IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 9, Issue 5 Ver. III (Sep – Oct. 2014), PP 45-49 www.iosrjournals.org www.iosrjournals.org 45 | Page Design of a Low Cost Instrumentation System for Oxygen Sensing Using Polyaniline/Cerium Oxide Composites Khened B.S 1 , Nagabhushana Katte 2 , M V N Pradeep 3 , M V N Ambika Prasad 4 , and M Sasikala 5 1 Department of Electrical and Electronics Engineering, BITM, Bellary-583 104, KA, India 2 Department of Electronics and Communication Engineering, BITM, Bellary-583 104, KA, India 3 Department of Instrumentation and Control, M I T,Manipal-576104,KA,India 4 Department of Materials science, Gulbarga University, Gulbarga-585 105, KA, India 5 Netaji Institute Of Engineering and Technology, Toopranpet(Vill), 508252 Nalgonda (Dist). AP,INDIA Abstract: In the present paper design and development of a low cost gas sensing system with Polyaniline/ Cerium oxide composite as sensing element is presented. Polyaniline / Cerium oxide composites are prepared by insitu polymerization. The composites are pressed in the form of pellets and are used as the sensing elements. The sensing element is interfaced with front end signal conditioning circuit, and ARM processor for data logging. The sensor readout circuit is based on resistance to voltage conversion technique. The performance of the system was tested for oxygen sensing application. Keywords: Polyaniline/ Cerium oxide composite, oxygen sensing, signal conditioning, ARM processor, resistance measurement. I. Introduction Need for monitoring and maintaining the pollutant gases in the environment within a specified limit has led to substantial research in the field of gas sensors. Several studies have been reported in the literature for detection of various gases using metal oxide sensors [1-11]. Huge number of gas sensors are commercially available in the market which employ metal oxides.However,these sensors operate at high temperatures and their electrical conductivity depends on the concentration of ambient gas. Since conducting polymer sensors have short response time, high sensitivity and are operated at room temperature, researchers have paid much attention on these novel materials for gas sensing applications. Polyaniline has gained importance in gas sensing applications due to its environmental stability, good conductivity and gas sensing ability. Gas sensing properties of conducting polyaniline composites and polypyrrole composites for various oxidizing and reducing gases have been extensively studied and detailed mechanism has been reported [12-20]. When the conducting polymer composites are exposed to the oxidizing or reducing gases, the conductivity of these sensing elements will change. The overall conduction in a sensor element is determined by various factors such as nature of dopant in polyaniline, surface reactions, resulting charge transfer processes with the underlying semi conducting material, transport mechanism through the sensing material, and morphology of sensing layer [21]. Since these sensors are operated at room temperature, the sensor resistance (R SENS ) is given by the following equation, R SENS = R AIR + ∆R GAS Where R AIR is the sensor resistance in air at room temperature and ∆R GAS is the variation in sensor resistance due to interaction between sensor element and the gas. The value of R AIR depends on method of preparation of sensing element, dopant and its concentration. The value of ∆R GAS depends on the gas concentration. In the present paper, the development of a low cost sensor system with Polyaniline/ Cerium oxide composite as sensing element and its interfacing with front end signal conditioning circuit is presented. The system is tested for oxygen sensing application. II. Sample Preparation Polyaniline/Cerium oxide composites were prepared by insitu polymerization. Aniline solution was formed by dissolving aniline (0.1mol) in 1M HCl. Cerium oxide was added to the aniline solution with vigorous stirring to keep Cerium oxide suspended in the solution. 0.1M Ammonium persulfate, which acted as the oxidant, was added to this reaction mixture slowly with continuous stirring at 0–5°C. The reaction mixture was kept stirring for 24 hours. The polymer which was in the form of greenish-black precipitate was recovered by vacuum filtration and washed with deionized water. To achieve a constant weight the precipitate was dried for 24 hours in an oven. In this way polyaniline – Cerium oxide composites with 5 different weight % of CeO 2 (10, 20, 30, 40, 50) in polyaniline were synthesized. The composites thus formed were characterized by Fourier Transform Infra Red Spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM),