Konstantan

Konstantan, more commonly known as Constantan, is a copper–nickel alloy used for electrical resistors, thermocouple wires, and strain gauges. It typically contains about 55 percent copper and 45 percent nickel by weight, though exact compositions vary to tailor properties.

Key properties include a relatively high resistivity compared with copper and, most notably, a very low temperature coefficient of resistance at room temperature, making its resistance nearly invariant over moderate temperature changes. It is also ductile and offers good corrosion resistance in many environments.

Applications include precision resistors and resistance standards, where stable resistance is required, and strain gauges, where a predictable resistance change under strain is needed. In thermocouples, Constantan forms a thermoelectric pair with copper (Type T thermocouple), valued for a practical temperature range and stable emf response.

Manufacture involves alloying copper with nickel and subsequent annealing to homogenize the material. The name Constantan derives from its nearly constant resistance with temperature; the variant spelling Konstantan appears in some languages.