Device for transmission measurement with the aid of microwaves

A system for transmission measurement with the aid of microwaves for the continuous determination of the concentration of a substance, said system comprising:

• two waveguides having measuring portions which are immersed into the substance, said two waveguides comprising a transmission waveguide antenna for radiating microwave energy and a receiving waveguide antenna for receiving radiated microwave energy, each of said waveguides being provided with a window that is transparent to microwave radiation;
• and a signal processing circuit connected to said waveguides for supplying a microwave signal to said transmission waveguide antenna to cause said transmission waveguide antenna to radiate microwave energy via said window of said transmission waveguide antenna and for receiving from said receiving waveguide antenna a microwave signal created in said receiving waveguide antenna by microwave radiation received by said receiving waveguide antenna through said window in said receiving waveguide antenna.