The instrument for measuring air moisture, material equilibrium moisture and pressure dewpoint in compressed air systems. Up to 3 temperature or humidity probes can be displayed; data transmission is radio-controlled, i.e. wireless. Measurement data can be transmitted by infrared to the Testo printer. It is also possible, during cyclical printing, to print measurement data once every minute, for example. testo 635 immediately displays the dewpoint difference between ambient air and the wall surface when analysing moisture on walls and ceilings. There are precision probes up to -60°C tpd available to inspect pressure dewpoint in compressed air systems. The humidity sensor developed by Testo has proven itself world-wide and has outstanding features in terms of precision, long-term stability, temperature resistance and robustness.