Digital pressure gages are devices that convert applied pressure into signals. Readouts are then displayed numerically. Many pressure-gaging technologies are available. Devices that use mechanical deflection include an elastic or flexible element such as a diaphragm that responds to changes in pressure. Digital pressure gages that include a bridge circuit also use a diaphragm, but to detect changes in capacitance. Typically, strain gages or strain-sensitive variable resistors are used as elements in Wheatstone bridge circuits that perform measurements. Other digital pressure gages use pistons, vibrating elements, microelectromechanical systems (MEMS), or thin film to sense changes in pressure. Some devices use piezoelectric sensors to measure dynamic and quasi-state pressure. Generally, these sensors have two modes: charge and voltage. Charge mode generates a high-impedance charge and voltage mode uses an amplifier to convert the high-impedance charge into a low-impedance output voltage.