You need to understand the measurement range and characteristics of commonly used temperature measuring instruments.
When talking about commonly used temperature measurement instruments, the ones that come to mind are definitely electric resistance thermometers and thermocouples. In fact, in addition to these two types, there are four or five types of temperature measurement instruments, which you all need to be familiar with.
The most familiar ones are thermal resistors, thermocouples and thermistors.
The characteristics of platinum thermal resistance and copper thermal resistance of thermal resistance temperature measuring instrument are its good accuracy and sensitivity and large temperature-receiving area, but it will be affected by the ambient temperature. The characteristics of thermocouples include many types. There are eight types of internationally standardized thermocouples. They are highly adaptable and simple in structure. Except for three precious metals, the rest are cheap metal thermocouples. They are cheap, widely practical, and will also affect the ambient temperature. Its temperature measurement is affected. The characteristics of the thermistor are that it is small in size and has fast response. It has high sensitivity but poor linearity and is also affected by the ambient temperature.
The accuracy of the copper-platinum thermal resistor can be 0.1-0.3. The temperature measurement range of the copper thermal resistor is smaller than that of the platinum thermal resistor. The former is only about -50-180℃, while the temperature measurement range of the platinum thermal resistor is about -200-600℃. The accuracy of the thermistor is within 0.3-0.5, which is less accurate than the thermal resistor. Except for 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.
Four other temperature measuring instruments
The bimetal thermometer has a simple structure, is easy to use, is resistant to vibration and impact, and is easy to maintain. It is especially suitable for temperature measurement in places with large vibrations. It can also be used as a temperature relay controller, extreme temperature signal or temperature compensation for a certain instrument.
Pressure thermometer can be used for temperature measurement in vibration or close range and radiation places. During use, be careful not to lay the capillary tube along the hot and cold pipes or the outer wall of the equipment.
Thermal expansion thermometers commonly used in the petrochemical industry are mercury thermometers, organic liquid glass thermometers and electrical contact mercury thermometers, which are usually used to obtain degree data on-site. However, it cannot withstand high pressure and is easily broken, explosive and flammable.
The last is the non-contact thermometer. Its characteristics are that it does not interfere with the temperature measurement site, responds quickly, and has a wide temperature measurement range. It is used in distributed temperature measurement situations that are susceptible to external interference and difficult to calibrate, such as radiation thermometers and optical thermometers. Thermometers, heat detectors, etc.
