barometric scale

barometric scale

barometric scaleclick for a larger image
A scale on the dial of a sensitive altimeter. A pilot sets the barometric pressure level and uses it to measure the altitude shown on the altimeter. When existing pressure (QNH) is set, the altimeter reads the indicated altitude, and when the standard sea level pressure (1013.2 hectopascals, 29.92 in, or 760 mm) is set, the altimeter indicates the pressure altitude. The barometric scale appears in the Kollsman window of the altimeter. See also QNH.