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Constantan Resistance Wire from Copper and Nickel
Besserwisser16 (Wikimedia Commons) · CC0
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13. Oktubre 2026NO
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Constantan Resistance Wire from Copper and Nickel

Constantan is a copper-nickel alloy, usually 55 % copper and 45 % nickel, whose electrical resistance stays nearly the same as it warms; that is why strain gauges, thermocouples and resistance coils are wound with it. Copper and nickel melt together in any proportion, so the alloy is made by fusing the two, casting small sticks and drawing them into wire. The melt follows C. Morfit's copper-nickel alloy as Brannt gives it in *The Metallic Alloys* (1889): nickel and an equal weight of copper fused with borax in a graphite crucible, the rest of the copper stirred in. Hiorns (1912) adds that the nickel must be as pure as possible, which is what the Mond process gives.
Abantado
Foundry day, then drawing

Mga Tagubilin

1

Weigh the charge

For 1 kg of 55/45 constantan weigh 450 g nickel and 550 g copper, and set aside 100 g of the copper for the second addition. Use nickel as pure as you can get: Hiorns warns that silicon, carbon, iron and sulphur in it greatly reduce how well the alloy works.

Mga materyales para sa hakbang na ito:

Lingote ng TansoLingote ng Tanso550 g
Nikel na carbonylNikel na carbonyl450 g

Mga kailangang kasangkapan:

Timbangang panimbangTimbangang panimbang
2

Fuse nickel with an equal weight of copper

Put the nickel and an equal weight of copper (450 g of each) into a graphite crucible with some borax, and fuse them in the furnace. This is Morfit's first stage: nickel melts far hotter than copper, and melting it among copper brings it down sooner. Constantan itself melts at about 1,220–1,300 °C.

Mga materyales para sa hakbang na ito:

Pulbos na boraksPulbos na boraks1 as required

Mga kailangang kasangkapan:

Krisol na grapito at luwadKrisol na grapito at luwad
Pugon na UlingPugon na Uling
Sipit ng KrisolSipit ng Krisol
Guwantes na Matibay sa InitGuwantes na Matibay sa Init
Delantal na KatadDelantal na Katad
3

Stir in the rest of the copper

Add the remaining 100 g of copper to the melted mass, stirring constantly with an iron rod until it has gone in and the metal is one even liquid.

Mga kailangang kasangkapan:

Patulis na panghalong bakalPatulis na panghalong bakal
Pugon na UlingPugon na Uling
Sipit ng KrisolSipit ng Krisol
Guwantes na Matibay sa InitGuwantes na Matibay sa Init
4

Cast small sticks

Pour the alloy into a warmed ingot mould as small sticks, as Morfit did. Pour in one run; the alloy chills quickly.

Mga kailangang kasangkapan:

Hulmahan ng lingoteHulmahan ng lingote
Sipit ng KrisolSipit ng Krisol
Guwantes na Matibay sa InitGuwantes na Matibay sa Init
Delantal na KatadDelantal na Katad
5

Anneal the sticks

Anneal the cast sticks before working them: cast copper-nickel is crystalline, and Hiorns gives careful annealing at a moderate temperature as the cure.

Mga kailangang kasangkapan:

Pugon ng pagpapalambotPugon ng pagpapalambot
Sipit ng KrisolSipit ng Krisol
Guwantes na Matibay sa InitGuwantes na Matibay sa Init
6

Draw it like copper wire

Forge a stick into a round rod, file a taper and draw it through the drawplate hole by hole, as copper wire is drawn. Never take the size down too fast: Hiorns warns that metal drawn without annealing breaks unless it rests five to ten minutes between passes. Anneal it as the copper wire is annealed. Simmons's strain gauges used No. 40 gauge, about 0.08 mm.
7

Measure the resistance

Measure the diameter in several places, cut a measured length and find its resistance on a Wheatstone bridge. Compare the result with the ohms per metre in the next step. A wire that reads much higher than expected has a thin place or a crack in it.

Mga kailangang kasangkapan:

MikrometroMikrometro
Tulay ni WheatstoneTulay ni Wheatstone
8

Charge and resistance figures

Naglo-load ng Jupyter notebook…
9

Troubleshooting

Constantan wire troubleshooting.

Flow

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10

History and honest limits

In 1887 Edward Weston found an alloy whose resistance falls as it warms, a property, he wrote, of no other metallic conductor he knew. Wikipedia says his "Alloy No. 2" was produced in Germany and renamed Konstantan. By 1912 Hiorns listed Constantan, Eureka and Heckenham metal among the copper-nickel alloys used for resistances. Morfit's alloy was 33 nickel to 67 copper; we keep his two-stage method and scale it to 55/45, the usual constantan and Simmons's wire. That scaling is ours. The 55/45 figure and the resistivity are from Wikipedia's Constantan article. Very fine wire like No. 40 gauge needs drawplate holes that fine.

Mga Materyales

3

Mga Kinakailangang Kasangkapan

11

Ang blueprint na ito ay gumagawa ng

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Kawad na constantan

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Kaugnay na Blueprint

Ang mga blueprint na ito ay nagbabahagi ng kaalaman — mga teknik, materyales, o prinsipyo

Carbonyl Nickel by the Mond Process: Mond, 1891
Mapanganib

Carbonyl Nickel by the Mond Process: Mond, 1891

ni PeterSE

Paggawa ng Metal

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