The spectral response of the human eye changes with light intensity.
The eye has two distinctive spectral responses, which are defined
according to the brightness of the light entering the eye. The first
spectral response of the eye occurs under typical daytime lighting
conditions (photopic) defined for light intensity greater than 0.1
Lux. The second spectral response occurs under low light conditions
(scotopic) defined for light intensity between 0.01 and 0.0001 Lux.
Light intensity less than 0.0001 Lux is undetectable by the human
eye. The eye's shift from the photopic response to the scotopic
response is know as the Purkinje shift. The scotopic spectral
luminous efficiency curve peaks at 507 nm and it is normalized to 1
at that wavelength.
The power-like unit of brightness-sensation-producing ability of
light is lumen [lm]. The relationship between effective Watts and
scotopic lumen is now assumed to be 1754 lm/W. For example, 507-nm
monochromatic radiation flux of 0.0001W would carry the
scotopicluminous flux of 0.1754 lm. Please note, that photopic
spectral luminous efficiency as well as the conversion factor
between Watts and photopic lumens differ from their scotopic
counterparts.

|
Specifications
- Spectral response Follows CIE scotopic spectral luminous
efficiency curve (400-600nm) Figure 1
- Angular response 5% for angles <60°
- Range 200,000 scotopic mLux,
20,000 mft-cd, 120,000 µW/m2
- Display resolution 1 mLux
0.1 mft-cd 1 µW/m2
- Operating environment 32 to 120 °F (0 to +50 °C) no
precipitation
- Cable 5ft (1.5m)
- Diameter 1.6" (40.6 mm)
- Height 1.8" (45.8 mm)
- Weight 7.1 oz. (200 grams)
Analog versions of this detector are available See PMA1131
> Return to Detector Selection Guide
We Accept Visa, Master Card, Discover, and American Express Credit Cards for payment. |