About Barometers

The story of the barometer began in 1643, when Torrecelli discovered that the pressure of the atmosphere would support a column of mercury approximately 29" (737mm) high. Using a barometer to predict the weather domestically did not start until around 1675, although they were in use by scientists from 1644 - after Boyle developed Torricelli's experiment into a usable instrument (as opposed to experimental apparatus) (mainly for measuring heights, as air pressure decreases the higher you go). During this period it was realized that there was a connection between local weather conditions and the air pressure, and, with the British obsession with the weather, there was a ready market for these instruments.

The first domestic barometers (stick) were simple affairs and did not last long, but as their popularity increased, they became more decorative and designed as attractive pieces of furniture as well as useful instruments. Around 1663 Hooke devised the wheel barometer, but it only became popular in the mid 1700's and to a large extent replaced the stick. A major problem with mercury barometers was the lack of portability, they must be transported with great care, and precautions have to be taken to stop spillage of the mercury. This was not such an issue with domestic barometers as for the scientific community, and there were various designs attempting to make them more portable. A major change arrived in the form of the aneroid (without liquid) mechanism, when in 1843, Vidie devised a vacuum chamber connected to the pointer by levers to amplify the movement. This was the next 'upgrade' and they could be moved about with no problems, indeed small pocket barometers, the size of a fob watch were manufactured, and were used by surveyors to measure the height of hills, etc. Today's barometers used by engineers & scientists are electronic with digital readouts, using modern techniques, such as the Druck 'micro machined resonant silicon pressure sensor' and are extremely accurate, measuring pressure changes as little as 0.01mbar (0.0003 in. mercury).