A Liquid Level Positioning System For Non-Metal Containers Based on Localized Spoof Surface Plasmon

In this article, a real-time liquid level detection sensor for a non-metal container is presented, which is composed of a spoof surface plasmon polaritons (SSPPs) transmission line and localized spoof surface plasmon (LSSPs) structure. The 14 LSSPs of different sizes have their own resonant frequencies and their responses are independent of each other. By analyzing the offset of the resonance frequencies, the liquid level can be obtained, and the liquid surface tilt angle can be further obtained. Simulations and experiments show that the performance of the sensor is highly dependent on the liquid dielectric constant and the thickness of the container wall. In the case of oil, for example, the maximum penetration depth of the sensor is 3 mm. Using the formula in this article, liquid level tilt angle measurement with an accuracy of up to 1° can be realized. Compared with other types of liquid-level sensors, this sensor can penetrate the container for measurement and has the advantages of high precision, low cost, flexibility, small volume, and measurability of liquid surface tilt angle.