Abstract : This work joins in the continuance of two theses presented by E. Fascetta in 1993 and C. Pupier in 1999 which were dedicated to the study of an original potentiometric gas sensor. Contrary to the classical potentiometric gas sensors, this one is made with two different electrodes set in the same gas atmosphere. These works gave place to important technological developments and allowed to propose the bases of an electrochemical model able to better interpret the influence of gases such as the oxygen on the sensor response. Our work thus consisted to better study the phenomena that are at the origin of the electrical response of this sensor and to optimize its functioning for various applications. The first part of this work concerns the physico-chemical characterization of the species that intervene in the creation of the electrical signal and in particular the study of the exact role of the oxygen. For that purpose, we used techniques usually employed for the study of the gas-solid interactions such as calorimetry and surface-potential measurements. Then, we studied the importance of the choice of materials used as well as influences of characteristic parameters such as the nature and the size of electrodes on the electrical response of the sensor. All these results were then used to propose an electrochemical mechanism allowing better understanding of the phenomena that give rise to the electric signal. This model was confronted with the experimental results concerning the influence of the oxygen pressure and the temperature, then it was extent to the action combined by the temperature, the pressure of oxygen and a reducing gas : carbon monoxide.