Pressure transmitters translate low-level electrical outputs from pressure sensing devices to higher-level signals that are suitable for transmission and processing. They use many different sensing technologies and can measure the pressure of liquids and/or gases. Mechanical deflection devices such as diaphragms, Bourdon tubes or bellows consist of an elastic or flexible element that is deflected mechanically by a change in pressure. Devices that use sealed pistons or cylinders are also available. Strain gauges are often bonded to a larger structure that deforms as pressure changes. Piezoresistive devices sense shifts of electrical charges within a resistor. Piezoelectric pressure transmitters measure dynamic and quasi-static pressures. Their common modes of operation are charge mode, which generates a high-impedance charge output; and voltage mode, which uses an amplifier to convert the high-impedance charge into a low-impedance output voltage. Thin film devices consist of an extremely thin layer of material, usually titanium nitride or polysilicon, deposited on a substrate. Pressure transmitters that use microelectromechanical systems (MEMS), variable capacitance, and vibrating elements are also available.