Platinum thin film RTD
The thin film style of RTD is probably the most popular design because of their rugged design and low cost.
The thin film element is manufactured by coating a small ceramic chip with a very thin (.0001”) film of platinum and then laser cutting or chemical etching a resistance path in the platinum film.
The element is then coated with a thin layer of glass to protect it from harmful chemicals and gases.
Larger extension lead wires are spot welded to the chip and this junction is then covered with a drop of epoxy to help hold the wires to the element.