Armored thermocouple

WRNK Armored thermocouple produced by shanghai automation instrumentation co., ltd. as a temperature measurement sensor, usually with the temperature transmitter, regulator and display instruments supporting the use of such a process control system for direct measurement or control of various production processes in the range of 0-1800 ℃ fluid, Steam and gas medium and solid surface temperature. The armor thermocouple has many advantages such as bending, high pressure resistance, fast thermal response time and ruggedness. It is the same as the industrial assembly thermocouple, which is usually used as a sensor for measuring temperature, usually with a display instrument, a recording instrument and an electronic regulator use.

brief introduction

The armored thermocouple has many advantages, such as bending, high pressure resistance, fast thermal response time and ruggedness. It is the same as the industrial assembly thermocouple, which is usually used as a sensor for measuring temperature, usually with a display instrument, a recording instrument and an electronic regulator Use, at the same time, can also be used as assembly thermocouple temperature sensor. It can directly measure the temperature of the liquid, vapor and its gaseous medium and solid surface from 0to 800C ℃in various production processes. Compared with the assembled thermocouple, armored thermocouple with flexible, high pressure, short thermal response time and rugged and so on.

working principle

Is two different components of the conductor at both ends of the welding, the formation of the loop, the temperature directly called the end of the work, the terminal end called cold end, also known as the reference side. When the working side and the reference side of the existence of temperature difference, it will generate heat in the loop, connected to the display instrument, the instrument will indicate the thermocouple generated by the corresponding thermoelectromotive force value. The thermoelectromotive force of the armored thermocouple will increase with the temperature of the measuring end. The size of the thermoelectromotive force is only related to the thermocouple conductor material and the temperature difference between the two ends, regardless of the length and diameter of the hot electrode. Armored thermocouple structure principle is that by the conductor, high insulation magnesia, jacket 1Cr18Ni9Ti stainless steel protection tube, after repeated drawn from one. Armored thermocouple products mainly by the junction box, terminal blocks and armored thermocouple composed of the basic structure, and with a variety of installation of fixed devices.

Features

Armored thermocouple is the most widely used temperature measurement device, its main feature is the wide temperature range, the performance is relatively stable, while the structure is simple, dynamic response is good, more remote transmission 4-20mA electrical signal, easy to control And centralized control. Thermocouple temperature measurement principle is based on thermoelectric effect. Connect two different conductors or semiconductors to a closed loop. When the temperatures at the two junctions are different, the thermoelectric potential will be generated in the loop. This phenomenon is called thermoelectric effect, also known as the Seebeck effect. The thermoelectric potential generated in the closed loop has two potentials; the temperature difference potential and the contact potential. Temperature difference potential refers to the same conductor at both ends due to different temperatures generated by the potential, different conductors have different electron density, so they produce the potential is not the same, and the contact potential as the name suggests refers to two different contact with the conductor, Because of their electronic density, there is a certain amount of electron diffusion, and when they reach a certain equilibrium, the magnitude of the contact potential depends on the material properties of the two different conductors and the temperature of their contact points.

Internationally used thermocouples have a standard specification, the international requirements of the thermocouple is divided into eight different degrees, respectively, B, R, S, K, N, E, J and T, the minimum measured temperature measurement Minus 270 degrees Celsius, up to 1800 degrees Celsius, where B, R, S are platinum series thermocouple, because platinum is precious metals, so they are called precious metal thermocouple and the rest are called cheap metal thermocouple The Thermocouple structure has two kinds, ordinary type and armored type. Ordinary thermocouple is generally composed of hot electrodes, insulated tubes, protective sleeves and junction boxes and other parts, and armored thermocouple is the thermocouple wire, insulation materials and metal protective sleeve combination of the three after assembly A solid combination of workmanship. But the thermocouple's electric signal requires a special wire to carry, this wire we call the compensation wire. Different thermocouples require different compensation wires, the main role is to connect with the thermocouple, so that the thermocouple reference side away from the power supply, so that the reference end temperature stability. Compensation wire is divided into two types of compensation and extension, extending the chemical composition of the wire and the compensated thermocouple the same, but in practice, the extension of the wire is not the same material and thermocouple metal, the general use and thermal Even with the same electronic density of the wire instead. The connection of the compensating conductor to the thermocouple is generally clear, and the positive pole of the thermocouple connects the red wire of the compensating conductor, while the negative pole connects the remaining color. Most of the material of the compensation wire is copper nickel alloy.

Temperature compensation

As the armored thermocouple materials are generally more expensive (especially when the use of precious metals), and the temperature measurement point to the instrument are far away, in order to save armored thermocouple material, reduce costs, usually using compensation wire to armored thermoelectric Even the cold end (free end) extends to a relatively stable temperature control room, connected to the instrument terminal. It must be pointed out that the role of the thermocouple compensation wire only extends the thermal electrode so that the cold end of the armored thermocouple is moved to the instrument terminal of the control room itself which does not eliminate the effect of the cold junction temperature change on the temperature measurement effect. Therefore, other correction methods need to be used to compensate the cold junction temperature t0 ≠ 0 ℃ on the temperature of the impact. In the use of armored thermocouple compensation wire must pay attention to the model match, polarity can not be wrong, compensation wire and armored thermocouple connection side of the temperature can not exceed 100 ℃.

Principle of temperature measurement

The electric couple is welded together with two different components of the conductor, the two ends of the temperature is different, there will be thermoelectric potential in the loop, so the potential even

Is a temperature sensor that measures the potential to measure the temperature, which is a converter that converts the temperature signal into an electrical signal and is displayed by the display instrument.

Thermocouple measurement of the basic principle of temperature is the thermoelectric effect, the two different components of the metal conductor connected to the end of a closed loop, such as the two junctions temperature, then the circuit will produce thermal electromotive force, the formation of thermal current, which is Thermoelectric effect. The thermocouple is one of two different metal materials welded together, one end of the welding called the measurement side, the end of the welding is not called the reference side, the reference end in use is usually constant at a certain temperature (such as 00C) when the measurement side of the heating , There is a thermoelectric potential at the junction. If the reference terminal temperature is constant, the size and direction of the thermoelectric power are only related to the characteristics of the two metal materials and the temperature of the measuring end, regardless of the fine length and length of the potential couple. When the temperature at the measuring end changes, the potential potential also changes, and there is a fixed function relationship between the temperature and the thermoelectric potential, and the temperature can be measured using this relationship.

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