Manganin | |
---|---|
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]
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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". [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]
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Electrical Properties
Mechanical Properties
Temperature [°C] | coefficient of resistivity |
---|---|
12 | +.000006 |
25 | .000000 |
100 | −.000042 |
250 | −.000052 |
475 | .000000 |
500 | +.00011 |
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 |
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements, or as sensing devices for heat, light, humidity, force, or chemical activity.
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature. Thermocouples are widely used as temperature sensors.
A thermistor is a semiconductor type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word thermistor is a portmanteau of thermal and resistor.
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is electrical conductance, measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm, while electrical conductance is measured in siemens (S).
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Fernico describes a family of metal alloys made primarily of iron, nickel and cobalt. The family includes Kovar, FerNiCo I, FerNiCo II, and Dumet. The name is made up of the chemical symbols of its constituent three elements. "Dumet" is a portmanteau of "dual" and "metal," because it is a heterogeneous alloy, usually fabricated in the form of a wire with an alloy core and a copper cladding. These alloys possess the properties of electrical conductivity, minimal oxidation and formation of porous surfaces at working temperatures of glass and thermal coefficients of expansion which match glass closely. These requirements allow the alloys to be used in glass seals, such that the seal does not crack, fracture or leak with changes in temperature.
Constantan, also known in various contexts as Eureka, Advance, and Ferry, refers to a copper-nickel alloy commonly used for its stable electrical resistance across a wide range of temperatures. It usually consists of 55% copper and 45% nickel. Its main feature is the low thermal variation of its resistivity, which is constant over a wide range of temperatures. Other alloys with similarly low temperature coefficients are known, such as manganin.
Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructions are also used. The RTD wire is a pure material, typically platinum (Pt), nickel (Ni), or copper (Cu). The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes.
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