Physical Property
Changes in the electrical resistivity of a semiconductor or metal occur when the material is subjected to mechanical strain. This piezoresistance effect forms the basis for most modern pressure sensors and strain gauges. It differs from the piezoelectric effect through its reliance on resistance change to indicate strain.
Semiconductor Mechanism
Crystal lattice deformation in silicon alters the mobility and density of charge carriers within the energy bands. The piezoresistance in doped silicon is substantially higher than that found in metallic alloys. This sensitivity is utilized by diffusing resistors into a silicon diaphragm.
When the diaphragm flexes under pressure, the resulting strain produces a measurable change in the resistance of the bridge circuit.
Measurement Integration
Bridge circuits, typically in a Wheatstone configuration, convert the resistance shift into a proportional voltage output. While the piezoresistance provides a high signal to noise ratio, it also exhibits a strong dependency on temperature. Modern sensor designs include compensation resistors or digital correction algorithms to counteract this thermal sensitivity.
These systems ensure that the output remains linear across the entire operating pressure range of the device.
Application Scope
Microsensors for automotive and industrial monitoring rely on this principle for their high reliability and small footprint. The stability of piezoresistance makes it suitable for long term monitoring of hydraulic systems and gas pressures.
