Piezoelectric crystalline materials are characterized by the ability to convert mechanical motion into electric charge changes and vise-versa. Such characteristics allow a piezoelectric crystalline material to be used as a transducer to convert mechanical strain/stress (e.g., due to pressure) and/or temperature into changes in the modulation of the material's natural mechanical oscillation frequency. Depending on the angle of the cut of the crystal lattice of a piezoelectric crystalline material from a bulk of the piezoelectric crystalline material, the resulting crystal can transform mechanical force, electrical impedance or temperature to stable changes in the oscillation frequency.
Once the crystal's transfer function is characterized against any of a desired parameter such as pressure and/or temperature, the crystal can make an adequate transducer that oscillates at a frequency reflective of the parameter. Common oscillation frequencies of piezoelectric crystals, for this application, are typically in the band from 1-5 MHz on the basis of generally available crystal sizes and cut. Determining the oscillation frequency of a piezoelectric crystal more accurately provides the ability to more precisely determine a parameter (e.g., a temperature or pressure) effecting the oscillation frequency of the piezoelectric crystal. Thus, reliable means of determining the oscillation frequency of a piezoelectric crystal that is used in the measurement of parameters such as temperature and/or pressure in an oil well is desirable.