The Testo 0636 9730 Humidity/Temperature Probe Head carries out both relative humidity and air temperature in indoor areas, including long-term measurements. The probe head is easy to attach to Testo's universal handle with Bluetooth or handle with cable (both sold separately). The probe head can be depended on for reliable measurement results, because it is equipped with a long-term stable humidity sensor. This sensor is traceable to international humidity standards, such as ILAC, PTB and NIST.