Figure 11.

The microphone signal in relation to the set SO₂ concentrations at a constant CO₂ concentration of 6 vol.-%, using pre-calibrated mass flow controllers to conduct these measurements in the laboratory. The detected microphone signals and the set SO₂ concentrations show a clear linear relation. An increase of the SO₂ concentration increases the corresponding microphone signal. This graph is used as a reference to estimate the measured SO₂ concentration from the detected microphone signal during the field test.