Manganin

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
A manganin resistor made in 1900 at the Bushy House physic laboratory.
TypeCopper-manganese alloy
Physical properties
Density (ρ)8.4 g/cm3
Mechanical properties
Tensile strength (σt)300–600 MPa
Elongation (ε) at break<50%
Izod impact strength107 J/m
Thermal properties
Melting temperature (Tm)1020 °C
Thermal conductivity (k) at 23 °C22 W/(m·K)
Linear thermal expansion coefficient (α)(14–19)×10−6 K−1
Specific heat capacity (c)0.097 cals/gm
Electrical properties
Volume resistivity (ρ)43–48 μΩ⋅cm
Source[1]

Manganin foil and wire is used in the manufacture of resistors, particularly ammeter shunts, because of its virtually zero temperature coefficient of resistance value[2] and long term stability. Several Manganin resistors served as the legal standard for the ohm in the United States from 1901 to 1990.[3] 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.[4]

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".[5] Five years later, after experimenting with alloys of copper, nickel, and manganese, he developed Manganin. In May 1893, Weston received a patent for the material and its use for resistors. While Manganin represented a significant advance in technology -- the material was a conductive metal with constant resistance over a wide range of working temperatures, Weston did not receive wide recognition at the time.[6]

Properties

Cu86/Mn12/Ni2

Electrical Properties

  • Temperature coefficient: 1.5×10−5 K−1

Mechanical Properties

  • Modulus of elasticity: 124–159 GPa
  • Maximum use temperature in air: 300 °C
Cu84/Mn12/Ni4[7]
Temperature [°C] coefficient of resistivity
 12 +.000006
 25  .000000
100 −.000042
250 −.000052
475  .000000
500 +.00011 
Resistance of Wires at 20 °C[8]
AWG ohms per cm ohms per ft
10 .000836  0.0255
12 .00133   0.0405
14 .00211   0.0644
16 .00336   0.102 
18 .00535   0.163 
20 .00850   0.259 
22 .0135    0.412 
24 .0215    0.655 
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   

References
  1. "Manganin 230 Shunt Wire". California Fine Wire Co. Retrieved 13 January 2018.
  2. "Goodfellow Technical Information Manganin® - Resistance Alloy". www.goodfellow.com. Retrieved 2016-09-11.
  3. "Stability of Double-Walled Manganin Resistors" (PDF). Archived from the original (PDF) on 2006-10-06. Retrieved 2007-04-30.
  4. "Special Use Sensors—Manganin Pressure Sensor" (2015) Data Sheet - Micro Measurements - Vishay Precision Group, Inc.
  5. National Electrical Manufacturers Association. A chronological history of electrical development from 600 B.C. New York, N.Y., National Electrical Manufacturers Association.
  6. Woodbury, David O. (1949). A Measure for Greatness; A Short Biography of Edward Weston. New York, Toronto, London: McGraw-Hill.
  7. CRC Handbook 27th ed. Feb 1943. p. 1875.
  8. CRC Handbook 27th ed. Feb 1943. p. 2485.
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