L203 Photometer
Irradian Limited
11
(CIE Cos-112 filter ring fitted)
Illuminance is the measurement of photometric light per unit area,
lumens per metre, lux, or lumens per square foot, footcandle. For most
applications the measurement plane is horizontal and a cosine corrected
diffuser is fitted to the front of the detector assembly. If the working
surface is not horizontal then placing the detector on or parallel to the
worktop is a more representative measurement of the illuminance.
Note that all the light sources in the hemisphere above the detector will
contribute to the illuminance measurement. The sources may be
obvious, lamps or windows or even walls or other reflecting surfaces.
Take care not to shadow the detector during all illuminance
measurements.
1) Set up the photometer as outlined in section 3 with the illuminance
filter ring fitted and the units set to either lux or fc.
2) Place the detector at the measuring point and record the value on the
display. If the light levels are low it may be necessary to switch on the
display back light.
3) The display can be read directly for light levels from 0.0000 lux to 199
990 lux or 0.0000 to 19 999 fc. Note however that for illuminance
values of 20 000 to 199 990 lux, the x10 LED will illuminate and the
displayed value must be multiplied by 10.
CONVERSION FACTORS
1 lux
=
0.0929 footcandle
1 lux
=
1 candela @ 1 metre
1 lux
=
d² candela @ d metres