Ultra-Precision Liquid Level Sensing Using Impedance Spectroscopy and Data Analytics

Level sensors find use in various applications for liquid-level monitoring in tanks, containers, and vessels. In this paper, an impedance spectroscopy-based sensing platform has been reported, employing a co-axial sensing probe. The supporting electronics was developed using the MSP 432 microcontroller unit (MCU) from Texas Instruments (TI) and a newly designed Impedance Analyzer-Analog Front End (IA-AFE), also developed at TI. Different signal processing and data processing methods were employed for coaxial probe impedance modeling and their results discussed. The sensor can be used for conductive as well as non-conductive liquids, including liquids with low dielectric constant. Successful measurements of liquid levels were shown for water (E ~ 80) as well as vegetable oil (E ~ 3). The developed sensing platform can measure water level with the accuracy of about 1.2 mm across a 400-mm-long sensing probe while exhibiting a maximum error under 0.6 mm for oil over 150-mm range. The proposed level sensing system provides an accurate and economical solution for level sensing, which is cheaper than the commercially available level sensors while outperforming the accuracy compared with the present state of the art, to the best of our knowledge.