Thermocouples and RTDs are all contact-type temperature measurements in temperature measurement. Although the same effect is used to measure the temperature of objects, their principles and characteristics are not the same.
First, introduce the thermocouple, thermocouple is a wide range of temperature devices used in temperature measurement, his main feature is a wide temperature range, performance is relatively stable, while the structure is simple, dynamic response is good, more able to remotely 4-20mA electrical signal For easy automatic control and centralized control. Thermocouple temperature measurement principle is based on the thermoelectric effect. Connecting two different conductors or semiconductors into a closed loop, when the temperature at two junctions is different, a thermoelectric potential will be generated in the loop. This phenomenon is called the thermoelectric effect, also known as the Seebeck effect. The thermoelectric potential generated in a closed loop has two potential components: a thermoelectric potential and a contact potential. Thermoelectric potential refers to the potential generated by the two ends of the same conductor due to different temperatures. Different conductors have different electron densities, so the potentials they generate are also different. The contact potential, as the name implies, means that two different conductors are in contact. Because their electron density is different, they produce a certain amount of electron diffusion. When they reach a certain equilibrium, the potential formed depends on the material properties of the two different conductors and the temperature of their contact points. At present, thermocouples used in the world have a standard specification. Internationally, thermocouples are divided into eight different divisions, namely B, R, S, K, N, E, J, and T. The measurement temperature can be low. Measuring 270 degrees below zero, up to 1800 degrees Celsius, in which B, R, and S belong to platinum series thermocouples. Since platinum belongs to precious metals, they are also known as precious metal thermocouples and the rest are called cheap metal thermoelectrics. I. There are two types of thermocouples, common type and armor type. General thermocouples are generally composed of hot electrodes, insulating tubes, protective tubes, and junction boxes. Armored thermocouples are assembled by combining thermocouple wires, insulating materials, and metal protective tubes. Extensive processing of a solid combination. But the electric signal of the thermocouple needs a kind of special wire to transmit, this kind of wire is called compensating wire. Different thermocouples require different compensating conductors, whose main function is to connect with the thermocouple, and keep the reference end of the thermocouple away from the power source, so that the reference junction temperature is stable. Compensation wire is divided into compensation type and extension type. The chemical composition of the extension wire is the same as that of the compensated thermocouple. However, in practice, the extension wire is not the same material as the thermocouple. Generally, the heat wire is used. Even the wires with the same electron density are replaced. The wire of the compensation wire and the thermocouple is generally very clear. The positive pole of the thermocouple connects the red wire of the compensation wire, and the negative pole connects the remaining colors. Most of the material of the general compensation wire is copper-nickel alloy.
Secondly, we introduce the thermal resistance. Although the thermal resistance is widely used in the industry, due to his temperature range, his application has been limited. The temperature measurement principle of the thermal resistance is based on the resistance value of the conductor or semiconductor. Changes in temperature characteristics. Its advantages are also many, it can also transmit remote signals, high sensitivity, strong stability, interchangeability and accuracy are better, but the need for power excitation, can not be instantaneous measurement of temperature changes. Industrial thermal resistors generally use Pt100, Pt10, Cu50, Cu100, platinum thermal resistance temperature measurement range is generally below 200-800 degrees Celsius, copper thermal resistance is minus 40 to 140 degrees Celsius. Thermal resistance is the same type of discrimination as thermocouples, but he does not need compensating wires and is cheaper than hot spots.
First, introduce the thermocouple, thermocouple is a wide range of temperature devices used in temperature measurement, his main feature is a wide temperature range, performance is relatively stable, while the structure is simple, dynamic response is good, more able to remotely 4-20mA electrical signal For easy automatic control and centralized control. Thermocouple temperature measurement principle is based on the thermoelectric effect. Connecting two different conductors or semiconductors into a closed loop, when the temperature at two junctions is different, a thermoelectric potential will be generated in the loop. This phenomenon is called the thermoelectric effect, also known as the Seebeck effect. The thermoelectric potential generated in a closed loop has two potential components: a thermoelectric potential and a contact potential. Thermoelectric potential refers to the potential generated by the two ends of the same conductor due to different temperatures. Different conductors have different electron densities, so the potentials they generate are also different. The contact potential, as the name implies, means that two different conductors are in contact. Because their electron density is different, they produce a certain amount of electron diffusion. When they reach a certain equilibrium, the potential formed depends on the material properties of the two different conductors and the temperature of their contact points. At present, thermocouples used in the world have a standard specification. Internationally, thermocouples are divided into eight different divisions, namely B, R, S, K, N, E, J, and T. The measurement temperature can be low. Measuring 270 degrees below zero, up to 1800 degrees Celsius, in which B, R, and S belong to platinum series thermocouples. Since platinum belongs to precious metals, they are also known as precious metal thermocouples and the rest are called cheap metal thermoelectrics. I. There are two types of thermocouples, common type and armor type. General thermocouples are generally composed of hot electrodes, insulating tubes, protective tubes, and junction boxes. Armored thermocouples are assembled by combining thermocouple wires, insulating materials, and metal protective tubes. Extensive processing of a solid combination. But the electric signal of the thermocouple needs a kind of special wire to transmit, this kind of wire is called compensating wire. Different thermocouples require different compensating conductors, whose main function is to connect with the thermocouple, and keep the reference end of the thermocouple away from the power source, so that the reference junction temperature is stable. Compensation wire is divided into compensation type and extension type. The chemical composition of the extension wire is the same as that of the compensated thermocouple. However, in practice, the extension wire is not the same material as the thermocouple. Generally, the heat wire is used. Even the wires with the same electron density are replaced. The wire of the compensation wire and the thermocouple is generally very clear. The positive pole of the thermocouple connects the red wire of the compensation wire, and the negative pole connects the remaining colors. Most of the material of the general compensation wire is copper-nickel alloy.
Secondly, we introduce the thermal resistance. Although the thermal resistance is widely used in the industry, due to his temperature range, his application has been limited. The temperature measurement principle of the thermal resistance is based on the resistance value of the conductor or semiconductor. Changes in temperature characteristics. Its advantages are also many, it can also transmit remote signals, high sensitivity, strong stability, interchangeability and accuracy are better, but the need for power excitation, can not be instantaneous measurement of temperature changes. Industrial thermal resistors generally use Pt100, Pt10, Cu50, Cu100, platinum thermal resistance temperature measurement range is generally below 200-800 degrees Celsius, copper thermal resistance is minus 40 to 140 degrees Celsius. Thermal resistance is the same type of discrimination as thermocouples, but he does not need compensating wires and is cheaper than hot spots.
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