Resonator self-temperature-sensing using a dual-harmonic-mode crystal oscillator

A thermometry method using resonator self-temperature-sensing is described. The method uses a harmonically related pair of c-modes of an SC-cut that is simultaneously excited in a dual-mode oscillator, and then combined to produce a thermometric frequency having a monotonic and nearly linear dependence on temperature. It avoids the activity dip problems of the b-mode and overcomes limitations of using external sensors that are subject to thermal lab and temperature gradients. This method provides a means of measuring resonator temperature with high accuracy, limited only by the stability difference between the c-mode frequencies. The concept for this dual c-mode thermometry method is presented and its implementation in a microcomputer-compensated crystal oscillator discussed