Flow meter comprising a measuring insert which is insertable into a casing

A flow meter for one of a liquid and a gaseous medium (3), the flow meter comprising a casing (2;

• 24) and a measuring insert (5;
• 25) which is insertable into said casing (2;
• 24), wherein the measuring insert (5;
• 25) as a structural unit includes at least
• a) one first sound transducer (13) for emitting a first sound signal (15) into a measuring path (8) through which the medium (3) flows during operation and a second sound transducer (14) for receiving the first sound signal (15) after passing through the measuring path (8);
• and
• b) the measuring path (8) through which the medium (3) flows during operation when the measuring insert (5;
• 25) is inserted, wherein
• c) the measuring path (8) has an actual measuring channel (7) comprising a measuring channel inlet opening (7a) for the medium (3), a measuring channel outlet opening (7b) for the medium (3), and at least one measuring channel wall (9, 10, 11), wherein the measuring channel wall (9, 10, 11) at least partly surrounds the measuring path (8) in the direction of flow (4), and the casing (2;
• 24) has a casing wall (27), and a constriction (29) is provided in an intermediate region (28) between the measuring channel wall (9, 10, 11) and the casing wall (27) when the measuring insert (5;
• 25) is inserted, wherein
• d) a remaining opening (31) is provided between the measuring channel wall (9, 10, 11) and the casing wall (27) in the region of the constriction (29).