Resonant sensors have many advantages such as high sensitivity, long term stability and easy interfacing with digital
signal processing. In this paper, we design and realize a resonant mass sensor. In order to get resonator of high Q value,
tapered and thin oscillating tube is designed as the oscillator. Self-excited oscillation mode and closed-loop driving
circuit is used, which enables the oscillating frequency stabilize in the natural frequency of the oscillator. Meanwhile,
automatic gain control circuit is designed to keep constant amplitude of oscillating. Finally, this mass sensor achieve
successful in measurement of concentration of aerosol. The experimental results show that the mass sensor takes
advantages of compact structure, high precision and high reliability.