Delta OHM HD 9221 Gebrauchsanleitung Seite 43

LP 9221/LUM 6
Photometric probe for measuring LUMINANCE.
This is the quantity of light visible (with correction according to the human
eye) in the solid angle emitted in the area of a source of light.
The probe opening diameter is 18 mm, measuring angle 6°.
The measuring range is from 0 to 1999 x 10
2
per cm ).
- The CANDLE (cd) is the light intensity in a specific direction of a source
that emits monochrome radiation at a frequency of 540 x 10
whose energetic intensity in that direction is 1/683 W/sr.
- The STERADIAN (sr) is the solid angle which, with its vertex in the cen-
tre of a sphere, subtends a spherical cap with an area equal to the squa-
re of the radius.
- LUMINANCE or EMITTANCE is the relationship between the light inten-
sity emitted in a certain direction and the surface that emits it projected
onto a plain perpendicular to the same direction; the measuring unit
2
is the cd/m (candle/square metre) or its submultiple cd/cm
2
10,000 cd/m ).
Light flux = lumen (lm) = cd/sr
Illuminance = lux (lx)
Luminance = nit (nit)
2
= lm/m
2
= cd/m
– 40 –
3 2
candles/m (199.9 candles
6°
2
ENGLISH
12
Hz and
2
(1 cd/cm =