A cassette module (19, 29, 319, 419, 59, 69) for a differential flowmeter is disclosed, wherein the cassette module (19, 29, 319, 419, 59, 69) forms a first fluid-carrying channel (16, 216, 316, 611, 615) and the second fluid-carrying channel (17, 217, 317, 610, 616) during operation of the differential flowmeter. The cassette module is specific in the regard that a geometric deformation of the channels due to a temperature difference between the channels (16, 216, 316, 611, 615, 17, 217, 317, 610, 616) is minimized or prevented. In addition a differential flowmeter containing the cassette module (19, 29, 319, 419, 59, 69) disclosed here is also described.
