A sensor apparatus for analyzing a gas in a process chamber, having a housing, a gas sensor for analyzing at least a part of the gas, the gas sensor being arranged at a determined position in the housing, a gas feed for connecting the housing to the process chamber to feed the part of the gas from the process chamber into the housing and to the determined position, and a gas discharge for discharging the gas from the housing, wherein the gas feed and the gas discharge are configured as tubes lying inside one another, characterized by a closure cap at the combustion chamber-side end of the tubes lying inside one another, the closure cap including an even number of at least four openings with the same area, which are connected alternately as a gas inlet and a gas outlet to the tubes lying inside one another is provided.