Resistance alloy with moderate resistivity and low temperature coefficent of resistance with a flat resistance/temperature curve over a wider range than the "manganins". Constantan also shows better corrosion resistance than the manganins. Uses tend to be restricted to ac circuits. Constantan is also the negative element of the type J thermocouple with Iron being the positive; type J thermocouples are used in heat treating applications. Also, it is the negative element of the type T thermocouple with OFHC Copper the positive; type T thermocouples are used at cryogenic temperatures.