RTD temperature sensors have between two and four lead wires. These wires are insulated and connected to a resistance element, or the part that increases in resistance as the wires heat up. Copper, platinum, and nickel are all popular choices for the resistance element.
As the wires get hotter, they transfer heat to the resistance element. One of the basic laws of thermodynamics is that metals’ resistance to electricity increases as they warm up, a characteristic known as a positive temperature coefficient.
The external device calculates the substance’s temperature based on how resistant the metal has become, which involves converting Ohms to degrees Fahrenheit. This conversion formula varies based on the resistance element’s material and positive temperature coefficient.