Pro-Lite has provided the first 3m diameter integrating sphere photometer in Europe for DW Windsor.
The sphere, which the company claims is the largest and most accurate of its type, is operating at DW Windsor’s manufacturing facility in Hoddesdon, Hertfordshire.
The Illumia sphere is supplied by US manufacturers, Labsphere Inc, and enables DW Windsor to accurately measure the colour and brightness of even the very largest streetlight luminaires.
“Our custom-designed Labsphere integrating sphere puts us in the unique position of having one of the largest and possibly the most accurate systems of its type in the UK,” said Alan Grant, DWW’s Design and Development Director.
“Unlike other cube or geodesic shapes or spheres coated in ordinary reflectance paints our Labsphere system is coated with their special high reflectance paint so we can deliver accurate, repeatable results regardless of the size of the fitting, type of light source or shape of light beam produced.”
[We have] one of the largest and possibly the most accurate systems of its type in the UK
Used to measure the luminous flux (lumens), colour temperature and colour rendering of luminaires, the 3m Integrating Sphere and spectroradiometer is one of the most accurate methods to measure the light output from LEDs, including the very large Solid State Lighting (SSL) luminaires, designed for street lighting applications.
With standard regulations calling for all integrating spheres to be at least fifty times larger than the luminaire to be measured, to ensure good spatial integration and acceptable accuracy rates, the investment of the sphere was a vital addition to DW Windsor’s laboratory spurred by its on-going commitment to provide accurate luminaire data and prevent disillusionment with LEDs as a light source.
The sphere which Pro-Lite developed in close collaboration with Labsphere is based on six segments, assembled and then coated with special high reflectance Spectraflect integrating sphere paint at DW Windsor’s laboratory.
The segments make up two 3m diameter half spheres – one fixed to the laboratory floor while the other opens under gas assistance and runs on a track to enable interior access for 4pi flux measurements. When closed the sphere has a consistent light-tight seal.
The sphere can support luminaires weighing up to 20kg in either a base-up or base-down orientation while a port on the side of the sphere can measure 2pi flux with the luminaire positioned on the outside. A temperature sensor records the ambient temperature inside the sphere, an auxiliary lamp adjusts the readings to allow for light absorption from the samples being tested.
The sphere is calibrated using Labsphere lamp standards of spectral flux under ISO 17025 laboratory quality management system and the NAVLAB accreditation scheme which is equivalent to UKAS accreditation. This ensures DW Windsor’s measurements are traceable to international standards.
