Real-Time Liquid Level Monitoring With Low-Cost UHF RFID Sensors

This article presents a novel liquid level monitoring system based on passive ultrahigh-frequency (UHF) radio frequency identification (RFID) technology, which is designed to provide low-cost, real-time monitoring. The system uses a novel RFID tag: the front side is used as a sensing tag for liquid level detection, and the back side is used as a reference tag for environmental sensing. Compared to the traditional dual-tag system, this system uses the same two tags, simplifying the design and reducing costs. To improve the measurement accuracy and stability, a multidimensional matrix topological mapping reconstruction (MMTMR) algorithm is proposed, which integrates multiple data dimensions, including collection time, frequency points, experimental conditions, characteristic parameters (the received signal strength indicator (RSSI) and phase of the two tags), liquid level, and number of repetitions, to establish a reliable correlation between the liquid level and the collected data. Experimental results under quantitative, random, and dynamic conditions show that the system is highly adaptable to environmental changes, with a relative error of less than 8.95% and a relative standard deviation (RSD) of less than 3.26%. Compared to the state of the art, the system reduces measurement errors by 4.39%, solving the problems of existing RFID sensors and providing a practical, reliable, and cost-effective solution for various applications.