Two-color pyrometer series, the device works in two spectral ranges at the same time and determines the temperature by calculating the radiance ratio. In this method, it is not necessary to know the emissivity of the material, since the radiation ratio remains constant in the neutral attenuation of infrared radiation (caused by dust, smoke, etc.).

Contaminated viewing glasses or dust and smoke make the measurement largely unaffected.
Measurement objects smaller than the pyrometer spot size can be measured
Short pyrometer wavelength range ideal for metal measurements
Fiber versions can be used in ambient temperatures up to 250°C (on the optical head) without additional cooling.
Targets with the same emissivity at both wavelengths can be measured without setting the emissivity slope.
Emissivity changes must have the same effect on both channels (wavelengths).
When measuring objects with different emissivities at the two wavelengths, such as bare, unoxidized metal surfaces, the emissivity ratio must be set for accurate temperature measurements.