what are the two types of instruments measure air pressure
A barometer is any instrument that measures air pressure. Barometers come in two basic forms: the aneroid barometer and the mercury barometer. Aneroid barometers use cells that expand and contract as air pressure changes. Air pressure is measured by attaching a needle into these cells. A mercury barometer, on the other hand, uses mercury that rises and falls in response to air pressure changes. Barograph