A Novel Capacitive Detection Principle for Coriolis Mass Flow SensorsEnabling Range/Sensitivity Tuning

We report on a novel capacitive detection principle for Coriolis mass flow sensors which allows for one order of magnitude increased sensitivity. The detection principle consists of two pairs of comb-structures: one pair produces two signals with a phase shift directly dependent on the mass flow, the other pair is used to cancel the actuation signal. This results in larger phase shifts for the same mass flows. The range and sensitivity of the sensor can be tuned by changing the amount of cancellation of the actuation frequency, e.g. the size ratio between the comb-pairs. Background A Coriolis mass flow sensor consist of a vibrating tube. Therefore, a fluid flowing inside the tube is subject to Coriolis forces, which actuates a different mode shape with an amplitude dependent on the mass flow. This transduction principle is independent of pressure, flow profile or temperature [1]. Figure 1a illustrates the twist mode (due to actuation) and the swing mode (due to the Coriolis force).