The measurement range and characteristics of commonly used temperature measuring instruments need to be understood
When talking about commonly used temperature measuring instruments, the electric thermal resistance and thermocouple must come to mind. In fact, besides these two, there are four or five kinds of temperature measuring instruments. In fact, you must be familiar with them.
The most familiar ones are thermal resistance, thermocouple and thermistor
The characteristics of platinum thermal resistance and copper thermal resistance of thermal resistance thermometers are that they have good precision and sensitivity, and the temperature is large, but they will be affected by the ambient temperature. There are many types of thermocouples. There are eight types of international standard thermocouples, which are highly adaptable and simple in structure. Except for the three precious metals, the rest are cheap metals. Thermocouples are cheap, widely available, and the ambient temperature will also affect Its temperature measurement is affected. The characteristics of the thermistor, it is small in size and fast in response, high in sensitivity but poor in linearity, and is also affected by the ambient temperature.
The accuracy of copper-platinum thermal resistance can be 0.1-0.3, and the temperature measurement range of copper thermal resistance is smaller than that of platinum thermal resistance. The former is only about -50-180°C, while the temperature measurement range of platinum thermal resistance is about -200-600°C. The accuracy of the thermistor is within 0.3-0.5, which is worse than that of the thermal resistance. In addition to the S-type thermocouple, the accuracy of the other seven types of thermocouples is between 0.4-1.0, and the temperature measurement range is about -200-1100.
The other four temperature measuring instruments
Bimetallic thermometer, simple structure, easy to use, resistant to vibration and shock, easy to maintain, especially suitable for temperature measurement in places with large vibration, and can also be used as temperature relay controller, extreme temperature signal or temperature compensation of an instrument.
The pressure thermometer can be used for vibration or close-range temperature measurement and temperature measurement in radiation places. Be careful not to lay the capillary along the hot and cold pipes or the outer wall of the equipment during use.
Thermal expansion thermometers, commonly used in the petrochemical industry are mercury thermometers, organic liquid glass thermometers and electric contact mercury thermometers, which are usually used for on-site occasions to obtain degree data. However, it cannot withstand high pressure and is easily broken and explosive and flammable.
The last is the non-contact thermometer, which is characterized by no interference with the temperature measurement site and fast response, wide range of temperature measurement, and is used in occasions where distributed temperature measurement is easily affected by external interference and difficult to calibrate, such as radiation thermometers, optical thermometers, etc. Thermometers, heat detectors, etc.
