PURPOSE: To protect damage to electrodes from vibration while checking the conduction between electrode due to the attachment of carbon by fastening the electrodes in a through hole in an insulating retaining body while a gas detecting element is formed on the end of the retaining body like a film.
CONSTITUTION: A cylindrical retaining body 3 made of an electrically insulating ceramic such as Al2O3 is set as intact or after temporarily baked upto about 1,000°C. Then, a pair of electrodes 2a made of a platinum wire is inserted into a through hole 3a and the cylindrical retaining body 3 is baked upto about 1,500°C to fasten the electrodes 2a by shrinkage of the ceramic by baking. A slurry comprising a metal oxide such as titanium dioxide, tin oxide, zirconium oxide and the like, a binder and a plasticizer is applied on the end of the retaining body 3 by printing method or the like to fully cover the electrodes 2a projected from the end thereof 3 and then baked. With such an arrangement, the electrodes can be completely free from effect of any vibration and gas flow while the conduction between the electrodes due to the attachment of carbon can be checked as they are not exposed.
OOTA MINORU
KAWAKAMI TOMIO
YASUDA ETSUROU
