Thermocouple wire

Thermocouple advantages

Thermocouple physical properties are determined by the percentage of components. Alumel - is very plastic and is able to maintain its strength for a long time. Constantan in an alloy with Iron, Copper and Chromel has a high electrical resistance that not dependent on temperature. Copel in the alloy with copper, iron and chromel have similar properties with constantan and a large thermelectromotive force, it has zero temperature coefficient of electric resistance, heat-resistant up to 600°C and resistant to corrosion. Chromel has a high heat-resistant and characterized by a high capacity to change thermelectromotive forces.

The most important advantages of these alloys:

• heat resistance;
• low density;
• high specific electric resistance;
• small temperature coefficient of electric resistance;
• average temperature coefficient of linear expansion;
• significant thermelectromotive force.

What is thermocouple wire? It’s a metal combination made of alloys characterized by heat and electrical conductivity. The role of thermocouples: to measure and control over a wide temperature range. The wires are used as thermopiles, which are connected in series of parallel. Physical properties of thermocouple wire: temperature range, conductivity, magnetism.

Of course platinum thermocouple wire serves as a temperature sensor (for high temperature measurement). It is also used for converting heat into electrical power.  So this wire (thermocouple) contains platinum types B, R, S. As a result, the wire product is expensive and has low sensitivity.

What is thermocouple extension wire? It is a product very similar to higher-grade thermocouple (made of the same metals).  Extension wire usage: to connect to a measuring instrument which may be in some distance away without using any additional junctions or joins between dissimilar materials which may result in unnecessary voltages.

Thermocouple wire is indispensable in manufacture of thermocouples and compensating cables in a variety of rectifying and measuring devices, as well as used in automation systems, operating at very high temperatures. Thermocouple is the thermoelectric temperature transmitter consists of two different conductors, one side of the conductors fused and placed in the environment for measurement of temperature (so-called “hot contacts”) another two free sides are placed into a thermostat – “cold contact”.

Thermocouple action principle – is thermoelectric effect. It is based on the measurement of difference of potentials arising proportional to the temperature difference between conductors of different materials. It is the direct appointment of thermocouple measurement of very high temperatures. For accurate measurements at relatively low temperatures used thermocouple with a high ThermoEMF, most often thermocouple, where positive thermo electrode is Iron, Copper and Cromel and the negative ones - Constantan, Alumel and Copel. Continuous resistance thermocouple with thermoelectric characteristics and use of Copel electrode is to maintain the ability of the alloy at a temperature under 500°C.

Compensatory wire – transfer thermelectromotive force of free ends of a thermocouple to the measuring device. For compensation wires used cheaper thermocouple wire with not so strictly controlled settings. For manufacture of compensation wires used: Cromel marks K and KM, Constantan, Copel, etc. Constantan and Copel used in electrical measuring devices for production of normal standards of resistance.

Production, common with the work at high temperatures is essential thermocouple wire the price of which depends on the composition of its constituent components.

Varieties

Several types of thermocouples used for measurement of various sizes temperature:

• alumel-chromel, the range of measured temperature from -200 up to 1000°C;
• copel-chromel, a range of measured temperature from -200 up to 800°C;
• constantan-chromel, a range of measured temperature from -40 up to 900°C;
• iron-constantan - is used to measure the very low temperatures - to -190°C;
• copper-constantan - a range of measured temperatures between 250 to 300°C;
• iron - copel, a range of measured temperature from 0 to 760°C;
• tungsten-rhenium used for the measurement of high temperature in inert environment up to 3000°C