Liquid level detection of the sealed gas tank based on digital signal processing

Liquefied petroleum gas (LPG) stored in highly-pressured tanks are very commonly used in households in some countries. The current methods for measuring the level of the liquefied gas are mainly based on weight. However, this simple approach can not provide continuous measurement of the level because it can cause the fatigue of the spring in the weight gauge. Although several contact-less detection methods using ultrasonic or acoustic wave have been proposed, they all need to install a transmitter and receiver pair inside the top of the tank. This intrusive approach is not practicable for those millions of tanks been used currently. In this paper, we propose a new method based on another kind of acoustic principle. This approach provides continuous measurement by installing a knocking device outside the tank which can generate acoustic wave for further analysis. Our experimental results show that the frequency of the acoustic wave it generated can be used to estimate the level of the liquefied gas accurately in a very economical way.