Constantan

ρ = 4.9 ∙ 10-7 Ω · m (20 ° C) ρ = 5.1 ∙ 10-7 Ω · m ( 600 ° C)

Constantan is a brand name of ThyssenKrupp VDM GmbH for an alloy which generally consists of 55 % copper, 44 % nickel and 1% manganese. It is characterized by an over wide temperature ranges approximately constant electrical resistivity. There are other alloys with similarly low (eg, manganin, Cu86Mn12Ni2 ) or even lower temperature coefficients are known.

The brand name

The brand name was registered with the German Patent and Trademark Office on December 14, 1952 and has since gone on to refer to these copper -nickel alloy in the common parlance. In the English -speaking world the name is protected in the spelling of Constantan. Another brand name for a very similar alloy is Isotan of the Isabelle Heusler GmbH & Co KG.

Background and Use

The rather low temperature dependence of the electrical resistivity of constantan is almost exclusively due to the fact that this alloy has a wide temperature range, a high impurity concentration within their crystal structure. This means that, although depending the density of the impurity in the material by the temperature and increases slowly with increasing temperature, but mainly influence due to the large number of defects in the crystal structure of this electron - scattering in them, and not the well of the temperature dependent electron-electron or electron-phonon scattering. Similar properties are exhibited by the alloy Kanthal.

Because of the small temperature coefficient of constantan for precision and measuring resistors used. Also pushing and heating elements are made of constantan.