Manganin

Manganin
A manganin resistor made in 1900 at the Bushy House physics laboratory.
Material type	Copper-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 strength	107 J/m
Thermal properties
Melting temperature (Tm)	1020 °C
Thermal conductivity (k) at 23 °C	22 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 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^[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]