Fill level gauge

Abstract

A fill level gauge operating by the radar principle and preferably used for measuring the fill level of a liquid or fluid in a container incorporates a microwave generator for generating a microwave signal, a waveguide for conducting the microwave signal, a horn radiator serving as a transmitting and/or receiving antenna, an impedance transformer, and a connecting flange, where the horn radiator is positioned on the near side of the connecting flange facing the liquid and the impedance transformer extends at least partially into the opening of the horn radiator. An obturator plate is designed as an integral extension of the impedance transformer and is positioned between the horn radiator and the connecting flange. This design permits easy replacement of the impedance transformer while providing a secure seal at the junction between the horn radiator and the impedance transformer.

I claim:  
     
         1 . A fill level gauge, operating by the radar principle and preferably used for measuring the fill level of a liquid or fluid in a container, incorporating a microwave generator for generating a microwave signal, a waveguide for conducting the microwave signal, a horn radiator serving as a transmitting and/or receiving antenna, an impedance transformer, and a connecting flange, where the horn radiator is positioned on the near side of the connecting flange facing the liquid and the impedance transformer extends at least partially into the opening of the horn radiator, wherein an obturator plate is provided which is positioned between the horn radiator and the connecting flange and which is an integral extension of the impedance transformer.  
     
     
         2 . The fill level gauge as in  claim 1 , wherein the obturator plate covers the entire contact surface of the horn radiator.  
     
     
         3 . The fill level gauge as in  claim 1  or  2 , wherein the obturator plate and the impedance transformer consist of a chemically resistant plastic material.  
     
     
         4 . The fill level gauge as in  claim 1  or  2  wherein, on its side opposite the impedance transformer, the obturator plate is provided with a waveguide insert which is an integral part of the obturator plate and by way of which the microwave signal can be coupled into the impedance transformer.  
     
     
         5 . The fill level gauge as in  claim 4 , wherein the waveguide insert consists of a chemically resistant plastic material.  
     
     
         6 . The fill level gauge as in  claim 1  or  2 , wherein the entire surface of the horn radiator that is in contact with the inside of the container is coated with a dielectric.  
     
     
         7 . The fill level gauge as in  claim 6 , wherein the maximum thickness of the dielectric layer is 2 mm.  
     
     
         8 . The fill level gauge as in  claim 6 , wherein the dielectric is a ceramic material.  
     
     
         9 . The fill level gauge as in  claim 6 , wherein the dielectric is a plastic material selected from the group consisting of PTFE, PFA, FEP and PVDF.  
     
     
         10 . The fill level gauge as in  claim 6 , wherein the dielectric is an enamel.  
     
     
         11 . The fill level gauge as in  claim 10 , wherein an eyelet created in the process of coating the horn radiator with enamel serves as a contact for grounding the horn radiator.