Armoured N Type Thermocouple Temperature Sensor Accurate Measurement

Armoured N Type Thermocouple Temperature Sensor Accurate Measurement

Armoured Temperature Sensor Industrial Design Accurate Measurement

1. explain

Armoured thermocouple is the most widely used temperature device in temperature measurement. Mainly characterized by wide range of temperature measurement, relatively stable performance, simple structure, and good dynamic response, armoured thermocouple can transmit 4-20mA electrical signals remotely, convenient for automatic control and centralized control. The thermocouple works based on the thermoelectric effect. Two different conductors or semiconductors are connected into a closed loop and when the temperature at the two junctions is different, thermoelectric potential will be generated in the loop, a phenomenon called pyroelectric effect, also known as Seebeck effect. The thermoelectric potential generated in the closed loop is composed of two kinds of electric potential: thermoelectric potential and 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 they generate different potentials. The contact potential, as the name implies, refers to the circumstance when two different conductors are in contact, a certain amount of electron diffusion occurs because their electron densities are different. When they reach certain equilibrium, the potential formed by the contact potential depends on the material properties of the two different conductors and the temperature of their contact points.

Armored thermocouples have the advantages of flexibility, high pressure resistance, fast thermal response time, sturdiness and durability. Like the assembled thermocouples, armored thermocouples, as temperature sensors, are generally used together with display instruments, recorders and electronic regulator. In addition, armored thermocouple can also be used as the temperature sensing element of the assembled thermocouple, directly measure the temperature of liquid, steam and gaseous media and solid surfaces in the range of 0℃～1,100℃ in various production processes. The introduction of parameters and characteristics of the armored thermocouple allows everyone to have a deeper understanding. Thermocouples are not universal and should be selected according to actual conditions and requirements. Choosing the most suitable product can bring beneficial effects to production. Otherwise, it will only increase troubles and cause unnecessary quality issues.

Generally armoured thermocouples can be used to measure the surface or internal temperature of gas, liquid, steam and solid in the range of 0～1300℃, and can be used together with digital instruments, recording and regulating instruments, PLC, data collectors or computers. As a new generation of temperature sensors, it can be widely used in various sectors such as metallurgy, petroleum, chemical industry, electric power, light industry, textile, food, national defense and scientific research.

There is an international standard specification for thermocouples. The international regulations stipulate that thermocouples are divided into eight different divisions, namely B, R, S, K, N, E, J and T. The measurement temperature can be as low as minus 270 degrees Celsius and as high as 1,800 degrees Celsius. In addition, B, R and S belong to the platinum series thermocouples and, since platinum is a precious metal, such platinum series thermocouples are also called precious metal thermocouples and the remaining ones the cheap metals thermocouples.

There are two types of thermocouples: common thermocouples and armored thermocouples. Common thermocouples are generally composed of thermode, insulating tube, protective sleeve and junction box, while armored thermocouple is a solid combination formed by stretching after assembling the thermocouple wire, insulating material and metal protective sleeve. The electrical signal of thermocouple, however, needs a special transmission wire called compensation wire. Different thermocouples require different compensation wires, and their main function is to connect with the thermocouple to keep the reference terminal away from the power supply, thus maintaining a stable temperature at the reference terminal. Compensation wires are divided into two types: compensation type and extension type. The latter has the same chemical composition as that of the thermocouple being compensated. However, in practice, the extension wire is not made of the same material as the thermocouple, generally replaced by wires with the same electron density as the thermocouple. The connection between the compensation wire and the thermocouple is generally very clear, that is, the positive pole of the thermocouple is connected to the red wire of the compensation wire and the negative pole to the remaining colors. Most of the common compensation wires are made of copper-nickel alloy.

2. Product structure

Armored thermocouple and armored thermal resistor are formed by repeatedly drawing the thermode (wire) magnesium oxide insulator and 1Cr18Ni9Ti stainless steel tube.

1 Material structure of armored thermocouple

2 Structure of the measuring terminal

The measuring end of armored thermocouple is divided into two types: insulated type and shell connected type

3. Form of installation and fixation

User can use the fixing device for installation. Except for the product without fixing devices, armored galvanic couples and resistors generally involve four structure types: fixed ferrule, movable ferrule, fixed flange and movable flange. The products of fixed ferrule type are for one-time fixation by users, and the movable ferrule type can be used for fixation for multiple times.

4. Installation of free end (junction box)

The junction box is used to connect the free end of the thermocouple and the display instrument. At present, many structural forms are available: the simple type, the waterproof type, the handle type, the plug-in type, and the compensation wire type (extended wire type), etc.