Stabilized-load crystal oscillator

Abstract

The presence and concentration of some gases can be sensed by quartz crystal resonators covered by a thin layer of gas-absorbing material. The absorbed gas increases the inertial mass of the layer, and as a result the resonating frequency of the crystal is changed. However, a disadvantage of this method lies in the fact that the absorbed mass increases internal friction in the sensing layer, leading to increased damping, in other words dropping the Q-factor of the resonator. If the resonating frequency is to be measured by using the resonator as the frequency-determining device of an autonomous oscillator, accuracy problems appear due to the wide variations of the resonator Q-factor. The following article shows effective patented methods diminishing this problem.