The dew point control switch HYGRASREG® TW is installed on cooling or cold-water piping, or on cooled surfaces. It reliably detects formation of condensation by means of its humidity and temperature sensor (no conductivity measurement) and thanks to its patented measuring method, the pro-dynamic cross convention (Patent No. DE 10 2012 015 726.6), an exact measurement result, with ⁄ without optional display.Dew point temperature is that temperature at which air reaches the state of saturation and water vapour starts to condensate. Facilitated by the measuring range of 0...100 % relative humidity of the TW-U and by the adjustable threshold value of 75...100 % relative humidity of the TW-W, it is possible for example to operate cooling ceilings so that the switching output of the dew point monitor, the DDC, is activated and then triggers a heater or other control elements thereby preventing the formation of dew before dew builds up on pipes or cooling ceilings of the property to be monitored.