The measuring method of a bimetal thermometer is the expansion of two different metals. Those two inseparable jointed metal strips each have a different thermal expansion coefficient. The bimetal system is built in the stem of the thermometer and functions as a temperature sensor. The measuring method of an inert gas filled thermometer is the expansion of gas in a closed system. Changes in temperature of the process to be measured create a change of pressure in the measuring system, which is translated on the dial into read out of the correct temperature. This type of thermometer is available as direct mounting and as capillary thermometer.