Experimental analysis of thermomechanical noise in micro Coriolis mass flow sensors

Coriolis mass flow sensors mechanically detect mass flows using a vibrating channel. For microfabricated sensors, thermomechanical noise causes random vibrations and defines therefore a fundamental limit to the resolution of the sensor. This is modeled using the equipartition theorem. In an experimental setup, the displacement of the channel due to thermomechanical noise is measured using a laser Doppler vibrometer for temperatures between approximately 300 K and 700 K. The results show RMS vibration amplitudes of 38 pm to 57 pm for a bandwidth of 13 Hz, as predicted by the model. This corresponds to a noise equivalent mass flow of 0.3 ng/s. It is shown that the resolution of the currently most sensitive Coriolis mass sensor is still one to two orders of magnitude above the thermal noise limit.