The thermal mass flowmeter measures air/gas flow using the principle of convective heat transfer. The system utilizes two resistance temperature detectors (RTDs); an integrated circuit heats one to serve as the flow sensor, while the second acts as a reference sensor to establish the baseline gas temperature. The instrument maintains a constant temperature differential between these two elements. As medium pass across the heated sensor, they carry heat away from it, causing a cooling effect and subsequent energy loss. This temperature variance generates a highly accurate signal directly proportional to the medium velocity; a greater temperature difference indicates a higher flow rate.