Thermal resistance is the most commonly used temperature detector in the medium and low temperature areas.
Thermal resistance is based on the characteristic that the resistance value of a conductor or semiconductor changes with temperature to measure temperature and temperature-related parameters. Thermal resistors are mostly made of pure metal materials. Currently, platinum and copper are the most widely used. Materials such as nickel, manganese and rhodium have been used to make thermal resistance. Thermal resistance usually needs to transmit the resistance signal to the computer control device or other secondary instruments through the lead.
Sino-Inst offers a variety of Thermal Resistance for temperature measurement. If you have any questions, please contact our sales engineers.
Sheathed thermal resistance
Sheathed thermal resistance uses the feature that when the
temperature of the material changes, its resistance will change too. When the resistance changes, the instrument will display relevant temperature corresponding to the resistance.
It is usually used along with display instruments, recording
instruments, electronic computers and so on. It is able to directly measure the temperature of liquid, steam and gas and solid surface within the range of -200℃～500℃.
Assembling thermal resistance
The assembled PT100 thermal resistance is assembled by thermal resistance/platinum resistance element, metal protection tube, magnesium oxide insulating powder, and extension wire.
The product has a simple structure and a wide range of applications. This method is used in most thermal resistance temperature measurement occasions. According to the requirements of different customers, it is made of wear-resistant, anti-corrosion, explosion-proof, waterproof and high-temperature resistant types.
- With temperature-sensing element of pressure spring type, so it has good anti-vibration performance;
- With no compensation wire, which is cost-saving
- High measurement accuracy;
- High mechanical strength, good pressure resistance;
- Imported thin-film resistor with reliable and stable performance;
Explosion-proof thermal resistance
Explosion-proof thermal resistance is based on the principle of explosion-proof material gap. Design the junction box and other components with sufficient strength. All parts that generate sparks, arcs and dangerous temperatures are sealed in the junction box cavity. When an explosion occurs in the cavity, The flame can be extinguished and cooled through the gap of the joint surface, so that the flame and temperature after the explosion can not be transmitted to the outside of the cavity. Therefore, explosion-proof.
Range of temperature measurement and the error tolerance
Pt100 is a platinum thermal resistance, its resistance is proportional to the change of temperature. It is often used for temperature detection in low temperature areas. It realizes the functions of industrial field temperature control signals of one input and two output, and one input and four output.
Pt100 platinum thermal resistance is currently widely used in high-precision temperature equipment such as medical, electrical, industrial, temperature calculation, resistance calculation, etc.
The main types of thermal resistance:
①Ordinary thermal resistance
From the temperature measurement principle of the thermal resistance, the change of the measured temperature is directly measured by the change of the resistance of the thermal resistance. Therefore, the change of the resistance of various wires such as the lead wire of the thermal resistance will affect the temperature measurement.
②End surface thermal resistance
The end-face thermal resistance temperature-sensing element is wound by a specially treated resistance wire, which is closely attached to the end face of the thermometer. Compared with general axial thermal resistance, it can reflect the actual temperature of the measured end surface more accurately and quickly. It is suitable for measuring the end surface temperature of bearing bushes and other mechanical parts.
③Armored thermal resistance
The armored thermal resistance is a solid body composed of temperature sensing elements (resistors), lead wires, insulating materials, and stainless steel sleeves. Its outer diameter is generally φ2–φ8mm, and the smallest can reach φmm.
Compared with ordinary thermal resistance, it has the following advantages:
- Small size, no internal air gap, thermal inertia, small measurement lag;
- Good mechanical properties, vibration resistance and impact resistance;
- It can be bent and is easy to install;
- Long service life.
④Explosion-proof thermal resistance
Explosion-proof thermal resistance through the junction box of special structure, the explosion of explosive mixed gas inside the shell due to the influence of sparks or arcs is confined in the junction box, and the production site will not cause excessive explosion. Explosion-proof thermal resistance can be used for temperature measurement in places with explosion hazard in Bla-B3c level zone.
The difference between thermal resistance and thermocouple
Difference 1: The principle of temperature measurement is different
Thermal resistance temperature measurement is based on the characteristic that the resistance value of a metal conductor increases with temperature. Its main features are high measurement accuracy and stable performance. Among them, the measurement accuracy of platinum thermal resistance is the highest. It is not only widely used in industrial temperature measurement, but also made into a standard reference instrument.
The thermocouple welds two conductors or semiconductors A and B of different materials to form a closed loop. When there is a temperature difference between the two attachment points 1 and 2 of the conductors A and B, an electromotive force is generated between the two. Thus, a large current is formed in the loop. This phenomenon is called the thermoelectric effect.
Difference 2: The classification of thermocouple and thermal resistance is different.
The common thermal resistance materials are mostly single metal. The most widely used thermal resistance materials are platinum and copper. Platinum resistance has high precision, good stability, and certain nonlinearity. The higher the temperature, the smaller the resistance change rate. Copper resistance There is a linear relationship between the resistance value and the temperature in the temperature measurement range, the number of temperature lines is large, and it is easy to be oxidized if it exceeds 150. The index numbers of the thermal resistance are Cu50, Pt100, Pt1000, etc. The letter in the front refers to the material of the thermal resistance, and the number behind is the resistance value of the thermal resistance.
A thermocouple is composed of two different conductors (called thermocouple wires or thermoelectrodes) connected at both ends into a loop. The common K-type thermocouple is composed of nickel-chromium-nickel silicon. Standardized thermocouples China Since January 1, 1988, thermocouples and thermal resistances have all been produced in accordance with IEC international standards. Seven standardized thermocouples of S, B, E, K, R, J, and T are designated as China’s unified design. Thermocouple.
Difference 3: Different temperature range
Thermal resistance is a commonly used temperature sensor in the middle and low temperature areas. It is divided into platinum thermal resistance, copper thermal resistance, etc. The temperature measurement range is also different. In general, thermal resistance can measure the temperature from -200 to 600 ℃.
Compared with the thermal resistance, the temperature measurement range of the thermocouple is much larger. The B-type thermocouple with the largest temperature measurement range can even measure the temperature of 0-1800 ℃. The ordinary K-type thermocouple can also measure Temperature of -40-1200℃. But because the measurement of thermocouple in low temperature area is not very accurate. Therefore, it is more appropriate to use thermal resistance when measuring lower temperature.
Difference 4: Different connection methods
There are currently three main ways to connect thermal resistance: two-wire, three-wire, and four-wire. The accuracy of the two-wire system is relatively low, while the four-wire system is more used for accurate measurement in the laboratory. Most of our commonly used thermal resistances are three-wire systems. This is because the circuit for measuring thermal resistance is generally an unbalanced bridge. A three-wire system is used. One wire is connected to the power terminal of the bridge. The other two are connected to the heat. The bridge arm where the resistance is located and the bridge arm adjacent to it. This can eliminate the measurement error caused by the wire line resistance, and greatly improve the accuracy.
Thermocouples are not so particular about thermal resistance. They are all two-wire systems. Unlike thermal resistance, the output resistance of thermocouple is mV signal.
Sino-Inst, Manufacuturer for Thermal Resistances, like: Armoured thermocouple, assembly thermocouple, explosion-proof thermocouple, etc.
Sino-Inst’s Thermal Resistances, made in China, Having good Quality, With better price. Our Temperature measurement instruments are widely used in China, India, Pakistan, US, and other countries.
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