Operation Manual

10/ 2010 BENNING LUXMETER B
18
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2.1 Main application standards for field illuminance (lux) meters
There is a series of DIN (German Industrial Standards) standards with detailed
descriptions(definitions,precautions,measurements,worstvaluesetc)oflight
measuringindifferentprivatandpublicplaces.
DIN 5035 Illumination with artificial lights
- general precautions, measurements,
- terms, definitions and calculations,
- illumination in hospitals, schools, working places, offices,
- illumination in places with screens.
DIN 5034 Daylight in indoor rooms
- general precautions, measurements,
- terms, definitions and calculations,
- definition of minimum window size apartmans and loft rooms.
DIN 5037 Headlights
DIN 5044 Traffic illumination with street lights
DIN 33400 Workplace definition
DIN 67526 Lighting for sport facilities
3. General about illuminance
3.1 The origin of light
Light is a part of the electromagnetic waves. The electromagnetic spectrum
coversan extremelybroadrange,fromverylowfrequencies orinfra-frequen-
ciesovertheradiowaveswithwavelengthsofameterormoreononeside,to
x-raysandgamma-rayswithwavelengthsoflessthanabillionthofameter.But
the part of the light which we are interested in is the optical portion of the elec-
tromagneticspectrum(Figure1).Itliesbetweenradiowavesandx-rays,tobe
exact,itbordersoninfraredlightononesideandultravioletontheother.
Figure 1: Electromagnetic spectrum
3.2 Radiometric and Photometric values
The two approaches on how to measure light are:
- radiometric (based on energy),
- photometric(weightedtomatchtheresponsivityofthehumaneye).
The values that are weighted to match the responsivity of the human eye
(luminous flux, illuminance, luminance and luminous intensity) are measured by
photometric light units, the others (radiant flux, irradiance, radiance and radiant
intensity) by energetic units.
Thelumen,forexample,isthephotometricequivalentofthewatt.Ifonewants
tomeasurevisiblelight,one mustusephotometricquantities.Ifonewantsto
measure energy of light, one must use radiometric quantities.
3.3 Basic photometric definitions
Luminous Flux P [lm]
Luminousfluxisameasureofflowofvisiblelight.Theunitofthemeasureis
Lumen. There are two kinds of luminous flux:
- photopicflux(weightedtomatchtheresponsivityoftheeyeinnormallight
condition)
- scotopic flux (weighted to the sensitivity of the human eye in the dark
adapted state)
Luminous intensityI[lm/sr]
Luminous intensity is a measure of luminous flux emitted per unit solid angle.
Theunitofsolidviewingangleissteradian.Onesteradiancoversonesquare
meter on the surface of a sphere of 1 meter radius.
IlluminanceE[lm/m2=lux]
Illuminanceisthedensityofaluminousfluxincidentonagivenpointonasur-
face and is measured in Lux. 1 Lux is caused by a light source with the intensity
of 1 candela at the distance of 1 meter.
LuminanceL[lm/m2/sr=cd/m2]
Luminance is a measure of luminous flux emitted from an element of a surface
into a small solid angle per unit of projected area of the surface.
X-rays
UV-C UV-B UV-A
Visible light
380-770 mm
Ultraviolet light
100-380 mm
Infrared light
770 mm - 1 mm
Microwaves