Noise and resolution in 2 MHz, 6 MHz, 9 MHz and 27 MHz QCM sensors in liquid media

In this paper, a comparative study of noise and resolution is presented with respect to the frequency and the quality factor. The study has been made using four oscillators designed to be used in quartz crystal microbalance sensors in damping media. The four circuits have been designed at increasing frequencies in order to improve the sensitivity. Also, a calibration of the sensors was made. On the other hand, the current resolution limit of a microbalance oscillator is determined using an AT resonator, since this does not depend on the frequency. However, when working in liquid, the damping of the resonator makes the resolution diminish due to a worsening the quality factor. The relationship between the resolution limit and the frequency and characteristics of the liquid medium has been determined. The resolution worsens when the density and viscosity of the liquid is increased. However, in this case, the increase in frequency implies a small increase in the resolution. Therefore, when working below the maximum quality factor, for similar values, the resolution can be improved by elevating the work frequency.