barograph

A barograph is a recording barometer that provides a continuous, time-stamped record of atmospheric pressure. Traditional barographs use one or more aneroid capsules whose size changes with ambient pressure; motions from these capsules are transmitted by a linkage to a writing pen that traces a continuous barogram on chart paper wrapped around a rotating drum.

Construction and operation: The chart drum is driven by a clockwork mechanism and typically completes a full rotation in a period such as one week or 24 hours, depending on the design. The pen’s trace, known as a barogram, shows pressure on the vertical axis and time on the horizontal axis. Temperature can affect measurements, so many barographs include temperature compensation or are used in temperature-controlled enclosures. The chart is periodically renewed, and the instrument requires regular calibration for accurate readings.

Types and variants: Mechanical barographs use aneroid sensors; electrobarographs replace the writing mechanism with electronic sensors and an electromechanical recorder or digital data logger. Modern barographs may use solid-state pressure sensors with electronic recording, producing digital barograms or data streams suitable for archival and analysis.

Uses: Barographs have been widely employed in meteorology, maritime navigation, and aviation to obtain long-running records of pressure trends, which aid in weather forecasting and storm analysis. In historical contexts, barograms provide valuable climate records and support synoptic weather reconstruction.

History: The aneroid barometer was developed in the 19th century, with Lucien Vidie credited for the invention around 1843. Barographs expanded the utility of pressure measurements by enabling continuous, time-based records, a central tool in early modern meteorology and maritime weather observation.

See also: barometer, barogram, aneroid barometer.