Glossmeter
A gloss meter (also reflectometer or gloss meter ) is an instrument with which the splendor of a flat surface, such as plastic, paper or paint is measured. Here, as a brightener, a ratio between the eingestrahltem and the reflected light from the surface at the angle of specular reflection is understood. Great find use Glossmeters in process control in the production of paper and in quality assurance in the automotive industry.
Construction of a gloss meter
A gloss meter comprises a light source and a lens, the parallel light is irradiated onto a sample surface and a receiver with a lens, aperture and photodetector which receives the reflected light and measures quantitatively. With a gloss meter directional light is irradiated at a defined angle to the sample surface. At the same angle a detector receives the reflected light radiation from the sample surface. In the physical sense, the measured value is the integral of the reflection indicatrix of the test specimen for a particular through the apertures of illumination and detector optics solid angle dar.
Unit of measurement
The unit of a gloss meter is GU (gloss units or gloss unit ). The scale for the brilliant unit based on the reference value is achieved when a polished black glass standard with a defined index of refraction. During the calibration of this reference value is set as 100 GU. The second reference point of the scale is 0 GU, the measured value, which is reached at a perfect matte finish. The gloss levels of most non-metallic surfaces (paints, paper, ...) is in the range between 0 and 100, however, significantly higher values of up to 2000 GU can be achieved for polished metal surfaces and mirrors. For transparent materials, however, the reflectometer can be very low. In these cases, however, mostly used no gloss meter, but the reflectance, ie the ratio of reflected to incident light, specified for a particular angle.
MEASUREMENT
The angle at which the measurement is determined depending on the material and the expected degree of gloss in the relevant standards. It is selected such that the sensitivity of the detector as well as possible is utilized. In several standards, the three angles of 20 °, 60 ° and 85 ° are specified. According to ISO 2813, the gloss level is initially measured at an angle of 60 °. If the measured value in this first measurement above 70 GU of the measurement angle is reduced to 20 °. If it is below 10 GU it is increased to 85 °. Otherwise, the reading can be taken. Modern Gloss meters perform this angle adjustment automatically.
Next 20 °, 60 ° and 85 ° is specified an angle of 75 ° for ceramics, plastic films, textiles and anodized aluminum, an angle of 45 ° and for papers.
In practice it is not always measured after this specified in the standard sequence. Some users measure in the absence of a 20 ° - meter consciously or high gloss with the 60 ° measuring angle or evaluate measured values with decimal places, although in the standard as characteristic values for the measuring system analysis repeatability of 1 GU ( at 60 ° and 85 ° ) or 2 GU must be achieved (at 20 ° ) with a confidence interval of 95%.
Explanation of benefits
To ensure a homogeneous overall impression with a product that consists of several components, the knowledge of the gloss value of the individual parts is very relevant. Product examples are found for example in the automotive industry, where the components of the vehicle interiors are manufactured in different production stages and then assembled. In the final product, no difference between the individual components in terms of their visual appearance is (next to shine and color and texture) are visible.
" A few decades ago use was made of this [to measure the gloss ], the visual comparison with a set of graded in their luster gloss panels (eg after Boller ). The gloss value was still given to " gloss percent ." 'This provision of a gloss value is obviously very strong subjective and influenced the validity of the user's experience and ability. A gloss meter, however, represents a measured value available, with the gloss of a surface can be determined quantifiable and reproducible.