Temperature probe for U value measurement, triple sensor system

The U-value (formerly k-value) is the most important value used to rate the energy efficiency of building components. With the new Testo 635 measuring this value has never been easier.
Three temperature values are needed to determine the U-value: outer temperature, surface temperature of inner wall as well as indoor air temperature.
Using the new wireless probes, the outer temperature can be quickly and easily measured with the window closed. The probe is simply positioned outside and transmits readings by radio to the measuring instrument in the room.
With the new patented U-value probe the two other temperatures required are measured using one probe. To measure surface temperature, three wires from the U-value probe are attached to the inner wall using modelling clay. The air temperature is measured by a sensor on the probe plug.
As soon as the three temperatures required are transmitted to Testo 635, the instrument calculates the U-value and displays it immediately.