Research on accuracy enhancement of pressure sensors based on stress-isolation packaging

For high-precision resonant pressure sensors, the resonant frequency of the sensing element typically ranges from 20 kHz to 40 kHz. Minor fluctuations in this frequency can significantly affect pressure measurement accuracy, while temperature coupling further complicates the output, necessitating effective calibration. To enhance frequency accuracy and output stability over the full temperature range of −55 ℃ to 100 ℃, this paper proposes a miniaturized sensing element integrated with a multi-layer stress isolation structure, which effectively mitigates stress transmission induced by temperature variations. Building upon the conventional self-oscillating circuit for resonant pressure sensors, the C2V circuit is optimized to improve the signal-to-noise ratio at the detection end, thereby ensuring stable sensor operation. A frequency extraction algorithm based on square wave cycle counting is developed in conjunction with microcontroller unit (MCU) interrupt timing control to improve frequency resolution. Moreover, an online three-dimensional multi-order calibration model is established for pressure output to enable comprehensive accuracy evaluation. Experimental results demonstrate that the silicon resonant structure encapsulated with the multi-layer stress isolation structure achieves a reduction in both size and weight of more than 80% compared to a metal-packaged counterpart. The proposed closed-loop control circuit enables stable high-frequency oscillation and square wave generation. Over the temperature range of −55 ℃ to 100 ℃ and the pressure range of 3.5 kPa to 110 kPa, the maximum frequency output deviation is less than 0.14 Hz, with a stability of 0.02 Hz (RMS). The pressure output deviates from the reference value by less than 17 Pa, corresponding to a pressure measurement accuracy of 0.0154%.