Quartz crystal is one kind of piezoelectric material in specific orientation. Electric field is applied to both side of quartz blank to induce the mechanic and electrical coupling. When electric field is applied to quartz blank, the electric field will induce the mechanical deformation, which also will generate an reverse electrical potential. The interaction between mechanical deformation and electrical potential cause a continuous vibration. This mechanical and electrical interaction coupling effect is called piezoelectric effect.
Different sharp or thickness of quartz blank in various vibration modes decides the frequency of the continuous vibration. In the most common usage of AT vibration mode, the vibration frequency is reverse proportional to the thickness of the blank.
Generally, we call quartz blank mechanical vibration in minimum impedance as resonance oscillation that can be instated in effective LC oscillation circuit. There are two kinds of effective oscillation circuit in application side. One is RLC series oscillation; another is RLC and C0 parallel oscillation. According to the impedance versus oscillation frequency curve, oscillation in Fr frequency gets the minimum impedance and oscillation in Fp frequency gets the maximum impedance.