A novel flow sensor with high time resolution based on differential pressure principle

In this paper, a novel flow sensor for liquids is presented. This concept allows a simple one-chip solution based on an established technology. The sensor consists of a common piezoresistive pressure sensor with an orifice in the sensor diaphragm, which forms a flow restriction. If the diameter of the orifice is made large compared to the thickness of the pressure sensor membrane, the flow signal becomes temperature-independent. Experiments have shown, that the time resolution of the sensor is in the order of one millisecond. Further, gas bubbles cause a blocking effect the threshold pressure of which varies between a few hPa at large orifices and about hundred hPa at small orifices.