Design and evaluation of a detection system for external water condensation on low U-value windows

A laser detection system was developed and mounted in Uppsala, Sweden. A blinking commercial laser was set up so that the beam hit the surface to examine. A photodiode detects part of the beam, either the part that passes through the glass or the part that is reflected by the glass. By means of several lasers and corresponding photodiodes, several panes (either as loose samples or as fully installed windows) can be checked simultaneously as to whether there is condensed water on the surface or not. The system can operate in two modes; transmission or reflection mode. The reflection mode has the advantage that all the measurement equipment can be kept indoors, but the transmission mode gives a clearer result. It might also be easier to align the detection system for the transmission mode. The physical property that is measured is the visibility through the sample (window), which is also the most interesting parameter.