Vacuum Measurement over the Course of Time — From Torricelli to bakeable digital wide‐range sensors for measurement from 103 to 10‐12 mbar
Since the first vacuum measurement in the middle of the 17th century, various methods have been developed to measure total vacuum pressures. After establishing the kinetic theory of gases in the late 19th century, the development of different indirect measurement methods started. Hereby, the lower detection limit — located in the fine vacuum range for direct methods such as mercury tubes — has been continuously shifted down to the ultrahigh vacuum range. The combination of different measuring principles in wide‐range sensors soon allowed the measurement over extended pressure ranges — with just one device. Latest developments have yielded to the creation of a new generation of vacuum measurement: passive bakeable wide‐range sensors. Consisting of optimized ionization‐sensors and a novel integration of a digital Pirani principle, they are the first vacuum sensors for precise total pressure measurement over 15 decades — from atmosphere down to the ultra‐high vacuum (10+3 to 10‐12 mbar).