ラム波を用いた液面レベルセンシングの検討

抄録

We examined the possibility of applying Lamb waves as a liquid level sensing method utilizing ultrasonic guided waves. Using the difference in the propagation speed of Lamb waves, which propagate when the plate is in contact with air, and Scholte waves, which propagate when the plate is in contact with a liquid, the authors experimentally demonstrated that the liquid level can be determined from the propagation time. The wavelet transform was applied to analyze the Lamb wave's propagation time, and the wavelet coefficient peak corresponding to the excitation frequency was used as the propagation time. When the liquid level is low, there is a region where a large error in the propagation time is detected due to interference between the 1st echo of the Lamb wave and the echo reflected from the liquid surface. If the sensor is used without such an area, it can be operated with a resolution and accuracy of 0.5 ± 0.77 mm.