Fast, accurate location of leaks
The HG4 pulse generator emits pulses with a voltage of 40V which are conducted onto the roof structure. Since most roofs are connected to earth and the pulse generator is also earthed via the mains cable (earth plug), only the +terminal on the detector is connected to earth jack, while the -terminal is connected up to a ring circuit laid out on the roof surface. In this way the roof (concrete, corrugated metal etc.) becomes the +terminal and the ring circuit is the -terminal. Since all roof coverings are more or less non-conducting, the electrical pulse chooses a path across the moisture to where the leak is located and then flows over the damp roof in all directions to reach the ring circuit. Using the HG4 receiver we now determine the current´s direction of flow and trace it back to its source. This source is exactly the spot where moisture is penetrating the roof covering. For this operation the roof must allways be damp, but it makes no difference whatsoever if the moisture is unevenly distributed. Gravel or earth coverings with paving stones or roof-gardens present no obstacle to the detector which will even operate through a layer of nonreinforced concrete above the damp-proofing.
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