Abstract: In accordance with one embodiment of the invention, a method and system for detecting the position of a shaft comprises providing a shaft with defined hardened metallic regions. The shaft has a first hardened metallic region from a surface of the shaft to a first radial depth from the surface at a first longitudinal position. The shaft has a second hardened metallic region from the surface of the shaft to a second radial depth at a second longitudinal position. The second radial depth is different from the first radial depth. A sensor senses an eddy current to detect an alignment of at least one of the first hardened metallic region and the second hardened metallic region with a fixed sensing region at a respective time. A data processor determines a longitudinal position of the shaft with respect to a cylinder at the respective time based on the sensed eddy current.

Abstract: A cylinder position sensing system includes a cylinder housing which slidably receives a rod or shaft element. The cylinder housing has an end piece which slidably receives the shaft element. A first axial groove is formed in the shaft element, and a first magnet member is mounted in the first groove. A second helical groove is formed in the shaft element and is spaced apart from the first groove. A second magnet member is mounted in the second groove. A magnetic field sensor is mounted in the cylinder housing so that the sensor generates an output signal as a function of a relative distance between the first and second magnet members as the second element moves with respect to the first element. Preferably, the shaft element includes a central cylindrical shaft and a hollow cylindrical sleeve mounted over and receiving the shaft. Preferably, the first and second grooves are formed in an inner surface of the sleeve, and the sleeve and the end piece are formed of nonferrous material.

Abstract: A cylinder position sensing system includes a cylinder housing which slidably receives a rod or shaft element. The cylinder housing has an end piece which slidably receives the shaft element. A first axial groove is formed in the shaft element, and a first magnet member is mounted in the first groove. A second helical groove is formed in the shaft element and is spaced apart from the first groove. A second magnet member is mounted in the second groove. A magnetic field sensor is mounted in the cylinder housing so that the sensor generates an output signal as a function of a relative distance between the first and second magnet members as the second element moves with respect to the first element. Preferably, the shaft element includes a central cylindrical shaft and a hollow cylindrical sleeve mounted over and receiving the shaft. Preferably, the first and second grooves are formed in an inner surface of the sleeve, and the sleeve and the end piece are formed of nonferrous material.