PREPARATION OF FILTER FOR GAS DETECTION ELEMENT

摘要

PURPOSE:To obtain a filter for removing the substance obstructing the detection capacity of the gas sensor of a gas detection element, by molding and baking the precipitate formed by adding an alkali solution to a solution containing an aluminum salt and a zinc salt. CONSTITUTION:A gas sensor 3, a coil shaped heater 4 and an explosion-proof net 5 are respectively arranged to a substrate 2 equipped with four electrode pins 1 and a cup shaped filter 6 is connected to the substrate 2 by an epoxy adhesive. The filter 6 is formed by a method wherein the ratio of the zinc salt and the aluminum salt in the solution containing both salts is adjusted so as to contain activated zinc oxide in an amount of 3-30% by wt. of activated alumina in the obtained filter and an alkali solution is subsequently added to said solution to adjust the pH of the solution mixture to 5-9 and the formed precipitate is molded and baked. Thus formed filter can adsorb and remove SO2 and H2S being poisoning substances and remove the obstructing detection capacity.