Window material and transmittance correction

A window may be required between the radiation thermometer and the object to be measured.

Select a window material that sufficiently penetrates the measurement wavelength of the radiation thermometer to be used. The table below shows the types and window combinations of the thermometers we handle.

Other types of window materials can be used. Contact us if you do not know how to obtain window materials or any other information.

If this windowing material is in the middle of the optical path, multiplying the emissivity of the material by this transmittance determines the effective emissivity Ew of the material. (Refer to the figure below.)
If this value is set to the radiation thermometer, the window-corrected temperature is displayed.

Ew＝　E　ｘ　Tw

E:　Emissivity of the material
Tw：Transmittance of windows
Ew：Effective emissivity corrected by windows

If the transmittance at the wavelength to be measured is known in advance, the window material is corrected by adding that value, but if there is a stable heat source, it can be measured easily.

The following is a concrete example.

Let’s assume that the radiation thermometer IS140 (measured wavelength: 0.7 to 1.1μm) is pointed at a given heat source and the emissivity is 600℃ at a setting of 100%.
(For transmittance measurement, the emissivity should be kept at the 100% setting.)
When a window material (for example, quartz) is placed in the optical path to reach 597℃, the emissivity is corrected so that the temperature becomes 600℃. At this time, if the emissivity becomes 94%, the transmittance of the window material is 94%.