Our directional photometry facility provides a calibration service for measurement of luminous intensity, illuminance, luminance and correlated colour temperature quantities for both sources and detectors.
We can measure illuminances from about 0.1 lx to more than 50 klx and luminances from below 1 cd m-2 to around 20 000 cd m-2, for many different types of source including LEDs and other SSLs. Measurements of sources are performed using a high accuracy photometer, which has been specially designed and built at NPL to closely match the spectral response of the human eye, as described by the V(λ) function. Illuminance and luminance meters are calibrated using tungsten-based reference sources, in accordance with the requirements of standards such as BS EN 13032 and ISO/CIE 19496, with additional spectral responsivity calibration if required in order to provide information on performance with other types of light source.
All our photometric measurements are traceable to the UK's primary standard for the measurement of optical radiant power (cryogenic radiometer) through lamps and detectors which form part of NPL's luminous intensity scale. We can also supply calibrated lamps for luminous intensity, illuminance and correlated colour temperature measurement.
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