A resonant micro-cantilever frequency tracking system based on dynamic phase difference

Gravimetric system based on resonant micro-cantilever had drawn significant attention in trace material detection. Adsorption quantity could be measured by the change of cantilever´s resonant frequency, and phase-locked loop (PLL) was commonly used to keep the cantilever resonating. However, in the application of traditional PLL, we have to adjust parameters of the phase shifter to make sure the locked frequency matching with the cantilever´s resonant frequency. In this manuscript, we promoted a frequency tracking system based on software phase-locked loop. Locked phase was calculated automatically, so the system could match with cantilevers of different resonant frequency, and no adjusting is need anymore. This system could combine with instruments based on frequency tracking and detection easily, not only limited to resonant cantilevers.