Development of a microwave displacement sensor for hydraulic devices

The paper presents the fundamentals, design, realization and characterization of a state-of-the-art microwave (μW) based piston position detection sensor (PPDS) for stationary or moving pistons in hydraulic devices. This function has a high importance in industrial applications to provide a precise feeding in position controlled hydraulic drives. Today there are a limited number of methods used, all of which are cost-intensive and have specific weaknesses, such as the need for radical mechanical modifications in the cylinder structure, restricted robustness and life-time, respectively. μW technology is established in many sectors except for fac tory automation. In this study we describe an initial minimally invasive and contactless implementation of this technology for hydraulic devices. It is suitable for large piston stroke ranges in rugged environments. The degree of novelty consists of the application-specific de terminations and totally new sensing concepts. Finally original solutions, designs and test results are presented.