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A Dual-Resonator Temperature Sensing Approach With Time Base Error Suppression

In this study we present a novel dual-resonator temperature sensor which can be embedded in other MEMS sensors for improved thermal compensation and on-the-run calibration. For accurate temperature measurements, the proposed method mitigates time base errors in frequency counting, eliminates the need for a highly accurate reference clock and can cancel out the effects of aging of the time base without using a calibration process. The sensor structure is composed of a strain amplifying beam and two Double Ended Tuning Fork (DETF) resonators with different temperature sensitivities. The DETFs are kept at resonance simultaneously with a dual PLL circuit. Experiments reveal that at the expense of decreasing sensitivity, one can suppress the measurement errors which can be as high as 0.164 degrees C for the long resonator and 0.240 degrees C for the short resonator when a time base of 50 ppm accuracy is used. Moreover, while the frequency stability characteristics of the single sensing elements deteriorate drastically as the accuracy of the time base decreases, the frequency stability of the proposed frequency ratio remains unaffected and it is superior compared to both of the resonators.