فنون

الجمال والعناية

حِرَف

الثقافة والتاريخ

ترفيه

البيئة

الطعام والمشروبات

الهندسة العكسية

العلوم

رياضة

التقنية

الأجهزة القابلة للارتداء

Constantan Resistance Wire from Copper and Nickel

Besserwisser16 (Wikimedia Commons) · CC0

أنشأه

Forge

13. أكتوبر 2026

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.

متقدم

Foundry day, then drawing

التعليمات

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.

المواد لهذه الخطوة:

سبيكة نحاس550 غ

نيكل عملية الكربونيل450 غ

الأدوات المطلوبة:

ميزان ذو كفّتين

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.

المواد لهذه الخطوة:

مسحوق البوراكس1 as required

الأدوات المطلوبة:

بوتقة غرافيت وطين

فرن فحم

ملقط بوتقة

قفّازات مقاومة للحرارة

مئزر جلدي

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.

الأدوات المطلوبة:

محراك حديدي

فرن فحم

ملقط بوتقة

قفّازات مقاومة للحرارة

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.

الأدوات المطلوبة:

قالب صب السبائك

ملقط بوتقة

قفّازات مقاومة للحرارة

مئزر جلدي

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.

الأدوات المطلوبة:

فرن التلدين

ملقط بوتقة

قفّازات مقاومة للحرارة

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.

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.

الأدوات المطلوبة:

ميكرومتر

قنطرة ويتستون

Charge and resistance figures

جارٍ تحميل دفتر Jupyter…

Troubleshooting

Constantan wire troubleshooting.

Flow

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.