A 6MHz QCM Sensor with a Miller XCO and its application in liquid media

A 6 MHz quartz crystal microbalance (QCM) sensor with a Miller oscillator is proposed for liquid media. It can solve the working in damping media problems of standard crystal controlled oscillators (XCO). The design is adapted to the conditions of strong damping that the quartz experiences, so that the oscillation stays in spite of the reduction of the resonator quality factor. The characteristic polynomial method is employed to optimize the design. The conditions to obtain a stable frequency according to the resonator damping and the static capacity are studied. In conclusion, the sensor has such advantages as: 1) Low noise because of based on a high stability classical oscillator 2) Appropriated for electrochemical applications because of one metallic electrode of the resonator is grounded. 3) Good capacity to work under strong damping. 4) High sensitivity and resolution because the frequency change per unit of measurand and the smallest frequency deviation that can be detected in presence of noise are higher