康铜是一种铜镍合金，由55%的铜和45%镍（Cu55Ni45）所组成，它的特性是不易随温度变化而改变其性质，且电阻率高。

Constantan, also known as Eureka, Advance and Ferry, is a copper-nickel alloy usually consisting of 55% copper and 45% nickel. Its main feature is its resistivity, which is constant over a wide range of temperatures. Other alloys with similarly low temperature coefficients are known, such as manganin (Cu₈₆Mn₁₂Ni₂).