electronic means for processing the electrical signal emitted by the temperature measuring element 2 to which means it is connected the measuring element 2 may be a thermocouple or a temperature measuring probe of the resistance type or the semiconductor type or any other type of probe in the case of the thermocouple this is formed by the weld of the ends of two wires made of different metals these wires being electrically insulated except at their welded ends these wires forming the electrical connection means 3 are protected by a sheath 4 except in the vicinity of the thermocouple the end 5 of the sheath 4 is welded to the bearing piece 6 so that the unprotected part of the electrical connection means 3 penetrates the channel 10 and so that the thermocouple 2 lies in the cavity 9 which emerges on the face 8 of the bearing piece 6 it being possible for the thermocouple 2 to be advantageously locked in position in the passage channel 10 by means of a locking screw the bridge 11 is welded to the wall 1 by means of the welds 13 the free space between the branches of the bridge 11 and the wall 1 forms a housing 14 for the bearing piece 6 the latter is fitted in its housing so that the face 8 equipped with the cavity 9 is in contact with the wall 1 whose temperature it is.