Manganin is a trademarked name for an alloy of typically 84% copper, 12% manganese, and 4% nickel. It was first developed by Edward Weston in 1892, improving upon his Constantan (1887).

Manganin foil and wire is used in the manufacture of resistors, particularly ammeter shunts, because of its virtually zero temperature coefficient of resistance value^[1] and long term stability. Several Manganin resistors served as the legal standard for the ohm in the United States from 1901 to 1990.^[2] Manganin wire is also used as an electrical conductor in cryogenic systems, minimizing heat transfer between points which need electrical connections.

Manganin is also used in gauges for studies of high-pressure shock waves (such as those generated from the detonation of explosives) because it has low strain sensitivity but high hydrostatic pressure sensitivity.^[3]

History

In 1887 Edward Weston discovered that metals can have a negative temperature coefficient of resistance, inventing what he called his "Alloy No. 2." It was produced in Germany where it was renamed "Constantan".^[4]

In 1892 Weston had finally completed his discovery of an alloy of copper, nickel, and manganese prepared by a complicated series of heat-treatments. In May, 1893, he received a basic patent on the composition, manufacture, and use of the material for electrical resistors. Production was carried out in Germany, and it became known as "Manganin". The availability of a practical conductive metal with an extremely constant resistance over the range of ordinary temperatures was a great advance in electrical technology and equipment design, but Weston did not receive general recognition for this.^[5]

Properties

Cu86/Mn12/Ni2^[1]

Electrical Properties

• Temperature coefficient: 0.00001 K⁻¹
• Electrical resistivity: 43–48 μΩ⋅cm

Mechanical Properties

• Elongation at break: <50%
• Izod impact strength: 107 J/m
• Modulus of elasticity: 124–159 GPa
• Tensile strength: 300–600 MPa

Physical Properties

• Density: 8.4 g/cm³
• Melting point: 960 °C

Thermal Properties

• Coefficient of thermal expansion from 20-100 °C: 14-19×10⁻⁶ K⁻¹
• Maximum use temperature in air: 300 °C
• Thermal conductivity at 23 °C: 22 W/(m·K)

Cu84/Mn12/Ni4
Temperature coefficient of resistivity
TempDegC (Somerville 1910)
12   .000006
25   .000000
100  -.000042
250  -.000052
475   .000000
500   +.00011

Resistance of Wires - 20 deg C
Manganin Q = 44. x 10-6 ohm cm
Gage B&S / ohms per cm / ohms per ft
10 .000836 .0255
12 .00133 .0405 
14 .00211 .0644
16 .00336 .102 
18 .00535 .163 
20 .00850 .259
22 .0135 .412 
24 .0215 .655 
26 .0342 1.04  
27 .0431 1.31 
28 .0543 1.66 
30 .0864 2.63 
32 .137 4.19 
34 .218 6.66 
36 .347 10.6 
40 .878 26.8

• Isabellenhütte - 1889 Manganin