In the world of high-precision pressure measurement, monocrystalline silicon and diffused silicon represent two different generations of piezoresistive technology.

While both rely on the piezoresistive effect—where the electrical resistance of a material changes under mechanical stress—they differ significantly in how the sensing element is constructed and how it performs in industrial environments.

Comparison Matrix

1. Diffused Silicon Sensors (The Industrial Workhorse)

These are the most common sensors in the general industry. They are typically made by diffusing P-type impurities (like Boron) into an N-type silicon substrate to form a Wheatstone bridge.

• Structure: The sensing chip is usually protected by a stainless steel diaphragm and filled with silicone oil to transmit pressure.
• Pros: Very fast dynamic response and excellent price-to-performance ratio for standard hydraulics and oil/gas pipelines.
• Cons: They are highly sensitive to temperature. Without sophisticated external compensation circuits, the “zero point” (the reading at zero pressure) can drift significantly as the ambient temperature changes.

2. Mono-crystalline Silicon Sensors (The Precision Standard)

These represent an “upgraded” version of piezoresistive technology, often utilising MEMS (Micro-Electro-Mechanical Systems) technology and a “double-beam suspension” design.

• Structure: The core is a single, continuous crystal of silicon. Because the lattice is perfectly uniform, electron mobility is much higher and more predictable than in diffused silicon.
• Pros: Anti-Overload: Many designs use a “suspended” chip that isn’t directly crushed by pressure, allowing them to survive massive pressure spikes that would burst a standard diffused sensor.
• Hysteresis: The “memory” effect of the material is almost zero; the sensor returns to exactly the same value every time pressure is released.
• Cons: Higher manufacturing complexity leads to a significantly higher price tag.

Key Technical Distinction: “Creep” and “Hysteresis”

The primary reason engineers choose Mono-crystalline over Diffused is Elasticity.

• Diffused silicon behaves like a high-quality spring that might slightly lose its shape after being stretched a million times.
• Mono-crystalline silicon is closer to a “perfect” elastic body. This means its 5-year stability is often rated at 0.1%, whereas a diffused sensor might drift by 0.5% or more in the same period, requiring more frequent calibration.

Summary: Which one do you need?

• Use Diffused Silicon if: You are building a standard hydraulic system, water pump, or general industrial machinery where “good enough” accuracy (0.25%) is acceptable, and budget is a major factor.
• Use Mono-crystalline Silicon if: You are working in Process Automation (like a refinery or power plant), dealing with Differential Pressure (DP) flow measurement, or in any scenario where recalibrating the sensor is difficult or expensive.

Rocksensor offers a Monocrystalline Silicon Piezoresistive Sensor with its RP1000 Series Transmitters.