#66: Looking through sight windows with LoE filter models
Commonly, many types of furnaces are equipped with sight windows to permit visual inspection of the processing of the materials. These windows would conveniently provide a means for monitoring the temperature if the IR sensor could deliver reliable readings through the glass. Such glass can be normal window glass, tempered glass, quartz, etc.
LoE IRt/c models can “see through” such windows and will provide reliable readings if the losses are not too great. The adjustability feature of these models allow them to be calibrated to include the loss through the window. As a general recommendation, targets above about 500°C (932°F) should provide good results, but the only way to be sure is to actually install the appropriate IRt/c and monitor results. If there is insufficient signal to read out the correct temperature, the OFFSET adjustment on the readout device may be used to add signal.