Barograph

A barograph is a recording aneroid barometer. A barograph is used to measure pressure. The pointer in an aneroid barometer is replaced with a pen. It produces paper or foil chart called a barogram that records the barometric pressure over time.

Barographs use one or more aneroid cells acting through a gear or lever train to drive a recording arm that has at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper using ink, held in a nib. The recording material is mounted on a cylindrical drum which is rotated slowly by clockwork. Commonly, the drum makes one revolution per day, per week, or per month and the rotation rate can often be selected by the user.