Illuminance meters are typically calibrated over the range 10 lux to 3000 lux against secondary standard lamps at a colour temperature of 2856 K. Meters suitable for this calibration usually consist of a silicon diode detector fitted with a CIE photopic correction filter and connected by a flexible cable to a digital or high quality moving coil readout.
Luminance meters can be calibrated over the range 5 cd/m2 to 800 cd/m2 using a secondary standard lamp with a colour temperature of 2856 K and a standard white reflector.
- Luminous intensity of light sources including LED devices can be calibrated using a calibrated light meter.
- Colour temperature, CIE chromaticity coordinates and the colour rendering index of light sources are measured using a calibrated spectroradiometer. Spectral irradiance measurements are made over the wavelength range 360 nm to 830 nm at 1 nm intervals.
The CIE chromaticity coordinates and luminance factor of surfaces and fabrics are measured using a xenon arc light source, a calibrated spectroradiometer and a reference reflector. Spectral reflectance measurements are usually made in the 0°/45° or 45°/0° measurement geometry and the chromaticity coordinates and luminance factor are calculated for the following standard illuminant sources: A, C, D55 and D65.
Fluorescent fabrics are measured with the xenon arc source filtered so it is a close approximation to the D65 standard illuminant source spectrum.
Materials measured using these methods include life jacket fabrics, fluorescent fabrics for high visibility clothing, road lane markers and paints.
The retroreflective performance of sheeting and sign materials can be determined for observation angles of 0.2º to 1º and a range of entrance angles to 40º. The materials C.I.L. values and C.I.L/m2 can be calculated.
For information on these services please contact Neil Swift.