フルディジタル位相検出型QCM

抄録

In this paper, we propose a new method to improve the frequency resolution and time resolution of QCM, which measures masses of several nanograms or less by using changes in the resonance frequency of the quartz crystal resonator. Since our method does not use a frequency counter to measure the frequency, there is no waiting time due to the gate time, therefore high-speed frequency measurement is possible. In this method, the output waveforms of two crystal oscillators are sampled directly by a 2-channel AD converter and the phase is calculated by numerical calculation processing on the sampled digital data. The instantaneous frequency is calculated from the time derivative of the obtained phase and converted into the change in mass.

In order to verify the frequency measurement accuracy of the fully digital phase detection QCM, the frequency change simulating the mass change was used and compared with the conventional high-precision differential QCM using reciprocal counter. As a result, it was shown that the frequency resolution and time resolution could be significantly improved.