Classification
Thermometers can be divided into expansion thermometer, pressure thermometer, thermocouple and RTD thermometer, radiation thermometer and other five types.
Expansion of the use of objects thermometer expansion and contraction of the performance of the expansion, liquid expansion and solid expansion of the two categories. Liquid expansion thermometer, depending on the filling of the working fluid is divided into mercury thermometer and organic liquid thermometer. Mercury glass tube liquid thermometer is the earliest and most commonly used thermometer. Due to mercury pollution, it has been eliminated. Solid thermometer (also known as mechanical thermometer) is divided into bimetallic thermometer and rod thermometer. Mechanical thermometers are used to measure temperature and are used as signal mechanisms for temperature compensators and automatic temperature regulators. Pressure thermometers measure the temperature indirectly based on changes in the volume of the enclosed working substance as the temperature changes, causing pressure changes. Pressure thermometer structure is simple, vibration-resistant, explosion-proof, easy to send and so on. Measurable -50 ℃ - +550 ℃, widely used in engineering surveying, a liquid pressure thermometer, gas pressure thermometer and steam pressure thermometer. Thermocouple thermometer is the use of thermoelectric effect to measure temperature. With high accuracy, wide measuring range (up to 180-1600 ℃) for long-distance transmission and automatic recording features. Thermistor thermometer is the use of conductors and semiconductor temperature is not the same when there is a different change in resistance to indirectly measure the temperature. With high precision, easy to distance measurement, multi-point measurement. Wide range of measurement is generally -120- +500 ℃ (in special cases up to -200-1000 ℃) than the thermocouple thermometer suitable for measuring low temperature, but the sensitivity is worse than the thermocouple thermometer. Thermocouples and RTD thermometers are also used as temperature sensors. Radiation thermometer is based on the role of objects made of radiation, with thermal elements not in contact with the media, the measured medium does not have to reach the same temperature, high measurement limit, commonly known as the pyrometer.
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