McLeod gauge
/məˈklaʊd ˌɡeɪdʒ/(US McLeod gage)
noun
A type of mercury-in-glass manometer for the absolute measurement of low pressures, in which a known volume of the gas to be measured is compressed by the mercury into a small volume, and the resulting pressure is found from the height of the column of mercury it supports.
Origin
Late 19th century; earliest use found in James Edward Henry Gordon (1852–1893), electrical engineer. From the name of Herbert McLeod, English scientist, who invented the instrument in 1874 (Philos. Mag. 48 110) + gauge.