Improved capacitive detection method for Coriolis mass flow sensors enabling range/sensitivity tuning

Abstract

We report on a novel capacitive detection principle for Coriolis mass flow sensors which allows for three times increased sensitivity. Capacitive Coriolis mass flow sensors are normally read out by two electrodes that measure the ratio between the actuation mode and the Coriolis mode, which is induced by the mass flow. This ratio results in a phase shift between the two electrodes. By adding two additional read out electrodes, the actuation mode signal is partially cancelled, allowing for higher sensitivity to the Coriolis mode, and thus larger phase shifts for the same mass flows. An analytical model is derived and correspond with the measurements. It is also proven that the range and sensitivity of the sensor can be tuned by changing the size of the additional readout electrodes. This readout method does not increase the readout time.

Towards nanogram per second Coriolis mass flow sensing

“…imperfections in the fabrication process). Using combs very close to the twist axis in combination with the actuation amplitude cancellation presented by Alveringh et al [9] can further increase the sensitivity to mass flow.…”

Experimental analysis of thermomechanical noise in micro Coriolis mass flow sensors

“…Hence, this sensor is still limited by noise in the readout circuitry and an improvement by a factor of 50 is possible. Improved methods for capacitive readout of Coriolis mass flow sensors have been published recently [24].…”

Integrated Pressure Sensing Using Capacitive Coriolis Mass Flow Sensors

“…The ratio between the two modes can be measured using two capacitive readout structures which produce the signals C 1 (t, P) and C 2 (t, P) as illustrated in Figure 10. The phase shift φ is related to this ratio, and thus, to mass flow [16]:…”