The Bluetooth-capable hot-wire anemometer testo 405i, in combination with a smartphone or tablet, is a compact measuring instrument for air flow velocities, temperatures and volume flows. Equipped with a telescopic shaft, extendable to 400 mm, it allows flexible applications in rooms and ducts. Via the App installed on the end device, users can comfortably read off their measurement values, configure volume flow measurements quickly and easily, and reliably determine timed and multi-point mean values. The measurement protocols can then be directly sent as PDF or Excel files. In combination with the Bluetooth thermal hygrometer testo 605i, the testo 405i is suitable for determining cooling or heating performance.