Double piston rod

摘要

A distance measuring apparatus for detecting the position of a reflection body in a line structure is provided that includes a sensor device, which has at least one antenna for feeding a transmission signal as an electromagnetic wave into the line structure and for receiving the electromagnetic wave reflected on the reflection body. The sensor device also includes evaluation electronics which are configured to determine the position of the reflection body from the phase difference between the transmitted and the received wave.

主权项

1. A cylinder having a distance measuring apparatus, comprising:
a cylinder casing; a coaxial system including first and second coaxial piston rods, the first piston rod being located inside the second piston rod, the first piston rod having a first reflective surface, the second piston rod having a second reflective surface; at least one antenna for feeding transmitted electromagnetic waves into the cylinder and for receiving electromagnetic waves reflected off of the first and second reflective surfaces, at least one of the antennas being a capacitive means or a coupling slot; evaluation electronics coupled to the at least one antenna and being configured to determine the position of the reflective surfaces from the phase differences between the transmitted waves and the waves reflected off of the first and second reflective surfaces; and a short circuit for the electromagnetic wave located on the first or second reflective surface, the short circuit comprising two or more metallic discs having a dielectric finer there between.