Thermometers achieve thermal balance through conduction or convection, so that the indicated value of the thermometer can directly represent the temperature of the measured object. Generally, the measurement accuracy is high. In a certain temperature measurement range, the thermometer can also measure the temperature distribution inside the object.
The upper limit of measurement is not limited by the temperature tolerance of temperature sensing elements, so there is no limit to the highest measurable temperature in principle. For the high temperature above 1800℃, the non-contact temperature measurement method is mainly used. With the development of infrared technology, radiation thermometry is gradually extended from visible light to infrared light, and it is applied to room temperature below 700℃ with high resolution.
Extended data:
With the increase of temperature, the length of the metal tube (material A) increases, while the length of the unexpanded steel bar (metal B) remains unchanged, so the linear expansion of the metal tube can be transferred due to the change of position. In turn, this linear expansion can be converted into an output signal.
When the temperature changes, the volumes of liquid and gas will change accordingly.
Various types of structures can convert this expansion change into position change, thus producing position change output (potentiometer, induced deviation, baffle, etc. ).
Baidu encyclopedia-temperature sensor