What is the working principle of expansion type thermometer?

Expansion type temperature JiJi including bimetallic thermometer, pressure type thermometer, glass thermometer. We, respectively, to whom they work. The working principle of bimetallic thermometer is to put the two pieces of expansion coefficient difference is very big pieces of metal welded together. When the temperature changes, the difference is very big, caused the different expansion coefficient of expansion and contraction, the deformation of sheet metal bending. According to different deformation and produce different momentum, momentum to drive the connection shaft and the other end of the indicating needle, indicate the temperature. Pressure type thermometer is the use of gas, liquid or of low boiling point liquid as heat medium, which is the feature of thermal expansion coefficient is bigger, the material filling in bulb, capillary and spring tube sealing systems. Bulb as measurement, after the bags medium temperature by temperature effect, change the pressure inside the containment system, cause the change of curvature of spring tube, makes the spring tube displacement of the free end, through the connecting rod and actuator drive the pointer in the table indicates the corresponding temperature value on the card. Glass rod thermometer is the use of thermal fluid temperature measurements of the principle of thermal expansion. Glass rod thermometer not only depends on the value of the change of the thermal fluid volume, also by the glass rod thermometer glass temperature changes in the bubble volume, but due to thermal expansion coefficient of liquid is greater than the expansion coefficient of glass many times, so, in fact, this kind of thermometer is moving along the capillary by thermal fluid volume change and display the temperature value.