![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
What is the measurement principle of a thermocouple?
The working principle of the thermocouple is based on the seeback effect, that is, the two different components of the conductor are connected into a loop at both ends. If the temperatures of the two connecting ends are different, the thermal phenomenon occurs in the circuit.
Thermocouples consist of two different wires (hot electrodes), one end of which is soldered to each other, forming the measuring end (also called the working end) of the thermocouple. It is inserted into the medium at the temperature to be measured; the other end of the thermocouple (reference or free end) is connected to the display instrument. If there is a temperature difference between the measuring and reference terminals of the thermocouple, the display meter will indicate the thermo-electromotive force generated by the thermocouple.
Second, the measurement principle of thermal resistance?
Thermal resistance is the use of metal conductors or semi-conductors that measure the temperature as their resistance changes with temperature. The heated part of the thermal resistor (thermoelement) is a skeleton that is made of a thin metal wire that is evenly wound around an insulating material. It is formed on the substrate by or on a laser sputtering process. When the measured medium has a temperature gradient, the measured temperature is the average temperature of the dielectric layer within the temperature sensing element range.
Third, how to choose thermocouple and thermal resistance?
According to the range of temperature measurement, the thermocouple is generally selected above 500°C, and the thermal resistance is generally selected below 500°C;
According to the measurement accuracy selection: the higher the accuracy of the choice of thermal resistance, the accuracy of the required choice of thermocouple;
Select according to the measuring range: Generally, the "point" temperature measured by the thermocouple, and the average spatial temperature measured by the thermal resistance;
Fourth, what is the advantage of armored thermocouples?
In the standard of IEC1515, the name is “mineralinsulatedthermocouplecableâ€, which is an inorganic mineral insulated thermocouple cable. The hot electrode, insulating material and sheath are formed by integral drawing, and the outer surface seems to be covered with a layer of "armored", so it is called armored thermocouple. Compared with the general assembly type thermocouple, it has the advantages of high pressure resistance, good bending performance, good oxidation resistance and long service life.
5. What are the index numbers of thermocouples? What are the characteristics?
Thermocouple index number is mainly S, R, B, N, K, E, J, T and other types. Among them, S, R, and B belong to noble metal thermocouples, and N, K, E, J, and T belong to inexpensive metal thermocouples.
The S index No. is characterized by strong anti-oxidation performance, and it should be used continuously in oxidizing and inert atmospheres. The long-term use temperature is 1400°C and short-term 1600°C. In all thermocouples, the S-index number has the highest level of accuracy and is commonly used as a standard thermocouple;
The R division number is about 15% larger than the S division number in addition to the thermal electromotive force, and the other properties are almost the same; the B division number has a very small thermo-electromotive force at room temperature, so the compensation conductor is generally not used in the measurement. Its long-term use temperature is 1600 °C, short-term 1800 °C. It can be used in oxidizing or neutral atmosphere, but it can also be used under vacuum conditions for a short time.
The N index number is characterized by high temperature oxidation resistance at 1300°C, long-term stability of the thermo-electromotive force and good reproducibility of the short-term thermal cycle, good resistance to nuclear irradiation and low temperature resistance, and can partially replace the S index number Thermocouple
The K indexing number is characterized by its strong anti-oxidation properties, and it should be used continuously in oxidizing and inert atmospheres. The long-term use temperature is 1000°C and the short-term 1200°C. Most widely used among all thermocouples;
The feature of the E index number is that among the commonly used thermocouples, the thermo-electromotive force is the highest, that is, the sensitivity is the highest. Should be used continuously in oxidizing, inert atmosphere, using temperature 0-800°C;
The J indexing number is characterized by its ability to be used in both oxidizing atmosphere (up to 750°C) and reducing atmosphere (upper temperature up to 950°C), and resistant to H2 and CO gas corrosion. It is mostly used in oil refining and chemical industry.
The T-index number is characterized by the highest level of accuracy among all inexpensive metal thermocouples and is commonly used to measure temperatures below 300°C.
Sixth, there are several ways to draw the thermal resistance? What are the effects?
