Micro Coriolis Mass Flow Sensor with Integrated Capacitive Readout

Abstract

We have realized a micromachined micro Coriolis mass flow sensor with integrated capacitive readout to detect the extremely small Coriolis vibration of the sensor tube. A special comb-like detection electrode design eliminates the need for multiple metal layers and sacrificial layer etching methods. Using differential readout signals significantly reduces the influence of parasitic capacitances. In addition, the sensing electrodes have been realized on a suspended tube structure which will allow for tuning of the electrode separation by a DC current. First measurements using water, ethanol and white gas indicate that true mass flow is measured by the sensor and that sensor output is linear with mass flow. The measurement error is currently in the order of 2% of the full scale of 1.2 ml/hr for all measured liquids (which corresponds to 1.2 g/hr in the case of water).