These units have a maximum operating temperature of 1200°C, 1500°C and 1600°C.

For units at 1200°C, heating is via an integral resistance wire element wound on to the ceramic work tube which is an integral part of the furnace. At 1500°C and 1600°C, silicon carbide rod elements are mounted parallel to the tube.

The end zone controllers are coupled to a centre zone thermocouple enabling the centre zone temperatures to be closely linked. This system provides a longer uniform zone temperature than that achieved by the use of single zone furnace of the same length.

Temperature uniformity

Temperature variation within the uniform zone is typically +5°C, with a significant proportion of the uniform zone length within 
+1°C. To improve the uniform zone length within a tube furnace, it is necessary to use multi-zone furnaces; the usual configuration is 3 zones.

Temperature uniformity is dependent on the tube diameter and heated length.