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:
