Patent ID: 6915689
Filing Date: 2005-07-12
Classification: H01Q

Abstract:
1. An apparatus for high accuracy gauging of the level of a liquid in a container, above which level there exists a gas having a dielectric constant within a predetermined dielectric constant range, comprising: a transmitter for transmitting a microwave signal in a first mode of propagation in a tube through said gas towards the surface of said liquid, wherein the walls of said tube is provided with a number of holes so that the liquid in said container can flow laterally in and out of said tube to maintain a unitary level of said liquid inside and outside said tube; a receiver for receiving the microwave signal reflected against the surface of said liquid and propagating back through said tube; and a signal processing device for calculating from the propagation time of the transmitted and reflected microwave signal the level of said liquid in said container, wherein said transmitter is adapted to transmit said microwave signal in a frequency band, at which the group velocity of a microwave signal in said first mode of propagation in said tube is, within said predetermined dielectric constant range, essentially independent of the dielectric constant.