Part 3. Piston Gages

The early seventeenth century was a time of great progress in science and it is perhaps not surprising that the great contemporaries Galileo, Descartes, Boyle, and many others devoted some of their time to the study of the properties of the atmosphere. In 1644 Torricelli described his famous measurement of atmospheric pressure in a letter50 to his friend Michelangelo Ricci. Within 25 years followed the famous experiments by Pascal and Perier (1648), Guericke (1672) and Boyle (1669). One hundred years later, in 1764, James Watt began to lay the foundation for the Steam Tables by making the first careful measurements of the properties of steam. During this time mercury manometers were used to determine pressure. About 1800 Richard Trevithik built the first high pressure steam engine which proved to be much more efficient than Watt’s and Newcomen’s machines; from then on new types of gages were required to cover the pressure range of interest for industrial applications. In 1846 the German railway engineer Schinz34 had discovered that a curved tube of elliptical cross section would change its curvature when subjected to internal pressure and by 1848 steam pressure gages based on this principle were in use on locomotives in Germany19. In 1847 both Schinz46 and Bourdon6 patented devices which are now universally known as Bourdon gages. In 1846 Galy-Cazalat20 described the first piston manometer, a combination of mercury manometer and hydraulic multiplier.