The compact instrument with built-in humidity probe head for measuring air moisture and temperature. The large 2 line display shows humidity, wet bulb temperature or dewpoint as well as temperature. When measuring at hard-to-access points, the humidity probe head can be easily removed and attached to the handle via the probe cable (accessory). Alternatively, the readings can be transmitted wirelessly over wide distances from the probe to the measuring instrument. To do this, the humidity probe head is attached to the radio handle (accessory) and the radio module (accessory) is added to testo 625.