There are three types of lead wire for thermal resistance: two-wire, three-wire, and four-wire.
The 2-wire thermal resistance wiring is simple, but the additional error of the lead resistance is required. Therefore, it is not suitable to manufacture thermal resistors of Class A accuracy, and the lead wires and wires should not be too long during use.
The 3-wire system eliminates the influence of the lead resistance and the measurement accuracy is higher than the 2-wire system. As a process detection element, it is the most widely used.
The 4-wire system not only eliminates the influence of the lead resistance, but also eliminates the influence of the resistance when the resistance of the connecting wires is the same. In the high-precision measurement, the 4-wire system is used.
7. What are the advantages and disadvantages of an N-type thermocouple compared to a K-type thermocouple?
N-type thermocouple advantages:
High temperature anti-oxidation ability, strong long-term stability. The preferential oxidation of Cr and Si elements in the nickel-chromium cathode of K-type thermocouple causes alloy composition non-uniformity and thermo-electromotive force drift, etc. The addition of Cr and Si to the N-type thermocouple increases the oxidation mode of the nickel-chromium alloy from internal to external oxidation. Oxidation, resulting in the oxidation reaction only on the surface;
Low temperature short-term thermal cycle stability is good, and suppresses the magnetic transition;
Strong nuclear radiation resistance. The N-type thermocouple cancels the Mn and Co elements in the K-type eutectic element, which further enhances the ability to resist neutron irradiation.
In the range of 400-1300°C, the thermoelectric characteristics of the N-type thermocouple are better than that of the K-type.
Disadvantages of N-type thermocouples:
The material of N type thermocouple is harder than K type and it is difficult to process;
The price is relatively expensive. The coefficient of thermal expansion of the N-type thermocouple is 15% lower than that of stainless steel. Therefore, the outer casing of the N-type armored thermocouple should be made of NiCrSi/NiSi alloy.
Larger nonlinearity error in the range of -200~400°C
The working principle of the thermocouple is based on the seeback effect, that is, the two different components of the conductor are connected into a loop at both ends. If the temperatures of the two connecting ends are different, the thermal phenomenon occurs in the circuit.
Thermocouples consist of two different wires (hot electrodes), one end of which is soldered to each other, forming the measuring end (also called the working end) of the thermocouple. It is inserted into the medium at the temperature to be measured; the other end of the thermocouple (reference or free end) is connected to the display instrument. If there is a temperature difference between the measuring and reference terminals of the thermocouple, the display meter will indicate the thermo-electromotive force generated by the thermocouple.
Second, the measurement principle of thermal resistance?
Thermal resistance is the use of metal conductors or semi-conductors that measure the temperature as their resistance changes with temperature. The heated part of the thermal resistor (thermoelement) is a skeleton that is made of a thin metal wire that is evenly wound around an insulating material. It is formed on the substrate by or on a laser sputtering process. When the measured medium has a temperature gradient, the measured temperature is the average temperature of the dielectric layer within the temperature sensing element range.
Third, how to choose thermocouple and thermal resistance?
According to the range of temperature measurement, the thermocouple is generally selected above 500°C, and the thermal resistance is generally selected below 500°C;
According to the measurement accuracy selection: the higher the accuracy of the choice of thermal resistance, the accuracy of the required choice of thermocouple;
Select according to the measuring range: Generally, the "point" temperature measured by the thermocouple, and the average spatial temperature measured by the thermal resistance;
Fourth, what is the advantage of armored thermocouples?
In the standard of IEC1515, the name is “mineralinsulatedthermocouplecableâ€, which is an inorganic mineral insulated thermocouple cable. The hot electrode, insulating material and sheath are formed by integral drawing, and the outer surface seems to be covered with a layer of "armored", so it is called armored thermocouple. Compared with the general assembly type thermocouple, it has the advantages of high pressure resistance, good bending performance, good oxidation resistance and long service life.
5. What are the index numbers of thermocouples? What are the characteristics?
Thermocouple index number is mainly S, R, B, N, K, E, J, T and other types. Among them, S, R, and B belong to noble metal thermocouples, and N, K, E, J, and T belong to inexpensive metal thermocouples.
