Constantan is a copper-nickel alloy primarily composed of 55% copper and 45% nickel. It is known for its stable electrical resistance over a wide range of temperatures, making it ideal for use in thermocouples and resistors. This alloy is often used in applications where precise temperature measurements are crucial, such as in thermometers and industrial sensors. Its resistance to corrosion and oxidation also contributes to its durability, allowing it to perform well in various environments.