The emissiometer consists of an integrating sphere, glowbars as sources of thermal radiation and 3 detectors, which are sensitive for wavelengths in the range of 3,9µm, 5,1 µm, and around 10µm (from 8 µm to 14 µm). The radiation from the glowbars is homogeneously distributed inside the integrating sphere which serves as a diffuse radiation source.
The detectors are installed at an angle of 12° to the normal of the sample surface. The radiation which is reflected by the sample is measured. The calibration is done by measuring 2 reference samples with known emittance values in the mentioned wavelength range: a sample with a high emittance and a sample with a low emittance or ideally with an emittance close to the emittance of the samples to be measured. The weighting of the thermal emittance is performed for a pre-selected operating surface.