和铠装电偶是工矿企业和科研院所常用的温度测量仪表。 Armored thermal resistance and armored thermocouple are temperature measurement instruments commonly used by industrial and mining enterprises and scientific research institutes. The correct installation of thermocouples and thermal resistors is an important factor in ensuring their measurement accuracy. The following are some introductions based on the usual installation methods, and I hope to provide some reference for everyone's actual work.
和铠装电偶的安装应尽可能保持垂直，以防止保护套管在高温下产生变形，但在有流速的情况下，则必须迎着被测介质的流向插入，以保证测温元件与流体的充分接触以保证其测量精度。 First, the installation of the armored thermal resistance and the armored couple should be kept as vertical as possible to prevent the protective sleeve from deforming at high temperatures. However, under the condition of flow velocity, it must be inserted in the direction of the measured medium to ensure The temperature measurement element is in full contact with the fluid to ensure its measurement accuracy. In addition, thermocouples and thermal resistors should be installed in pipelines with a protective layer as much as possible to prevent heat loss. Secondly, when thermocouples and thermal resistors are installed in negative pressure pipelines, the tightness of the measurement place must be ensured to prevent cold air from entering and make the reading low. When the thermocouple and RTD are installed outdoors, the cover of the junction box of the thermocouple and RTD should be up and the inlet should be down to prevent rain or dust from entering the junction box and damaging the thermocouple and RTD junction box. Wiring affects its measurement accuracy. The wiring of thermocouples and resistance thermometers should be checked frequently. Especially, because of the high hardness of the material of the compensating wire, the thermocouple thermometer is very easy to disconnect from the terminal and cause disconnection failure. And check it frequently to obtain the correct measured temperature. 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 not the same. First introduce the armored thermocouple, which is the temperature The most widely used temperature device in the measurement, his main features are a wide range of kissing, stable performance, simple structure, good dynamic response, and can transmit 4-20mA electrical signals remotely, which is convenient 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. The 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.The contact potential, as its name implies, is when two different conductors are in contact. Because of their different electron densities, there is a certain amount of electron diffusion. When they reach a certain equilibrium, the potential formed, the size of the contact potential depends on the material properties of the two different conductors and the temperature of their contact points. 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, and S belong to the platinum series thermocouples. Because platinum is a precious metal, they are also called noble metal thermocouples and the remaining few are called cheap metal thermoelectric I. There are two types of thermocouple structure, ordinary type and armored type. 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. Their main function is to connect with the thermocouple to keep the reference end of the thermocouple away from the power supply, so that the temperature of the reference end 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. Replace the wires with the same electron density. 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.
,热电阻虽然在工业中应用也比较广泛,但是由于他的测温范围使他的应用受到了一定的限制,热电阻的测温原理是基于导体或半导体的电阻值随着温度的变化而变化的特性。 Secondly, we introduce armored thermal resistance.Although thermal resistance is 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 of conductors or semiconductors. The characteristic that the value changes with temperature. 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 platinum thermal resistance is generally minus 200-800 degrees Celsius, and the 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.