均属于温度测量中的接触式测温,尽管其作用相同都是测量物体的温度,但是他们的原理与特点却不尽相同. Thermocouples and thermal resistors are both contact-type temperature measurement in temperature measurement.Although their functions are the same to measure the temperature of objects, their principles and characteristics are different.
First of all, we introduce thermal resistance.Although thermal resistance is also widely used in industry, its application is limited due to its temperature measurement range.The principle of temperature measurement of thermal resistance is based on the resistance value of conductors or semiconductors. As temperature changes
And changing characteristics. It also has many advantages. It can also transmit electrical signals remotely, with high sensitivity, strong stability, interchangeability and accuracy. However, it requires power supply excitation and cannot measure temperature changes instantaneously. Industrial thermal resistance generally uses Pt100, Pt10, Cu50, Cu100
The temperature range of PT1000 platinum thermal resistance is generally minus 200-800 degrees Celsius, and copper thermal resistance is minus 40 to 140 degrees Celsius. The thermal resistance is the same type as the thermocouple, but it does not need a compensation wire and is cheaper than a hot couple.
则是将热电偶丝,绝缘材料和金属保护套管三者组合装配后,经过拉伸加工而成的一种坚实的组合体。 Ordinary thermocouples are generally composed of thermal electrodes, insulating tubes, protective sleeves, and junction boxes.The armored thermocouples are assembled by combining the thermocouple wire, insulating material and metal protective sleeve. It is a solid combination made by drawing.
But the electric signal of the thermocouple needs a special kind of wire to transmit, this kind of wire we call compensation wire. Different thermocouples require different compensation wires.The main function is to connect the thermocouple to keep the reference end of the thermocouple away from the power supply, so that the reference end
The temperature is stable. The compensating wire is divided into two types: compensating and extending.The chemical composition of the extending wire is the same as that of the thermocouple being compensated.However, in practice, the extending wire is not made of the same material as the thermocouple. Even with the same electron density
Wire instead. The connection between the compensation wire and the thermocouple is generally very clear. The positive electrode of the thermocouple is connected to the red wire of the compensation wire, while the negative electrode is connected to the remaining color. Most of the materials of general compensation wires are copper-nickel alloys.
The second is to introduce the thermocouple.The thermocouple is the most widely used temperature device in temperature measurement.Its main features are a wide range of kissing, stable performance, simple structure, good dynamic response, and the conversion transmitter can be farther away. 4-20mA current signal for automatic
Control and centralized control. The principle of thermocouple temperature measurement is based on the thermoelectric effect. When two different conductors or semiconductors are connected to form a closed loop, when the temperature at the two junctions is different, a thermoelectric potential will be generated in the loop. This phenomenon is called the thermoelectric effect, and it is also called the Seebeck effect.
The thermoelectric potential generated in a closed loop is composed of two potentials; the temperature difference potential and the contact potential. Temperature difference 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 not the same, and the contact potentials
As the name implies, it means that when two different conductors are in contact, a certain amount of electron diffusion is generated because their electron densities are different. When they reach a certain equilibrium, the potential formed is the size of the contact potential, which depends on the material properties of the two different conductors. And their touch points
temperature. At present, the thermocouples used internationally have a standard specification.The internationally specified thermocouples are divided into eight different graduations, which are B, R, S, K, N, E, J, and T. The lowest possible measurement temperature is Measured at minus 270 degrees Celsius, up to 1800 degrees Celsius, of which B, R, S belong to platinum
Since the series of thermocouples are precious metals, they are also called noble metal thermocouples and the remaining ones are called cheap metal thermocouples . There are two types of thermocouple structure, ordinary type and armored type.