L203 Photometer
Irradian Limited
1
The Irradian L203 Digital Photometer is a portable instrument designed
for accurate measurement of luminous incidence or illuminance in lux (fc,
foot-candle) and luminous intensity or luminance in cd.m
-2
, candela per
square metre (fL, foot-Lambert). The model L203-LUX is available for
illuminance measurements only.
The photometers comprise of a hand held display unit, a detector
/amplifier assembly with connecting cable, an illuminance filter ring and a
luminance field of view probe. The sensor is a large area silicon
photodiode with excellent linearity and long term stability. The Irradian
photopic filter ring and photopic field of view probe, fitted to the front of
the silicon detector give a response which closely matches the human
eye response outlined by the CIE V
λ
curve. This precise colour
correction gives high accuracy of photometric measurements from light
sources with different spectral distributions (see Calibration section).
For illuminance measurements, the Irradian photopic filter ring with
cosine corrected diffuser (model CIE Cos-112) is fitted to the detector
assembly. This will integrate light from all sources in the hemisphere in
front of the detector. Before leaving the factory, the instrument is
calibrated to read directly in lux and fc (foot-candle).
The L203 Photometer can also measure luminance directly. In this mode
of operation, the illuminance filter ring is removed from the detector
assembly and replaced with either a CIE FOV-112 luminance probe (with
a defined field-of-view of 6°) or a contact CIE FOV-101 CRT luminance
probe. In either case, where the luminance varies across the field of
view or probe area, the meter reading will represent the average
luminance. The photometer can measure in either cd.m
-2
or fL (foot-
Lambert).