Gas sensors and signal processing
A recently completed project funded by the EU's Industrial Materials and Technologies (BRITE-EURAM) programme aimed to develop gas sensors, and associated signal processing mechanisms for the selective detection of CO2 and NOx in motor vehicle applications. The findings of this project will also have potential for use in other fields, such as the urban environment, industrial hygiene and safety. The ECONOX project, which began in 1994, was completed at the end of 1997. Sensors for the monitoring of gases are useful in several fields of application: - Inside a car, where if necessary the sensor could close shutters and turn on filters; - Inside the home, where the smell of burning or the risk of a gas explosion can be detected; - For engine manufacturers to monitor fumes from car exhausts more accurately. By the end of the project, some 50 sensors had been developed, with high performance ratings in terms of selectivity, reversibility and response time. Signal processing techniques were developed using various tests. Electronic circuits for operating the sensor (electrical supply, measurement and control of heating, and gas measurements) have also been developed. Two further systems were also examined, one for the car interior and the other for the exhaust. For the former, the sensor has been shown to be effective in air conditioning systems, reducing pollution. Measurements taken, in particular, while going through a motorway tunnel showed that CO2 concentration inside the car remained at a few parts per million, although levels outside were three to five times as high. For the exhaust fume application, the sensor was placed in a probe. The findings are very promising, with a good correlation between the signals produced by the ECONOX detector, engine speed (a diesel engine in this case) and the oxygen sensor. The work done within the ECONOX project is now being continued under a new project (BE97-4028), also funded by BRITE-EURAM, which aims to demonstrate the ability of the sensor to perform gas analysis for engine exhaust gas systems, and its potential in some engine applications (diesel and gasoline). This project will define conditions for mass production of the sensor, develop a prototype industrial device, and evaluate its operation in typical conditions for automotive applications. On the basis of prototype trials, it will improve and condition the sensor to meet durability and ageing criteria, with the goal of defining an operational device for automotive applications (NOx and HC)