A pressure sensor determines pressure, usually of liquids and gases. Pressure is a manifestation of the force needed for stopping a fluid from expanding and is normally expressed as force per unit area. A pressure sensor acting generally as a transducer produces a signal as a function of the imposed pressure. Such signals can be considered to be electrical. Pressure sensors are used in thousands for monitoring and control of daily applications. They can also be used to determine indirectly other variables like gas/liquid flow, water level, speed, and altitude. Alternatively, pressure sensors can be called pressure transducers, pressure senders, pressure transmitters, pressure indicators and manometers, among others.
There are pressure sensors with drastically varying technology, performance, design, application, cost and suitability. Worldwide there may be more than 50 technologies and minimum 300 companies that make pressure sensors. There is as well a kind of pressure sensors which are made to determine in a dynamic mode the capture of very high speed pressure changes. This kind of sensor can find example applications in the determination of combustion pressure in a gas turbine or in an engine cylinder. These sensors are made usually by using piezoelectric materials like quartz. Pressure sensors used in traffic enforcement cameras work in a binary way (on/off), which are also called pressure switches.