Connected to the testo 635 humidity and temperature measuring device, the robust humidity probe measures relative humidity and temperature in storage, cooling, and working environments, as well as in climate and ventilation ducts. Additionally, a material compensation humidity measurement can be performed. To do this, the function for calculating the H2O content in the measuring device must be activated, and the material of the object to be measured must be set (anhydrite flowing screed, cement flowing screed, sand-lime brick, concrete, highly insulating brick, solid brick, hardwood, softwood, aerated concrete, particle board). The probe can also be connected to the testo 435-2 and testo 435-4 measuring devices, but without the ability to measure material compensation humidity.