Barograph

A barograph ( ancient Greek βάρος Baros " Heavy Weight " and γράφειν gráphein " write") is a measuring instrument that records the time history of the air pressure on a paper -covered drum. The resulting curve is called barogram. On the right side above such barogram can be seen. The evaluation of the barogram can give the skilled hints for future weather trends. In particular, one often finds barograph on ships. Strong pressure drop within a period of one to three hours may be an indication of impending strong wind or storm. For the actual measurement it is a barometer.

Barograph play in aviation, particularly in cross-country flying with gliders, a role. Then, however, are often also spoken by a barograph. Since the air pressure decreases with altitude is well known, the altitude profile of the flight can be analyzed after landing. For some time -haul flights are however recorded amplified using GNSS loggers, leading to a gradual displacement of the analog barograph from the competition flying.

There is also the barograph register the air pressure history on a disc, or electronic barograph where the barogram appears on a ( LC) display.

Three -day barograph, as used by the Meteorological Service of Canada ( Cambridge Bay, Nunavut, July 2005)

Schiffsbarograph from the USSR

Detail of five aneroid capsules used in a barograph

A not insignificant problem in atmospheric pressure recording are mechanical vibrations of the measurement setup. Therefore, mechanical Trommelbarographen are also often attenuated. In electronic barograph the damping either the electronics itself or by the only discrete measurement is achieved. When using barograph on ships in seas also also occur due to changes in elevation through the waves. A change in height of 8 m corresponds to an absolute pressure change of 1 hPa This " rocking " of the trace should also be removed from the actual measurement signal.

Recording the change in pressure (mechanical or electronic ) is used either in series aneroid which add their low Wegdeformationen by the series connection, or piezoelectric devices which due to induce by the pressure change, an electrical voltage signal can be, in turn, amplified and registered. A general problem here is the temperature compensation of the measurement setup. A change in temperature at constant pressure should not cause any change in the measurement signal.

The recording of the atmospheric pressure is a necessary and often useful indicator for the local weather forecast. The absolute value of air pressure is almost irrelevant to the existing weather conditions. Mainly the pressure changes are extremely useful indicators of changes in the weather.