Marcello Pirani
Marcello Stefano Pirani (July 1, 1880 – January 11, 1968) was a German physicist known for his invention of the Pirani vacuum gauge, a vacuum gauge based on the principle of heat loss measurement. Throughout his career, he worked on advancing lighting technology and pioneered work on the physics of gas discharge.
Marcello Pirani was born on July 1, 1880, in Berlin. Starting in 1899, he studied mathematics and physics at the University of Berlin. In 1903, he was granted a PhD for his measurements of the dielectric constant of solids in the group of Emil Warburg. He then moved to the Technical University of Aachen as an assistant at the Physikalischen Institut of this University.
In 1904, he joined the light bulb factory (Glühlampenwerk) of Siemens & Halske AG in Berlin where he remained for the next fifteen years. At the age of 25, in 1905, he was promoted head of the development lab of the light bulb factory.
In 1906, he made his most important invention with the development of a new type of vacuum gauge that today bears his name, the Pirani gauge. It is based on measuring the pressure dependence of heat loss from a hot wire by heat transfer to the surrounding gas and walls. In particular, it employs the change in resistivity of the heated wire (in Pirani’s original work consisting of Tantalum and Platinum, today, Tungsten, Platinum or Nickel is commonly used) with temperature to determine the heat loss. Its useful measurement range lies within 10−4mbar up to 1000mbar.
Four years later, he finished his habilitation on optical measurements of high temperatures and studies on the relationship between temperature and emissivity of hot solids and becomes private docent at the Technical University Berlin-Charlottenburg. During the first world war, he enlisted in the army to deal with scientific-technical problems such as wireless telegraphy.
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