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.

中文翻译：

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基于容器内壁反射能量变化的超声波液位检测方法

液位检测在工业中发挥着重要作用。对于易燃、易爆、挥发性液体的液位检测，通常采用基于超声波原理的检测方法。尽管付出了很多努力，但检测精度仍然具有挑战性。为了解决检测精度问题，对超声波液位检测方法进行了研究。建立了声束内壁的投影模型。发射-接收探头放置在液罐外壁液位高度附近。探头发出的声束穿过罐壁并在其内壁上产生投影区域。计算探头接收到的回波信号的能量，利用投影区域中液体所占比例与能量的关系来检测液位的变化。搭建测试系统，采集探头接收到的回波信号，并计算其归一化能量。结果表明，对于不同的罐壁厚度、液体类型和检测频率，归一化能量能够清晰地表征液位变化，误差小于3 mm。它为液位检测提供了新途径。研究还表明，对于确定的检测频率，当罐壁厚度对应的值大于或等于探头临界距离时，液位变化的检测精度最高。