Abstract: An improved heat shield for shielding a sheathed thermocouple from heat radiating from or to surrounding bodies having temperatures different from the temperatures of hot gases which are being measured by the thermocouple. The improved shield generally is comprised of two elements, namely, (1) an elongated refractory member having an axially extending central passage for receiving the thermocouple and a plurality of parallel passages surrounding the central passage and (2) a flanged tubular holder for attaching the refractory member to one end of a water cooled probe. The refractory member is constructed of a large diameter thin wall refractory tube which is bonded to the flanged holder and houses a plurality of small diameter thin walled refractory tubes which are bonded to the inner surface of the large tube. The tubes collectively and individually define the central and parallel passages.

Abstract: A thermocouple for measuring the temperatures of hot gases up to and above 3000.degree. F. with surroundings at the same or different temperatures, the thermocouple having its hot junction encased in a protective sheath which is detachably sealingly connected to the hot end of an elongated tubular housing containing thermocouple leads insulated both atmospherically and electrically. These leads extend back through the length of the housing and pass through an insulative sealing bushing disposed in the cold end of the housing for connection to a suitable recording instrument. The interior chamber defined by the sheath, housing and bushing is pressurized to assure that the interior chamber is atmospherically insulated and to prevent the hot gases from penetrating into the interior chamber and, together with effects of condensation, deteriorating the hot junction and the leads of the thermocouple and/or creating short circuits.