Ultrasonic flow sensor for use in a fluid medium

An ultrasonic flow sensor for use in a fluid medium, comprising:

• at least two ultrasonic converters, which are situated in a flow tube offset relative to one another, longitudinally with respect to a flow of the fluid medium;
• a reflection surface, wherein the at least two ultrasonic converters are set up to exchange ultrasonic signals via simple reflection on the reflection surface;
• and
• a deflection device disposed between the ultrasonic converters along an axis connecting the ultrasonic converters, wherein the deflection device is set up to suppress at least 30% of parasitic ultrasonic signals, which are reflected from the reflection surface and which strike the deflection device, by deflection away from the ultrasonic converters;
• and wherein the deflection device has at least one deflection surface having a substructuring oriented to reflect ultrasonic signals, the substructuring having one or more of the following structures:
• multiple ribs;
• multiple grooves;
• a grid;
• a substructuring having multiple surfaces;
• a substructuring having multiple ones of the structures.