Silicon resonant pressure sensors stand out in the field of high-precision measurement due to their unique principle of pressure-frequency conversion and the characteristics of silicon-based materials. However, compared with other types of sensors (such as piezoresistive, capacitive, piezoelectric, vibrating wire, etc.), their advantages stem from the differences in technical principles and structural designs. The specific comparisons are as follows:
1.Precision Advantages at the Principle Level
٭ Pressure-frequency conversion with inherent noise resistance: Directly output digital signals (frequency quantities) through the frequency changes of the silicon resonant structure, avoiding the analog-to-digital conversion errors, signal amplification noise, and long-wire transmission losses of traditional piezoresistive (voltage signals) or capacitive (capacitance changes) sensors. The frequency signal has extremely strong electromagnetic interference resistance (such as resistance to radio frequency interference of 100V/m), and the accuracy can reach 0.01%FS (while piezoresistive sensors typically have an accuracy of 0.1%FS to 0.5%FS).
٭ Excellent linearity and repeatability: The stress-frequency response linearity of the silicon resonant structure is greater than 0.9999, and the nonlinear error is less than 0.01%FS, far superior to capacitive sensors (with a nonlinear error of approximately 0.1%FS) and piezoresistive sensors (which require post-calibration to correct nonlinearity).
2.Material and Structural Stability
٭ Temperature characteristics of silicon-based materials: The coefficient of thermal expansion of silicon is extremely low (2.6×10⁻⁶/℃), and the elastic modulus changes little with temperature (the change within the range of -50℃ to +125℃ is less than 5%). With the design of symmetrical dual resonators (temperature differential compensation), the temperature sensitivity can be reduced to 1×10⁻⁶/℃, enabling high-precision compensation without the need for additional temperature sensors (the temperature drift of piezoresistive sensors is usually greater than 100×10⁻⁶/℃).
٭ Solid-state with no moving parts: The integrated resonant beam/diaphragm structure manufactured by MEMS technology has no problems of mechanical contact or aging of seals. The annual drift rate is less than 0.01%FS (the annual drift of vibrating wire sensors is about 0.05%FS, and that of capacitive sensors is even higher), making it suitable for long-term stable monitoring (for example, the aviation atmospheric data system needs to operate reliably for decades).
3.Digital Output and Intelligent Characteristics
٭ Direct digital signal output: The frequency signal can be directly collected by the microprocessor without the need for complex signal conditioning circuits, simplifying the system design and reducing the risk of noise introduction (in contrast, piezoresistive sensors require adaptation to ADC circuits and are vulnerable to power supply noise).
٭ On-chip self-calibration capability: The built-in MCU or ASIC can achieve power-on self-check and periodic self-calibration (such as comparing with the quartz reference frequency), automatically correcting long-term drift without the need for manual calibration (traditional sensors require regular offline calibration).
4.Dynamic Response and Resolution
٭ High Q value and high resolution: Vacuum packaging (atmospheric pressure < 10⁻³Pa) gives the resonator a quality factor Q > 10,000, and the pressure resolution can reach 0.001hPa (0.1Pa), which is suitable for measuring small pressure changes (such as detecting the vertical height of the atmosphere), far surpassing piezoresistive sensors (with a resolution of about 1hPa) and capacitive sensors (with a resolution of about 0.1hPa).
٭ Wide dynamic range: Through structural design, it can cover the range from micro-pressure (0~1kPa) to medium-high pressure (0~10MPa), and maintain high precision within the full range (for traditional sensors, the wider the range, the more obvious the decrease in accuracy).
The core advantages of silicon resonant pressure sensors lie in "high precision, high stability, and digital characteristics". Technically, the essence is to convert the pressure measurement error from "errors in the multi-link analog signal chain" into "errors in single frequency measurement" through the "silicon-based resonant structure + pressure-frequency conversion", and achieve error suppression through the optimization of the full link of materials, structures, and algorithms.