Optimal Design for Quantification of Gas Concentration Based Olfactory Stimulator

Abstract

The existing olfactory stimulator based on magnetic resonance measurement can provide different concentration of olfactory stimulation by adjusting the concentration of olfactory liquid. However, with the progress of the experiment, it is difficult to ensure the concentration stability of odorant gas delivered to the nasal cavity, due to the odorant volatilization and the change of experimental environments (temperature, humidity, air flow), thus affecting the experimental accuracy. In this research, we improved the olfactory stimulation device previously developed by our laboratory to achieve accurate quantification of gas concentration. The improved olfactory stimulator mainly consists of three parts: control system, feedback system and pneumatic system. The control system is mainly use to control gas delivery and adjust concentration of olfactory gas. The feedback system is responsible for measuring the gas concentration. In the pneumatic system, an activated carbon device is added to the original foundation to reduce interference of irrelevant factors. After the improvement, the switching response time between different pneumatic branches reached to 75.2 ms, which is nearly 1 s less than the original device, and effectively improves the accuracy of stimulus. The experimental results show that the olfactory gas concentration of ethanol, pyridine and amyl acetate decrease by 6.7%, 71.4%, and 79.2% respectively, within 300 s before adjusting the gas concentration. The odorant gas concentration changes significantly in a short time. The gas concentration regulation function can be realized by adjusting the voltage of air pump of the feedback system to change the ratio of odorant airflow and pure airflow. When the gas concentration drops to 90% of the target value, it took 13 s to adjust the odorant gas concentration to the target value for pyridine and amyl acetate.

Keywords

• olfactory stimulator
• gas concentration quantification
• feedback regulation
• pid gas concentration sensor