In the range between 4.6 - 4.9 μm, glass has an emissivity of almost 100 %. Above 5 μm, atmospheric influences such as humidity or water vapour affect the measurement. The CellaTemp® PX 15 has a blocking filter with a spectral sensitivity of 4.6 - 4.9 μm. This allows it to record the temperature from the area of the glass close to the surface. Interferences such as changes in thickness, different types of glass or changes in humidity do not affect the measured value at this wavelength.