Solid State Transduction
Solid-state transducers utilize the change in electrical resistivity of a semiconductor when subjected to mechanical stress to measure pressure or force. A silicon piezoresistive sensor consists of a thin diaphragm with integrated resistive elements. It offers high sensitivity and a small form factor compared to mechanical gauges.
The device is manufactured using the same lithographic processes as computer chips.
Lattice Distortion
Applying pressure to the sensor bends the silicon and shifts the position of the atoms. In a silicon piezoresistive sensor, this distortion changes the band structure of the material and affects the flow of electrons. This is a reversible process that occurs at the speed of sound in the crystal.
Bridge Configuration
Four resistors are typically arranged in a loop to detect small changes in resistance. The silicon piezoresistive sensor uses this configuration to cancel out common errors like temperature-induced drift. A constant voltage or current is applied to the bridge to generate an output signal.
Sensitivity Factor
The magnitude of the resistance change per unit of stress is known as the gauge factor. Because a silicon piezoresistive sensor has a gauge factor nearly one hundred times larger than metal, it can detect very small pressure changes. This sensitivity makes it ideal for medical and industrial applications.
