PRECISION (3 ZONE)FURNACES Similar to construction of tube furnaces, 3 zone precision furnaces are designed to give the operator a much wider stable heated (± 5 °C) length through seperate controlled zones applied to the same tube. Heated length is divided into three zones where power is controlled by means of seperate controllers. Thus not only a longer heated tube length is achieved but also to create a temperature gradient along the tube is possible.