Flow sensors are of great importance in automotive domains for air flow determination. A steep increase is seen also for fluid measurements with high resolution in smallest flow ranges [1, 2]. Demands are found in medical fields, chemical analytics and biotechnological analysis [3, 4]. Those fields ask for disposable low-cost products. We report on a flow sensor detecting small pressure differences (10-600 Pa) with high precision for use in air conditioning field [5]. The transducer used the fact that small pressure differences between two cavities can be detected via the pressure driven flow along a well defined fluidic resistor connecting both cavities. To measure such very low flow rates, decreasing the flow channel cross section is favorable because it leads to an increase of the fluid velocity. For very small flow channel dimensions also the fabrication tolerances have to be small to avoid large signal deviations. For low cost sensors no calibration during the production process should be necessary. So a very high device-to-device reproducibility is needed. In order to attain this aim we monolithically integrated a micro-channel acting as a well defined fluidic resistance into the sensor die (figure 1). Due to the channel integration a simplified packaging is achieved leading to low cost concepts of injection molding housing for the flow sensor.
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