A total of 240 volunteer breath samples were collected in this experiment, including 120 diabetic samples and 120 non-diabetic samples. The volunteers' breath samples were taken in the morning when they had not eaten or exercised. Volunteers were asked to take deep breaths through a disposable suction nozzle into a 1 L Tedlar collection bag, with a one-way valve attached to the bag to prevent external air pollution. After the breath sample was collected, the collection bag was immediately sent to the electronic nose equipment for detection. The signals were processed by the electronic nose low-pass filter circuit and then collected by the data acquisition card. Finally, they were digitized and sent to the computer. The specific sample collection process is shown in Fig. 2. For each sample, we obtained a data matrix represented by 32 response curves, and each response curve had 60 s × 100 Hz = 6000 data points.
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Gas sample collection process.
