| 摘要 |
PURPOSE:To improve the sensitivity of a sensor in a low concentration range by using one limit current type oxygen sensor which is usable for measurement in a normal concentration range and merely changing the polarities of electrodes. CONSTITUTION:The oxygen sensor 1 is constituted by providing electrodes 3 and 3 made of porous metallic films of platinum on both surfaces of an ion conductor plate 2 made of a solid-state electrolyte, and covering the top center part of the ion conductor plate 2 on the side of one electrode 3' with a cap- shaped cover 5 which has a small diffusion hole 4 and thus forming an insulated chamber R inside. Changeover switches 7 for polarity switching are connected between both electrodes 3 and 3' of this limit current type oxygen sensor 1 and a power source 6. When movable pieces 7a and 7a of the changeover switch 7 are switched to fixed pieces 7b and 7b, the sensor 1 is put in the measurement mode of the normal concentration range and when the switches are switched to the fixed pieces 7c and 7c, the polarities are inverted to place the sensor in the measurement mode of the low concentration range. |
