Stages of Development of an Electronic Nose: Correlation Results Using a Dynamic Dilution Olfactometer in Conjunction with Human Experts

The different measurement techniques employed for gas and odor assessments are usually expensive, complex and time-consuming. Moreover, using these tools individually does not provide exhaustive information about odors under analyses. Therefore, this paper presents the development of a simple and low-cost odorant data logger as the second stage of the development of an electronic nose, combined with a classical technique as dynamic threshold olfactometry. The odorant data logger allows the estimation of odor concentration and odor intensity ratio of 1-butanol vapors, and it able to measure ethanol vapors. This instrument mainly comprises two commercial MOS sensors and an ATMEGA32 microcontroller. The odorant data logger showed an appropriate response to analytes’ concentrations in parts per billion, detecting lower levels than reported by the sensors’ manufacturer. Calibration curves were successfully adjusted to power-law functions, and the determination coefficients, R², ranged from 93 to 99 %. An olfactometric analysis for 1-butanol vapors was performed, showing a suitable R2 of 95.8 %. In order to estimate the odor concentration with the odorant data logger, a correlation with olfactometric values was also obtained. The values of R2 were 97.9 % and 99.4 % for the TGS 2600 and TGS 2620 sensors, respectively. In addition, the odor intensity ratio was computed, as other estimated dimension of the odor. The results of this stage of the development are promising in terms of its future usage for several applications, which will be depending mainly on the sensors array and the processing tools.