Abstract: Measuring cell for determining oxygen concentration in a combustion engine exhaust stream utilizes a wafer or disc of stabilized ZrO.sub.2 as a solid electrolyte. A pair of concentric metal tubes having oppositely directed flanges contact electrode surfaces on the wafer and provide rugged electrical connections thereto. A pair of tubular ceramic sleeves positioned between the metal tubes electrically insulate the metal tubes from each other, seal (with the help of high temperature ceramic fiber gaskets) the wafer from leakage of exhaust gases to the reference side of the cell and space the wafer from the outer metal housing. The ceramic sleeves also maintain high temperature sealing and contact pressure between the tube flanges and the electrodes by virtue of the fact that they have a greater longitudinal length subject to temperature expansion than does the metal housing, thus making up for the fact that their temperature expansion coefficient per unit of length is lower.