Diffused Silicon Pressure Sensor: Working Principle, Advantages, Disadvantages, Features, Applications & Summary
1. Working Principle
The diffused silicon pressure sensor operates on the piezoresistive effect — the phenomenon where the resistivity of semiconductor materials changes under mechanical stress. A set of equal-value resistors are formed on a monocrystalline silicon diaphragm through diffusion technology and connected as a Wheatstone bridge.
When pressure is applied to the silicon diaphragm, it produces a slight deformation (normal displacement less than 0.025 mm), causing the resistance values to change. The bridge outputs a weak voltage signal proportional to the pressure, which is amplified and converted into a standard industrial signal.
2. Advantages
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High accuracy — Comprehensive accuracy up to ±0.5%FS, with high-precision models reaching ±0.1%FS.
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High sensitivity — Full-scale output of approximately 100mV, significantly higher than traditional strain gauge sensors (approx. 10mV).
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Compact and lightweight — Small footprint, easy to integrate and install.
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Good long-term stability — Better than ±0.2%FS per year.
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Cost-effective — Mature technology and low cost, making it the "workhorse" of industrial automation.
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Intrinsically safe — Low voltage and low power consumption, suitable for hazardous locations.
3. Disadvantages
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Temperature drift — Stability degrades below 0°C and above 85°C.
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Not suitable for high pressure — Typically not suitable above 20MPa.
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Fragile diaphragm — Thin silicon diaphragm is susceptible to mechanical shock.
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Requires additional protection — Otherwise prone to moisture damage.
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Not suitable for dynamic pressure — Cannot handle rapidly fluctuating pressures.
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Zero drift — Requires periodic calibration (recommended annually).
4. Key Features
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Based on piezoresistive effect, no moving parts — fast response, high reliability.
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Semiconductor diffusion technology — monolithic integration of diaphragm and resistors.
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Standard analog signal outputs (4-20mA, 0-5V, etc.).
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Laser trimming and wide temperature compensation.
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Optional all-stainless steel construction for corrosion resistance.
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Available in gauge, differential, and absolute pressure types.
5. Applications
| Industry | Applications |
|---|---|
| Oil & Chemical | Reactor and pipeline pressure measurement |
| Power Generation | Steam pressure and boiler water level monitoring |
| Metallurgy | Furnace top pressure and cooling water monitoring |
| Pharmaceutical | Reactor pressure control and vacuum measurement |
| Food & Beverage | Filling line and fermentation tank pressure control |
| Water Treatment | Pump control, level measurement, pipeline monitoring |
| Automotive | Engine oil pressure and brake system monitoring |
| HVAC | Refrigeration, compressor, and hydraulic pressure control |
6. Summary
The diffused silicon pressure sensor is a high-precision, cost-effective device widely used in industrial automation. Its key strengths are high accuracy, compact size, good stability, and easy integration. Its main limitations are temperature drift, unsuitability for high pressure, and a fragile diaphragm. It remains an essential component across petrochemical, power, pharmaceutical, and automotive industries.
