The differential pressure gauge testo 510i, in combination with a smartphone or tablet, is suitable for measurements of gas flow and static pressure, pressure drops on ventilators and filters, and for pressure-drop tests on gas pipes. In addition to this, the compact measuring instrument can be used for determining air flow velocity and volume flow. Via the testo Smart Probes 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 App also includes a measurement menu for the pressure-drop test including alarm. All measurement data can be presented either as a diagram or in tabular form. The measurement protocols can then be directly sent as PDF or Excel files.