Manganin is a trademarked name for an alloy of typically 84.2% copper, 12.1% manganese, and 3.7% 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 and long term stability. Several Manganin resistors served as the legal standard for the ohm in the United States from 1901 to 1990. 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.
History
Invention and early development
In the late 19th century, the American chemist Edward Weston sought to improve the accuracy of electrical measuring instruments. At the time, the resistance of most metals changed significantly with temperature, introducing errors in precision measurements. In 1887, Weston discovered that certain alloys could possess a negative temperature coefficient of resistance. He invented "Alloy No. 2", a copper-nickel alloy which was later produced in Germany under the name Constantan.
Continuing his research, Weston developed Manganin in 1892 as an improvement upon Constantan. While Constantan had a low temperature coefficient, Manganin offered a resistance value that was virtually constant near room temperature and possessed better long-term stability. In May 1893, Weston received U.S. Patent 497,482 for a "Shunt for Electric Light and Power Stations," which detailed the use of his new high-resistance alloys in precision applications.
Standardization
Manganin was rapidly adopted by the scientific community, particularly in Germany where the Physikalisch-Technische Reichsanstalt (PTR) conducted extensive research on its properties. In 1890, K. Feussner at the PTR developed the "Reichsanstalt-type" resistor, which utilized Manganin wire wound on a metal form.
Refinement at NBS
To address the stability issues of the Reichsanstalt design, James L. Thomas at the U.S. National Bureau of Standards (now NIST) developed an improved standard in 1933, known as the "Thomas-type" resistor. These standards used heavy Manganin wire that was annealed at high temperatures in a vacuum to remove internal stresses. Crucially, the resistor was hermetically sealed in a double-walled container to protect it from humidity and atmospheric effects. In 1990, the international standard for resistance was redefined based on the Quantum Hall effect, which provides an invariant quantum standard. Despite this, Manganin resistors remain widely used today as robust working standards and in high-precision ammeter shunts due to their proven reliability and low cost compared to quantum standards.
|-
! Temperature [°C]
! coefficient of resistivity
|-
| 12
| +0.000006
|-
| 25
| 0.000000
|-
| 100
| −0.000042
|-
| 250
| −0.000052
|-
| 475
| 0.000000
|-
| 500
| +0.00011
|}
{| class="wikitable" style="text-align: center"
|+ Resistance of Wires at
|-
! AWG
! [Ω/cm]
! [Ω/ft]
|-
| 10
| 0.000836
| 0.0255
|-
| 12
| 0.00133
| 0.0405
|-
| 14
| 0.00211
| 0.0644
|-
| 16
| 0.00336
| 0.102
|-
| 18
| 0.00535
| 0.163
|-
| 20
| 0.00850
| 0.259
|-
| 22
| 0.0135
| 0.412
|-
| 24
| 0.0215
| 0.655
|-
| 26
| 0.0342
| 1.04
|-
| 27
| 0.0431
| 1.31
|-
| 28
| 0.0543
| 1.66
|-
| 30
| 0.0864
| 2.63
|-
| 32
| 0.137
| 4.19
|-
| 34
| 0.218
| 6.66
|-
| 36
| 0.347
| 10.6
|-
| 40
| 0.878
| 26.8
|}
See also
- List of named alloys
References
External links
- Isabellenhütte – 1889 Manganin