Pressure sensors are widely used to monitor fluid pressure in pipes, engines, hydraulic systems, and nature. They work on the principle of piezoresistance and use film resistors, strain gauges, metal alloys, or polycrystalline semiconductors as resistive media. There are various types of pressure sensors, including absolute, gauge, and differential pressure sensors. An intermediate medium is often used to prevent damage to the sensitive sensing device when measuring volatile or corrosive materials.
Pressure sensors have been in demand since the advent of the steam age. Billions of such sensors are used every day to monitor fluid pressure in pipes, engines, hydraulic systems or in nature. Specialized sensors are also used to determine the pressure of solids or gases. A typical pressure sensor is about a cubic inch in size, although some can be a hundred or more times smaller, such as those used in microelectromechanical systems.
Most modern pressure sensors work on a principle called piezoresistance. Pressure causes a material to conduct electricity at a certain rate, leading to a specific level of charge flow associated with a specific level of pressure. This charge is fed to a wire that leads to a control panel and display for human analysis.
Conventional pressure sensors use film resistors, strain gauges, metal alloys or polycrystalline semiconductors as resistive media. These materials conduct more or less electricity based on geometric deformations in their structure. Since a linear increase in pressure does not lead to a linear magnitude of strain, calibration techniques must be used to determine the actual pressure. These are built into the vast majority of systems.
In the most sensitive single-crystalline semiconductor-based pressure sensors manufactured using conventional semiconductor technology, tiny strains can give rise to large changes in resistance. The change in resistance is not based on geometric strains in the conducting material, but on smaller and more delicate structural strains.
There are several types of pressure sensors. One is an absolute pressure sensor, which measures absolute pressure using a vacuum as a reference point. Another is a gauge sensor, which measures pressure with reference to the ambient atmospheric pressure. There are also differential pressure sensors, which measure the pressure difference between two contacts.
Usually, there is an intermediate medium between the medium to be measured and the pressure sensor itself. A metal diaphragm or hermetically sealed fluid chamber is often used. Especially when measuring the pressure of volatile or corrosive materials, such as hot oil in an engine, an intermediate layer is used to prevent damage to the sensitive sensing device. In addition to their nearly ubiquitous use in process equipment, pressure sensors are also used by naturalists to determine variables such as the depth of an ice floe or the density of a rock layer.
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