Smart sensor system for constant dosing with micro diaphragm pumps

Abstract:
Due to cost reasons and competitiveness, downsizing technologies for independently working systems is a continuous requirement, causing a trend from conventional dosing to micro dosing. Those micro dosing systems need to provide constant and accurate dosing of gases as well as liquids, with difficulties appearing especially in medical and industrial environments by influences such as temperature, humidity and atmospheric pressure. For micro dosing systems MeMS components are used as actuators and sensors to achieve flow rates in a range between nanolitres and millilitres per minute. The type of actuators addressed in this paper are piezoelectric driven micro diaphragm pumps with passive check valves. The pulsatile flow of a diaphragm pump challenges common flow meter, due to flowrates and required accuracy. In this paper, a sensor principle that uses the pressure drop along a flow resistor is presented. The sensor system provides a flow prediction for gases with an accuracy less than 1% from the maximum measure range of 20 ml/min. The calculated flowrate is compensated for a temperature range from -20deg C to 80deg C.