A sensor assembly (2; 40; 50; 60) comprising: a sensor body (4; 62) having an outwardly-extending flange (10; 64) with a first annular surface (10a; 64a) and a second annular surface (10b; 64b); a first electrically non-conductive annular spacer that substantially surrounds the sensor body (4; 62) and has a first annular surface, a second annular surface, and an opening through which the sensor body (4; 62) is received; a second electrically non-conductive annular spacer that substantially surrounds the sensor body (4; 62) and has a first annular surface, a second annular surface, and an opening through which the sensor body (4; 62) is received; and a housing (12, 20) having an annular groove in which the outwardly-extending flange (10; 64) and the first and second spacers (22, 24) are received, the annular groove being defined between a first annular surface and a second annular surface of the housing (12, 20); wherein: the first annular surface of the housing is in sliding contact with the first annular surface of the first spacer; the second annular surface of the first spacer is in sliding contact with the first annular surface (10a; 64a) of the outwardly-extending flange (10; 64); the second annular surface (10b; 64b) of the outwardly-extending flange (10; 64) is in sliding contact with the first annular surface of the second spacer; and the second annular surface of the second spacer is in sliding contact with the second annular surface of the housing (12, 20); and wherein the first and second annular surfaces (12b, 20a) of the housing (12, 20) apply a compressive load to the outwardly-extending flange (10; 64) by means of the first and second spacers (22, 24) to provide a hermetic seal between the annular surfaces that are in sliding contact, and differential thermal expansion between the sensor body (4; 62) and the housing (12, 20) is accommodated by the sliding contact between the annular surfaces. a sensor body (4; 62) having an outwardly-extending flange (10; 64) with a first annular surface (10a; 64a) and a second annular surface (10b; 64b); a first electrically non-conductive annular spacer that substantially surrounds the sensor body (4; 62) and has a first annular surface, a second annular surface, and an opening through which the sensor body (4; 62) is received; a second electrically non-conductive annular spacer that substantially surrounds the sensor body (4; 62) and has a first annular surface, a second annular surface, and an opening through which the sensor body (4; 62) is received; and a housing (12, 20) having an annular groove in which the outwardly-extending flange (10; 64) and the first and second spacers (22, 24) are received, the annular groove being defined between a first annular surface and a second annular surface of the housing (12, 20); wherein: the first annular surface of the housing is in sliding contact with the first annular surface of the first spacer; the second annular surface of the first spacer is in sliding contact with the first annular surface (10a; 64a) of the outwardly-extending flange (10; 64); the second annular surface (10b; 64b) of the outwardly-extending flange (10; 64) is in sliding contact with the first annular surface of the second spacer; and the second annular surface of the second spacer is in sliding contact with the second annular surface of the housing (12, 20); and the first annular surface of the housing is in sliding contact with the first annular surface of the first spacer; the second annular surface of the first spacer is in sliding contact with the first annular surface (10a; 64a) of the outwardly-extending flange (10; 64); the second annular surface (10b; 64b) of the outwardly-extending flange (10; 64) is in sliding contact with the first annular surface of the second spacer; and the second annular surface of the second spacer is in sliding contact with the second annular surface of the housing (12, 20); and wherein the first and second annular surfaces (12b, 20a) of the housing (12, 20) apply a compressive load to the outwardly-extending flange (10; 64) by means of the first and second spacers (22, 24) to provide a hermetic seal between the annular surfaces that are in sliding contact, and differential thermal expansion between the sensor body (4; 62) and the housing (12, 20) is accommodated by the sliding contact between the annular surfaces.