates a projection area on its inner wall. The energy of the echo signal received by the probe is calculated, and the relationship between the proportion of liquid in the projection area and the energy is used to detect changes in the liquid level. The test system is set up, the echo signal received by the probe is collected, and its normalized energy is calculated. The results show that for different tank wall thicknesses, liquid types and detection frequencies, the normalized energy can clearly characterize the change of liquid level with an error of less than 3 mm. It provides a new avenue for liquid level detection. The research also shows that for the determined detection frequency, when the tank wall thickness corresponds to the values greater than or equal to the critical distance of the probe, the detection accuracy of liquid level change is the highest.
Keywords: Echo energy; Liquid level detection; Ultrasonic wave.
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