The bimetallic material is composed of two materials with different thermal expansion coefficients. In 1912, an American youth named John Alby Spencer first created the idea of using bimetallic materials to make snap discs, and later established Spencer Temperature Controller Company.
 

In 1931, General Plate Company and Spencer Temperature Controller Company were merged and reorganized into Metal&Control Company. Later, it was acquired by Texas Instruments. In 1958, the original patent was published. At present, there are more than 100 manufacturers of temperature controllers with bimetal temperature sensing elements in the world. The main types are snap temperature controller and adjustable temperature controller.