When you do infrared inspections through IR windows, not all of the infrared energy emitted from the target is transmitted through the optical material in the window. If you know the transmission percentage of the window, adjust the transmission percentage in the Imager or in SmartView software to improve the accuracy of the measurement. When you do not do infrared inspections through an IR window, set the Window % to 100 % to disable the correction percentage.
If you don't know the window transmission percentage. Take a temperature without the window at 100%. Now take a temperature with the window. Reduce the window transmission percentage till both temperature values match. IR windows will very between 40% - 60% transmission rates.