L203 Photometer
Irradian Limited
15
Photometry is the measurement of visible light. Irradian's photopic filter
and photodiode closely matches the response of the standard human
eye as published by the CIE (CIE V
λ
). The spectral response of the
photodiode detector with the photopic filter ring is plotted beside the ideal
CIE response.
SD222 + CIE Cos-112
Relative Response
Figure 1
Photometers which do not closely match the response are often supplied
with correction factors for different types of lamps and light sources. This
means that the user has to identify the type of source being measured
and correct the meter reading. This procedure becomes more unreliable
when sources are mixed for example office lighting mixed with daylight
through a window.
The response of the Irradian photometer is such that the error for a wide
variety of sources is typically < 2%.