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 useful in various applications, particularly in thermocouples and resistors. This alloy is often used in temperature measurement devices due to its predictable behavior when exposed to heat. Additionally, constantan is resistant to corrosion, which enhances its durability in different environments, making it a popular choice in both industrial and scientific settings.