Foot-candle

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Physical unit
Unit name Foot-candle
Unit symbol
Physical quantity (s) Illuminance
Formula symbol
dimension
system United States customary units
In SI units
Derived from Lumen , foot (unit)
See also: Lux (unit)

Foot-candle , also foot candle or footcandle , is an Anglo-American non- SI unit for illuminance or luminous flux densityin the United States customary units system.

definition

Currently, foot-candle refers to the evenly distributed illuminance of 1 lumen (lm) on an area of ​​one square foot . Unit symbols are fc, ftc, ft-c and now also lm / ft².

The physical unit is still used today in architecture, stage lighting, photography and the specification of photo sensors.

The Illuminating Engineering Society (IES) continues to specify the prescribed illuminance levels at workplaces and building parts intended for a restricted group of people or the public in foot-candle .

The conversion into the SI system of units is carried out using the formula: 1 fc = 1 ftc = 1 lm / ft 2  = 10.76391  lx .

history

First was foot-candle is a unit based on the brightness, a standard candle (engl .: standard candle ) generated in a walking distance to the flame.

For some time, the unit was based on the light of a candle internationally harmonized (engl .: international candle ) that falls on the area of one square foot in a walking distance.

Individual evidence

  1. a b c d e f Jan Gyllenbok: Encyclopaedia of Historical Metrology, Weights and Measures: Volume 1 . In: Science Networks Historical Studies . tape 56 . Birkhäuser, Springer International Publishing AG part of Springer Nature, Cham 2018, ISBN 978-3-319-57596-4 , p. 102 , doi : 10.1007 / 978-3-319-57598-8 (English, limited preview in Google Book Search [accessed on June 22, 2020]).
  2. a b Axel Rossmann: Simulated measurement technology: simulation without ballast for engineers and students . In: Structure formation and simulation of technical systems . Supplement band. epubli, Hamburg 2014, ISBN 978-3-8442-8868-1 , p. 66 ( limited preview in Google Book Search [accessed June 22, 2020]).
  3. a b Commercial Lighting 101: What is a Foot Candle? In: FSGi.com. Facility Solutions Group, accessed June 22, 2020 .