Identifying natural and artificial odours through noise analysis with a sampling-and-hold electronic nose

A sampling-and-hold type electronic nose was used to investigate “frozen” sensor dynamics. The sensor was heated to the sensing temperature and exposed to a chemical environment for a short time. Then, while keeping the sensor in the chemical environment, the heating was switched off so that the sensor cooled down to room temperature. Chemicals species become trapped in the sensor film, and therefore, the current transport in the film is changed. The trapped chemicals are usually located at grain boundaries, and they influence the charge transport in the grains and between the grains. This gives random fluctuations to the local conductivity. Resistance noise was employed to extract chemical information from the sensor in the cold state.