<Li> Hair spring to preload the gear train to eliminate gear lash and hysteresis . </Li> <P> A second type of aneroid gauge uses deflection of a flexible membrane that separates regions of different pressure . The amount of deflection is repeatable for known pressures so the pressure can be determined by using calibration . The deformation of a thin diaphragm is dependent on the difference in pressure between its two faces . The reference face can be open to atmosphere to measure gauge pressure, open to a second port to measure differential pressure, or can be sealed against a vacuum or other fixed reference pressure to measure absolute pressure . The deformation can be measured using mechanical, optical or capacitive techniques . Ceramic and metallic diaphragms are used . </P> <Dl> <Dd> Useful range: above 10 Torr (roughly 1 Pa) </Dd> </Dl> <Dd> Useful range: above 10 Torr (roughly 1 Pa) </Dd>

Which units are used to measure pressure in the atmosphere throughout europe