Detection Principles of Temperature Compensated Oscillators with Reactance Influence on Piezoelectric Resonator This review presents various ways of detection of different physical quantities based on the frequency change of oscillators using piezoelectric crystals. These are influenced by the reactance changes modifying their electrical characteristics. Reactance in series, in parallel, or a combination of reactances can impact the electrical crystal substitute model by influencing its resonant oscillation frequency. In this way, various physical quantities near resonance can be detected with great sensitivity through a small change of capacitance or inductance. A piezoelectric crystal impedance circle and the mode of frequency changing around the resonant frequency change are shown. This review also presents the influence of reactance on the piezoelectric crystal, the way in which the capacitance lost among the crystalxe2x80x99s electrodes is compensated, and how the mode of oscillatorsxe2x80x99 output frequency is converted to lower frequency range (1xe2x80x93100 kHz). Finally, the review also explains the temperaturexe2x80x93frequency compensation of the crystalsxe2x80x99 characteristics in oscillators that use temperaturexe2x80x93frequency pair of crystals and the procedure of the compensation of crystals own temperature characteristics based on the method switching between the active and reference reactance. For the latter, the experimental results of the oscillatorxe2x80x99s output frequency stability (fout  xc2xb10.002 ppm) at dynamical change of environment temperature (0xe2x80x9350 xc2xb0C) are shown.

A FaceShear Mode Piezoelectric Array Sensor for Elasticity and Force Measurement We present the development of a 6 xc3x97 6 piezoelectric array sensor for measuring elasticity and force. The proposed sensor employs an impedance measurement technique, sensing the acoustic load impedance of a target by measuring the electrical impedance shift of faceshear mode PMNxe2x80x93PT (lead magnesium niobatexe2x80x93lead titanate) single crystal elements. Among various modes of PMNxe2x80x93PT single crystals, the faceshear mode was selected due to its especially high sensitivity to acoustic loads. To verify the elasticity sensing performance, gelatin samples with different elastic moduli were prepared and tested. For the force measurement test, different magnitudes of force were loaded to the sensing layer whose acoustic impedance was varied with applied forces. From the experimental results, the fabricated sensor showed an elastic stiffness sensitivity of 23.52 OhmMPa with a resolution of 4.25 kPa and contact force sensitivity of 19.27 OhmN with a resolution of 5.19 mN. In addition, the mapping experiment of elasticity and force using the sensor array was successfully demonstrated.