Friedrich Heinrich Philipp Franz von Hefner-Alteneck (April 27, 1845 in

Aschaffenburg Aschaffenburg (; South Franconian German, South Franconian: ''Aschebersch'') is a town in northwest Bavaria, Germany. The town of Aschaffenburg is not part of the Aschaffenburg (district), district of Aschaffenburg, but is its administrative sea ...

– January 6, 1904 in Biesdorf near Berlin) was a German electrical engineer and one of the closest aides of

Werner von Siemens Ernst Werner Siemens (von Siemens from 1888; ; ; 13 December 1816 – 6 December 1892) was a German electrical engineer, inventor and industrialist. Siemens's name has been adopted as the SI unit of electrical conductance, the siemens. He foun ...

. He is largely remembered for the invention of the

Hefner lamp The Hefner lamp, or in German ''Hefnerkerze'', is a flame lamp used in photometry that burns amyl acetate. The lamp was invented by Friedrich von Hefner-Alteneck in 1884 and he proposed its use as a standard flame for photometric purposes with ...

, which provided the measure of

luminous intensity In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human e ...

used in Germany, Austria and Scandinavia from 1890 to 1942. The measure was called the ''Hefnerkerze'' (HK). The Hefnerkerze was superseded in the 1940s by the modern SI unit, the

candela The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous t ...

. He was elected a member of the Royal Swedish Academy of Sciences in 1896.

Notable Inventions

von Hefner-Alteneck's most notable inventions were all conceptualized during his time at Siemens. * Differential arc lamp - A type of automatic-feed carbon arc lamp * Drum armature - An efficient form of winding motor rotor coils * A telegraph keyboard * The

Gallery

File:Hefnerlampe.png,

inveted by Hefner-Alteneck

References

* *

External links

* 1845 births 1904 deaths Engineers from Bavaria Members of the Royal Swedish Academy of Sciences German electrical engineers People from Aschaffenburg {{Germany-engineer-stub