A barograph is a recording
aneroid barometer. It produces a 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. 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.
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