Elaborate on the difference between PT100 platinum resistance and K-type thermocouple

What is PT100?

(1) PT100 is a platinum thermistor, and its resistance value is proportional to changes in temperature. The relationship between the resistance of PT100 and temperature change is: when the temperature of PT100 is 0 ℃, its resistance is 100 ohms, and at 100 ℃, its resistance is about 138.5 ohms. Its industrial principle: When PT100 is at 0 degrees Celsius, its resistance is 100 ohms, and its resistance will increase uniformly with the temperature.

(2) PT100 is a commonly used temperature detection instrument in the medium and low temperature range for platinum thermistors. Thermal resistance temperature measurement is based on the characteristic that the resistance value of metal conductors increases with temperature.

(3) Its main features are high measurement accuracy and stable performance. The measurement accuracy of platinum resistance thermometer is very high, and it is not only widely used in industrial temperature measurement, but also made into a standard reference instrument.

The significant difference between the selection of PT100 platinum resistance and K-type thermocouple lies in the choice of temperature range. Thermistor is a temperature sensor used to measure low temperatures, typically ranging from -200 to 800 ℃, while K-type thermocouple is a temperature sensor used to measure medium to high temperatures, typically ranging from 400 to 1800 ℃. When selecting, if the measured temperature is around 200 ℃, thermistor measurement should be chosen. If the measured temperature is around 600 ℃, S-type or B-type thermocouple should be selected. If the measured temperature is between 1200 and 1600 ℃, S-type or B-type thermocouple should be chosen.

(1) Characteristics of Thermocouples

① High measurement accuracy. Because the thermocouple is in direct contact with the measured object and is not affected by the intermediate medium.

② Wide measurement range. Commonly used thermocouples can measure continuously from -50~+1600 ℃, while some special thermocouples can measure temperatures as low as -269 ℃ (such as gold iron nickel chromium) and as high as+2800 ℃ (such as tungsten rhenium).

③ Simple construction and easy to use. Thermocouples are usually composed of two different types of metal wires, and are not limited by size or opening. They have protective sleeves on the outside, making them very convenient to use.

2. Types and Structure Formation of Thermocouples

④ It also has the advantages of good linearity, large thermoelectric potential, high sensitivity, good stability and uniformity, strong antioxidant performance, and low price, and can be widely used in oxidizing inert atmospheres by users.

(2) Types of thermocouples

Commonly used thermocouples can be divided into two categories: standard thermocouples and non-standard thermocouples. The standard thermocouple referred to refers to a thermocouple that has a national standard that specifies the relationship between its thermoelectric potential and temperature, allows for errors, and has a unified standard scale. It has a matching display instrument available for selection. Non standardized thermocouples are not as widely used or of the same order of magnitude as standardized thermocouples, and generally do not have a unified calibration table. They are mainly used for measurements in certain special occasions.

(3) In order to ensure the reliable and stable operation of the thermocouple, the structural requirements for it are as follows:

① The welding of the two thermoelectric electrodes that make up the thermocouple must be firm;

② The two thermoelectric electrodes should be well insulated from each other to prevent short circuits;

③ The connection between the compensating wire and the free end of the thermocouple should be convenient and reliable;

④ The protective sleeve should ensure sufficient isolation between the thermoelectric electrode and harmful media.