A pressure sensor measures pressure, typically of gases or liquids. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude. Pressure sensors can alternatively be called pressure transducers, pressure transmitters, pressure senders, pressure indicators and piezometers, manometers, among other names.