A sensor assembly is described. The sensor assembly includes a sensor body having an outwardly-extending flange, first and second spacers, and an integral two-part housing with first and second housing parts. The two-part housing includes an annular groove in which the outwardly-extending flange and the first and second spacers are received. Facing annular surfaces of the housing and the first and second spacers are in sliding contact with each other. Facing annular surfaces of the first and second spacers and the flange are in sliding contact with each other. The annular surfaces of the housing apply a compressive load to the flange by means of the first and second spacers to maintain a hermetic seal between the facing annular surfaces. The facing annular surfaces accommodate differential thermal expansion between the component parts of the sensor assembly if the sensor assembly is exposed to an environment with an elevated temperature.