A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding and is usually stated in terms of force per unit area.
A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. For this article, such a signal is electrical. Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude.
Pressure sensors can be called pressure transducers, pressure transmitters, pressure senders, pressure indicators, piezometers, and manometers, among other names. Pressure sensors vary drastically in technology, design, performance, application suitability, and cost. A conservative estimate would be that there may be over 50 technologies and at least 300 companies making pressure sensors worldwide. There is also a category of pressure sensors designed to measure in a dynamic mode to capture very high-speed pressure changes.
Examples of this type of sensor include measuring combustion pressure in an engine cylinder or a gas turbine. These sensors are commonly manufactured out of piezoelectric materials such as quartz. Some pressure sensors, such as those found in some traffic enforcement cameras, function in a binary (off/on) manner, i.e., when pressure is applied to a pressure sensor, the sensor acts to complete or break an electrical circuit. These types of sensors are also known as pressure switch.