Resistive Metal Oxide Combined with Optical Gas Sensor in an Electro-optical Nose for Odour Monitoring

This paper describes a prototype of artificial olfactory system or electro-optical nose (NEONOSE) containing commercially available MOX and optical (NDIR) gas sensors, forming an array of a total of 13 sensors (six MOX and seven NDIR sensors). The advantage of this configuration is to combine non-specific (MOX) and specific (NDIR) sensors to obtain an orthogonal array of sensors with a wider spectrum of responses. All the electronic circuits have been designed for this application. The prototype consists of two boards (containing different type of sensors) with two microcontrollers that communicates each other by using a digital interface. The Main Board is responsible for collecting the measurements from all the sensors and transmitting them via Bluetooth to a Smartphone. All the sensors that transmit data via I2C bus, which are all the MOX sensors and one of the optical sensors, are located on this board (main). The Secondary Board contains other NDIR sensors and is responsible for processing and sending this data to the Main Board via SPI communication. All the sensors of the Secondary Board are NDIR type. Some of them return the values in analog format, requiring the use of operational amplifiers for signal processing and analog-to-digital converters for data generation. The pre-processed data of all the sensors are sent via Bluetooth to an Android smartphone, where they are collected and stored using an own-developed application. Some measurements with different industrial gases have been done for testing the device. Keywords: metal-oxide sensors (MOX), optical sensors, electronic nose, smartphone, gas sensors.