6J40
Constantan Wire (6J40 / Cu55Ni45)
A copper-nickel alloy with a resistivity that barely moves with temperature — roughly 0.49 µΩ·m at room temperature, and a coefficient close to zero. …
Product family
Constantan Wire
Roughly 0.49 µΩ·m and almost no temperature coefficient. The alloy behind most shunts, most wire-wound resistors, and the negative leg of three thermocouple types.
0.018–6.00Diameter, mm
1 kgMinimum order
3–7 dLead time
100 gSample at cost
| Property | Value |
|---|---|
| Resistivity, 20 °C | ≈ 0.49 µΩ·m |
| Temperature coefficient | ≈ ±20 ppm/K |
| Density | 8.90 g/cm³ |
| Max service in air | ≈ 400 °C |
| Diameter range | 0.05 – 6.00 mm |
Constantan's value is flatness. A shunt made from it holds its value as the enclosure warms; a thermocouple made from it produces a stable EMF against copper. It also solders easily, which matters more in instrument assembly than most datasheets admit.
The three things it is bought for
- Shunt and current-sampling resistors
- Precision wire-wound resistors
- Negative leg of type E, J and T thermocouples
Pairing
For thermocouple orders we draw the constantan leg from the same melt as the positive leg and ship them together. That single fact removes a pairing step from the customer's bench — and a source of error from his calibration.
Grades in this family
Pick the designation your drawing cites
Questions we get asked
Constantan or manganin?
Constantan for higher resistivity, easier soldering and most shunts. Manganin where the lowest possible temperature coefficient is the deciding factor. If you are unsure, send the resistance value and the operating temperature range.
Is 6J40 exactly Cu55Ni45?
It is the Chinese designation for the same alloy family. Contractual composition is fixed on the order and stated on the inspection report.
Send the specification — diameter, grade, temper, quantity.
We come back with a confirmed lead time and the documentation we can issue for the shipment. 100 g sample at cost; orders from 1 kg.
Request a quotation Order a 100 g sample