Apparatus for determining the flow rate of a flowing medium

摘要

An apparatus for determining the flow rate of a flowing medium having a substrate as a carrier and a resistor arrangement disposed on the substrate which among other elements includes a layer-like measuring resistor (RH) as well as a likewise layer-like heating resistor (RS), the heating output of which is regulated such that the measuring resistor (RH) has a constant temperature, the heating output of the heating resistor (RS) being a standard for the flow rate of the flowing medium. The surface area of (RS) is greater than the surface area of (RH) and extends farther toward a fastening of the substrate, in order to prevent a flow of heat out of the vicinity of the measuring resistor (RH). The measuring resistor (RH) and the heating resistor (RS) are located on the downstream portion of the substrate, on a lip set off by a slit. With this disposition of the measuring resistor (RH), soiling of the substrate affects the measurement result only slightly.