Constantan is a copper-nickel alloy also known as Eureka, Advance, and Ferry.It usually consists of 55% copper and 45% nickel. Its main feature is its resistivity, which is constant over a wide range of temperatures. Other alloys with similarly low temperature coefficients are known, such as manganin(Cu86Mn12Ni2).
The alloy is non-magnetic. It is used for electrical regenerator's variable resistor and the strain resistor,
potentiometers, heating wires, heating cables and mats. Ribbons are used for heating of bimetals. Another field of application is manufacturing of thermocouples because it develops a high electromotive force (EMF) in association with others metals.
Copper nickel alloy series:Constantan CuNi40 (6J40), CuNi1, CuNi2, CuNi6, CuNi8, CuNi10, CuNi14, CuNi19, CuNi23,CuNi30, CuNi34, CuNi44.
Very importantly, constantan can be processed for self-temperature compensation to match a wide range of test material coefficient of thermal expansion. A-alloy is supplied in self-temperature-compensation (S-T-C) numbers 00, 03, 05, 06, 09, 13, 15, 18, 30, 40 and 50, for use on test materials with corresponding thermal expansion coefficients, expressed in parts per million by length (or µm/m) per degrees Celsius or kelvins
For the measurement of very large strains, 5% (50 000 microstrain) or above, annealed constantan (P alloy) is the grid material normally selected. Constantan in this form is very ductible; and, in gauge lengths of 0.125 inches (3.2 mm) and longer, can be strained to >20%. It should be borne in mind, however, that under high cyclic strains the P alloy will exhibit some permanent resistivity change with each cycle, and cause a corresponding zero shift in the strain gauge. Because of this characteristic, and the tendency for premature grid failure with repeated straining, P alloy is not ordinarily recommended for cyclic strain applications. P alloy is available with S-T-C numbers of 08 and 40 for use on metals and plastics, respectively.
Size dimension range:
Wire: 0.1-10mm
Ribbons: 0.05*0.2-2.0*6.0mm
Strip: 0.05*5.0-5.0*250mm
Main properties
| Property | Value |
| Electrical resistivity at room temperature | 4.9×10−7 Ω·m |
| Temperature coefficient at 20 °C | 8 ppmK−1 |
| Temperature coefficient −55 to 105 °C | ±40 ppmK−1 |
| Curie point | 35 K |
| Density | 8.9 × 103 kg/m³ |
| Melting point | 1221–1300 °C |
| Specific heat capacity | 0.39 kJ/(kg·K) |
| Thermal conductivity at 23 °C | 19.5 W/(m.K) |
| Linear coefficient of thermal expansion at 25 to 105 °C | 14.9×10−6 K−1 |
| Tensile Strength | 455–860 MPa |
| Elongation at fracture | <45% |
| Elastic modulus | 162 GPa |
Application of Resistor as below:
