The Method of Measuring Liquid Level by Acoustic Level Sensor in Sewage Treatment Plant

Waste water discharged from polluted sources, because of its high total amount or concentration of pollutants, which cannot meet the requirements of discharge standards or environmental capacity so as to reduce the quality of water environment and functional objectives. This place which must be strengthened manually is a sewage treatment plant, also known as a sewage treatment station. With the rapid development of China's economy and the increase of industrialization, the pollution of water resources is also aggravating, especially the increasing discharges of urban sewage and industrial sewage, which result in increasingly serious water pollution. The country pays more and more attention to the protection of water resources, and strengthens the treatment of urban sewage and industrial sewage. It puts forward higher requirements for achieving the best effect of various sewage treatment processes, normal operation of treatment equipment, accurate monitoring of water quality and quantity of sewage treatment. In this situation, the life and industrial sewage treatment process is also constantly improving. Many cities have established sewage treatment plants.

The sewage treatment rate has increased significantly, and the environment of the water has gradually improved. With the rapid development and popularization of computer technology, data acquisition system has been rapidly used. This system can be used to collect, monitor and record the process parameters on the production site, and provide information and means for improving product quality and reducing cost.Data acquisition is to collect analog signals from sensors and convert them into digital signals recognized by computers for further processing.

Nowadays, with the development of digital liquid measuring device, various types of liquid level meters have appeared. There are glass plate level gauges made by the principle of connectors, magnetic flip plate level gauges made by adding magnetic floats through the principle of magnetic coupling, liquid level transmitters for measuring liquid differential pressure, ultrasonic flow level gauges made by the principle of ultrasonic reflection and so on. This article introduces the method of liquid level measurement by ultrasonic pressure sensor for liquid level in sewage treatment plant. In the process of sewage treatment, the ultrasonic pressure sensor for liquid level is used to detect the liquid level deviation by the reflection principle of ultrasound at the liquid level, that is, the echo measuring distance principle. When the ultrasonic probe emits a short ultrasonic pulse to the liquid surface, after time T, the probe receives the echo pulse reflected back from the liquid surface. Therefore, the distance from the probe to the liquid surface can be calculated by the following formula: the distance from the ultrasonic probe to the bottom of the container is h, the actual liquid level will be determined. In the formula, V is the velocity of ultrasonic wave propagating in the medium under test (i.e. the velocity of sound m/s).

It is shown that the liquid level H can be calculated by measuring the time accurately as long as the velocity of sound V is known. It can be seen that ultrasonic measurement is a method to measure the storage of containers by measuring the material level. The ultrasonic sensor transmits the ultrasonic pulse from the material surface and receives the echo reflected from the surface. It measures the propagation time of ultrasound and calculates the distance from the reflecting surface. The propagation time is the direct dimension of the distance between the ultrasonic sensor and the level. The propagation distance of sound wave is the product of propagation time and sound velocity. If the location of the ultrasonic sensor is known, then the level (and reserves) can be calculated. Sound velocity varies widely in the air. Therefore, the acoustic sensor needs temperature compensation. If it is used in other gases besides air, it should be calibrated accordingly.
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