The pressure of a sample of gas inside a container is measured by using a pressure
gauge, which is a device with electrical properties that depend on the pressure. For
instance, a Bayard–Alpert pressure gauge is based on the ionization of the molecules
present in the gas and the resulting current of ions is interpreted in terms of the
pressure. In a capacitance manometer, the deflection of a diaphragm relative to a fixed
electrode is monitored through its effect on the capacitance of the arrangement.
Certain semiconductors also respond to pressure and are used as transducers in solidstate
pressure gauges.