Several issues on the use of ultrasonic level meters in rainwater treatment at subway stations

　　Ultrasonic level meters have the characteristics of non-contact measurement and easy installation. They are widely used in the field of liquid level measurement. However, they still have many limitations. Let's talk about their application in rainwater treatment at Shanghai Metro Line 9 stations.

　　In this project, the design unit designed and adopted the currently more commonly used ultrasonic level meter to monitor the rainwater level, so as to control the start and stop of the drainage pump.

　　During the actual construction process, many problems were encountered. First, the sizes of rainwater collection pools were different, and the situation below the reserved holes on the pool cover was complicated. Or after the ultrasonic level meter was installed, the signal could not be recognized, and so on.

　　The installation of ultrasonic level meter in a large pool is relatively convenient and there are not many problems in its use. However, some pools are less than 1 meter deep, and the blind area of ​​ultrasonic level meter is 0.3 meters. Party A does not allow the pool to be open. Finally, such small pools cannot be installed with ultrasonic level meter, or after installation, they are flooded, and a submersible level meter has to be used as a substitute. Some installation company staff even suggested using a float instead.

　　In some pools, ultrasonic level meters were required to be installed under the covers, but these level meters were not able to escape the fate of being flooded.

　　In some pools, the ultrasonic level meter works fine outside, but is always in the searching state after being installed in the pool. The problem is solved after using the waveguide.