The S index No. is characterized by strong anti-oxidation performance, and it should be used continuously in oxidizing and inert atmospheres. The long-term use temperature is 1400°C and short-term 1600°C. In all thermocouples, the S-index number has the highest level of accuracy and is commonly used as a standard thermocouple;
The R division number is about 15% larger than the S division number in addition to the thermal electromotive force, and the other properties are almost the same; the B division number has a very small thermo-electromotive force at room temperature, so the compensation conductor is generally not used in the measurement. Its long-term use temperature is 1600 °C, short-term 1800 °C. It can be used in oxidizing or neutral atmosphere, but it can also be used under vacuum conditions for a short time.
The N index number is characterized by high temperature oxidation resistance at 1300°C, long-term stability of the thermo-electromotive force and good reproducibility of the short-term thermal cycle, good resistance to nuclear irradiation and low temperature resistance, and can partially replace the S index number Thermocouple
The K indexing number is characterized by its strong anti-oxidation properties, and it should be used continuously in oxidizing and inert atmospheres. The long-term use temperature is 1000°C and the short-term 1200°C. Most widely used among all thermocouples;
The feature of the E index number is that among the commonly used thermocouples, the thermo-electromotive force is the highest, that is, the sensitivity is the highest. Should be used continuously in oxidizing, inert atmosphere, using temperature 0-800°C;
The J indexing number is characterized by its ability to be used in both oxidizing atmosphere (up to 750°C) and reducing atmosphere (upper temperature up to 950°C), and resistant to H2 and CO gas corrosion. It is mostly used in oil refining and chemical industry.
The T-index number is characterized by the highest level of accuracy among all inexpensive metal thermocouples and is commonly used to measure temperatures below 300°C.
Sixth, there are several ways to draw the thermal resistance? What are the effects?
There are three types of lead wire for thermal resistance: two-wire, three-wire, and four-wire.
The 2-wire thermal resistance wiring is simple, but the additional error of the lead resistance is required. Therefore, it is not suitable to manufacture thermal resistors of Class A accuracy, and the lead wires and wires should not be too long during use.
The 3-wire system eliminates the influence of the lead resistance and the measurement accuracy is higher than the 2-wire system. As a process detection element, it is the most widely used.
The 4-wire system not only eliminates the influence of the lead resistance, but also eliminates the influence of the resistance when the resistance of the connecting wires is the same. In the high-precision measurement, the 4-wire system is used.
7. What are the advantages and disadvantages of an N-type thermocouple compared to a K-type thermocouple?
N-type thermocouple advantages:
High temperature anti-oxidation ability, strong long-term stability. The preferential oxidation of Cr and Si elements in the nickel-chromium cathode of K-type thermocouple causes alloy composition non-uniformity and thermo-electromotive force drift, etc. The addition of Cr and Si to the N-type thermocouple increases the oxidation mode of the nickel-chromium alloy from internal to external oxidation. Oxidation, resulting in the oxidation reaction only on the surface;
Low temperature short-term thermal cycle stability is good, and suppresses the magnetic transition;
Strong nuclear radiation resistance. The N-type thermocouple cancels the Mn and Co elements in the K-type eutectic element, which further enhances the ability to resist neutron irradiation.
In the range of 400-1300°C, the thermoelectric characteristics of the N-type thermocouple are better than that of the K-type.
Disadvantages of N-type thermocouples:
The material of N type thermocouple is harder than K type and it is difficult to process;
The price is relatively expensive. The coefficient of thermal expansion of the N-type thermocouple is 15% lower than that of stainless steel. Therefore, the outer casing of the N-type armored thermocouple should be made of NiCrSi/NiSi alloy.
Larger nonlinearity error in the range of -200~400°C
Cement Jumbo Bag,Bags Of Cement Wickes,Menards Cement Bags,Sand Cement Bags
Guangdong Yingtong Paper Co., Ltd , https://www.yingtongpacking.com