He invented two alloys, constantan and manganin. It was produced in Germany where it was renamed "Constantan". It was first developed by Edward Weston in 1892, improving upon his Constantan (1887). The Schmidt-Boelter has a plated constantan wire wrapped around an insulating chip. Constantan is also used for electrical resistance heating and thermocouples. In addition, constantan is characterized by good fatigue life and relatively high elongation capability. Constantan is also used to form thermocouples with wires made of iron, copper, or chromel.