André Blondel

André Blondel
André Blondel in 1888
Born	28 August 1863 Chaumont, Haute-Marne
Died	15 November 1938 (1938-11-16) (aged 75) Paris
Nationality	French
Fields	physicist
Alma mater	École polytechnique, École des Ponts et Chaussées
Known for	oscillograph
Notable awards	John Scott Medal (1898) Faraday Medal (1937)

André-Eugène Blondel (28 August 1863 – 15 November 1938) was a French engineer and physicist. He is the inventor of the electromechanical oscillograph and a system of photometric units of measurement.

Blondel was born in Chaumont, Haute-Marne, France. His father was a magistrate from an old family in the town of Dijon. He was the best student from the town in his year. He went on to attend the École nationale des ponts et chaussées (School of Bridges and Roadways) and graduated first in his class in 1888. He was employed as an engineer by the Lighthouses and Beacons Service until he retired in 1927 as its general first class inspector. He became a professor of electrotechnology at the School of Bridges and Highways and the School of Mines in Paris.

Very early in his career he suffered immobility due to a paralysis of his legs, which confined him to his room for 27 years, but he never stopped working.

In 1893 André Blondel sought to solve the problem of integral synchronization, using the theory proposed by Cornu. He determined the conditions under which the curve traced by a high-speed recording instrument would follow as closely as possible the actual variations of the physical phenomenon being studied.

This led him to invent the bifilar and soft iron oscillographs. These instruments won the grand prize at the St. Louis Exposition in 1904. They were more powerful than the classical stroboscope, invented in 1891 then in use. They remained the best way to record high-speed electrical phenomena for more than 40 years when they were replaced by the cathode ray oscilloscope. They paved the way for a greater understanding of the behavior of alternating current.

Blondel built a theory of rectification with asymmetrical electrodes. He demonstrated that there were three kinds of electric arc: the primitive arc of William Duddell, the secondary arc of Valdemar Poulsen, and a succession of oscillatory discharges.