Mass load effect of quartz crystal is a part of the measurement principle. Quartz crystal vibrates when imputing electrical oscillation. The QCM sensor vibrates in thick shear mode at a max. frequency of 30 Mhz. When a substance is adsorbed onto the electrode of the QCM sensor, the frequency shifts to the lower side equivalent for mass amount. This characteristic is called as “Mass load effect.” The example diagram here shows the frequency shift.