Abstract

Frequency domain reflectometry (FDR) and interferometry are two widely used investigative techniques that have been instrumented using optical and microwave devices for a diverse array of sensing applications. In this paper, we present a highly sensitive liquid-level sensor using a custom hollow coaxial cable transmission line. Measurements of liquid levels with high sensitivity and resolution can be achieved by both FDR and interferometry-based measurements using the same sensor device. We show that FDR-based measurements are more straightforward for liquid-level sensing and are suitable for both small and large variations of liquid level, while interferometry-based measurements provide slightly higher measurement resolution than the FDR-based measurements but require additional data processing and are only suitable for sensing small variations of liquid level. We experimentally demonstrate that the FDR-based measurements exhibit a linear response over a large dynamic range of 122 mm with an estimated resolution of 5 μm. The capability of the proposed sensing system for measurements of multiple levels of a stratified liquid (oil+water) is also investigated based on FDR measurements. The presented work suggests that the two different measurement techniques, namely FDR and interferometry, can be flexibly applied to the proposed coaxial probe for liquid-level sensing, based on different applications.

Department(s)

Electrical and Computer Engineering

Keywords and Phrases

coaxial cable; frequency domain reflectometry; interferometry; liquid-level; microwave sensor

International Standard Serial Number (ISSN)

1557-9662; 0018-9456

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Institute of Electrical and Electronics Engineers, All rights reserved.

Publication Date

01 Jan 2024

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