Conventional differential pressure sensors detect the deformation of a thin membrane under pressure, using piezoresistive or capacitive methods. For a measurement range below 3kPa these sensors are imprecise and their fabrication is relatively difficult. The use of thermal flow sensors is a good alternative to measure such small pressure difference. In order to measure pressure difference with a flow sensor, the two regions with different pressure values are connected to each other with a small, defined flow channel. A flow occurs, which depends on the pressure difference and which is measured with a thermal flow sensor. The resulting flow signal is proportional to the pressure difference.