A vacuum pressure gauge in which a relatively large volume of a low-pressure gas is compressed to a small volume in a glass apparatus. The volume is reduced to an extent that causes the pressure to rise sufficiently to support a column of fluid high enough to read. This simple device, which relies on Boyle’s law, is suitable for measuring pressures in the range 103 to 10−3 pascal. It is named after Herbert McLeod (1841–1923), who invented it in 1874.
McLeod gauge.
A vacuum pressure gauge, devised by Herbert McLeod (1841–1923) in 1874, in which a relatively large volume of a low-pressure gas is compressed to a small volume in a glass apparatus. The volume is reduced to an extent that causes the pressure to rise sufficiently to support a column of fluid high enough to read. This simple device, which relies on Boyle’s law, is suitable for measuring pressures in the range 103 to 10−3 pascal.