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Area Lighting / Visual signalling

IEV ref 845-31-025

en
Allard's law
law relating the illuminance, Ev, produced on a surface (which is normal to the direction of the light source and sufficiently distant for the light source to be considered as a point source) by a light source to the luminous intensity, Iv, of the light source in the direction of the surface, to the distance, d, between the surface and the light source, and to the atmospheric transmissivity, T, which is assumed to be uniform

E v = I v d 2 T d/ d 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaWGubWaaWbaaSqabeaacaWGKbGaai4laiaadsgadaWg aaadbaGaaGimaaqabaaaaaaa@450F@

where d0 is the length specified in the definition of T

Note 1 to entry: The formula in the definition is sometimes written:

E v = I v d 2 T δ MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaWGubWaaWbaaSqabeaacqaH0oazaaaaaa@4347@

where the exponent, δ, in Tδ is the numerical value of the distance, d, measured with d0 as "unit".

Note 2 to entry: Taking into account the relationship between atmospheric transmissivity, T, and meteorological optical range, v, given in Note 2 to entry of the definition of "meteorological optical range", Allard's law can also be written as:

E v = I v d 2 ( 0,05 d/v ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaaMe8UaaiikaKaaajaaicdacaGGSaGaaGimaiaaiwda kmaaCaaaleqabaGaamizaiaac+cacaWG2baaaOGaaiykaaaa@4986@ .

Note 3 to entry: This entry was numbered 845-11-27 in IEC 60050-845:1987.


fr
loi d'Allard, f
loi associant l'éclairement lumineux Ev, produit sur une surface (perpendiculairement à la direction de la source de lumière et à une distance suffisante pour que la source de lumière soit considérée comme source ponctuelle) par une source de lumière, à l'intensité lumineuse Iv, de la source de lumière dans la direction de la surface, par rapport à la distance, d, entre la surface et la source de lumière, et la transmissivité atmosphérique, T, réputée uniforme

E v = I v d 2 T d/ d 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaWGubWaaWbaaSqabeaacaWGKbGaai4laiaadsgadaWg aaadbaGaaGimaaqabaaaaaaa@450F@

d0 est la longueur spécifiée dans la définition de T

Note 1 à l'article: La formule dans la définition est parfois écrite sous la forme:

E v = I v d 2 T δ MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaWGubWaaWbaaSqabeaacqaH0oazaaaaaa@4347@

où l'exposant, δ, dans Tδ est la valeur numérique de la distance, d, mesurée avec d0 comme "unité".

Note 2 à l'article: Compte tenu de la relation entre la transmissivité atmosphérique T, et la portée optique météorologique, v, donnée à la Note 2 à l'article de la définition "portée optique météorologique", la loi d'Allard peut aussi s'écrire sous la forme:

E v = I v d 2 ( 0,05 d/v ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgaruWqVvNCPvMCG4uz 3bqee0evGueE0jxyaibaieYdi9WrpeeC0lXdh9vqqj=hEeeu0lXdbb a9GqFj0xb9Lqpepeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9 q8qiLsFr0=vr0=vr0db8meaabaGacmGadiWaaiWabaabaiaafaaake aacaWGfbWaaSbaaSqaaiaabAhaaeqaaOGaeyypa0ZaaSaaaeaacaWG jbWaaSbaaSqaaiaabAhaaeqaaaGcbaGaamizamaaCaaaleqabaGaaG OmaaaaaaGccaaMe8UaaiikaKaaajaaicdacaGGSaGaaGimaiaaiwda kmaaCaaaleqabaGaamizaiaac+cacaWG2baaaOGaaiykaaaa@4986@ .

Note 3 à l'article: Cet article était numéroté 845-11-27 dans l'IEC 60050-845:1987.


ar
قانون ألارد

cs
Allardův zákon

de
Gesetz von Allard, n

it
legge di Allard

ko
알라드 법칙

ja
アラードの法則

nl
nl wet van Allard

nl
be wet van Allard, m

pl
prawo Allarda, n

pt
lei de Allard

zh
阿拉德定律

Publication date: 2020-12
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