Capacitive sensor for a fluid forming a dielectric in a capacitor

Abstract

A capacitive sensor for measuring a characteristic of a fluid or a filling depth of a liquid in a container is constructed of a printed circuit board that is either flexible or has stiff and flexible sections along its length. Metal coatings forming capacitor plates are formed, for example by printed circuit techniques on one or both sides of the circuit board which is then bent into such a configuration that two capacitor plates forming a capacitor face each other across a spacing that is accurately maintained by spacers. The bent shape of the circuit board has, for example, a U-configuration, an inverted S-configuration, or an e-configuration. Additional metal coatings are provided for screening purposes against adverse field influences. Conductor leads are provided on the printed circuit board for connecting the capacitor plates to an evaluating circuit, and the metal screens to a reference potential such as ground. The bent circuit board is held in position in a frame that itself may form a housing provided with openings for the inflow and outflow of the fluid which forms a dielectric between the capacitor forming plates. Lateral and vertical movement of the bent circuit board is further restrained by position fixing pins.

Dependencies are inferred from the claim text.