Circuit Development Of Odor Detection System Based On Multi-sensor Array

As living standards improve, people’s requirements in living environment are increased and gradually realize the impact of the odor of their own quality of life. Malodor as an environmental pollution, is characterized by a person’s sense of smell and subjective feeling. This paper proposes a method of detection of odorous gases based on the olfactory identified and developed the circuit of this malodorous gas detection systems.Malodorous gases have wide range and volatile composition ratio. A single sensor is difficult to fully express Malodor gas concentration. Therefore, the system uses Malodor gas detection method based on multi-sensor array. Multi-sensor have a set of response fingerprint to composite malodorous gases. Calibration is done comparing the response of fingerprint groups with artificial olfactory discernible result, resulting of the calibration curve of the current measurement of the ambient gas. When measuring again, a fingerprint group of sensors in response to gas is compared with the given curve to obtain Malodor gas values. As long as there is sufficient noise ratio of response fingerprint of sensors, any odorous gases can be detected Malodor value.Considering system requirements, upper and lower machine is selected as the method to achieve system. Lower machine collected the gas signal and sent them to the upper computer to make storage and processing. The main task of this paper is to get a response fingerprint of sensors. Signal is acquired by acquisition circuit to get signal with higher noise ratio, which is provided for the calibration of the measurement system.Issues had a in-depth understanding of the working principle and operating characteristics of the sensors and designed corresponding preamp circuit to signal acquisition. Signal conditioning circuit takes advantage of C8050F020 microcontroller which is integrated A/D conversion and D/A conversion subsystems. Using the D/A conversion subsystem can automatically adjust zero for the initial of the sensor, achieving digital zero modulation. C8050F020 microcontroller comes within two DAC, which should be shared for multi-sensor array when adjusting zero. Using integrated systems can avoid the accumulation of noise in the signal transmission process, which can improve the signal to noise ratio.In addition to signal acquisition circuit which ensured the signal to noise ratio, some other circuits are needed to allow the system to work properly, including the design of pneumatic and realization of control circuits.After the completion of the circuit development,the circuit are verified through experiment. Signal response model is established based on sensor characteristics. Experiments are collecting malodorous gases to get the actual signal response curve, which is contrasted with the response model to get validated results. Experiments show that circuit developed of system meets the requirements and the response to gas is good.