Manganin
Manganin is a trademarked name for an alloy of typically 86% copper, 12% manganese, and 2% 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.
History
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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".[3]
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. [4]
Properties
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Cu86/Mn12/Ni2 Electrical Properties Temperature coefficient ( K-1 ) 0.00001 Electrical resistivity ( µOhmcm ) 43-48 Mechanical Properties Elongation at break ( % ) <50 Izod impact strength ( J m-1 ) 107 Modulus of elasticity ( GPa ) 124-159 Tensile strength ( MPa ) 300-600 Physical Properties Density ( g cm-3 ) 8.4 Melting point ( C ) 960 Thermal Properties Coefficient of thermal expansion ( x10-6 K-1 ) 14-19 @ 20-100C Maximum use temperature in air ( C ) 300 Thermal conductivity ( W m-1 K-1 ) 22 @ 23C
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
References
- ^ Manganin spec. sheet
- ^ Stability of Double-Walled Manganin Resistors
- ^ https://archive.org/stream/chronologicalhis00natirich/chronologicalhis00natirich_djvu.txt A CHRONOLOGICAL HISTORY OF ELECTRICAL DEVELOPMENT FROM 600 B.C.; NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION; 155 EAST 44th STREET; NEW YORK 17, N. Y.; Copyright 1946; National Electrical Manufacturers Association; Excerpts from this book may be used without permission
- ^ https://archive.org/stream/measureforgreatn001419mbp/measureforgreatn001419mbp_djvu.txt A Measure for Greatness; A SHORT BIOGRAPHY OF EDWARD WESTON; by DAVID O. WOODBURY, A.B., B.S., M.S.; McGRAW-HILL BOOK COMPANY, INC.; New York, Toronto, London; 1949
- ^ Manganin spec. sheet
- ^ CRC Handbook 27th ed 1943 p.1875
- ^ CRC Handbook 27th ed 1943 p.2485