A high-sensitivity thin-film thermopile heat flow meter

Abstract

The present invention provides a highly sensitive thin-film thermopile heat flux meter, comprising a substrate; a lower thermal resistance layer disposed on the substrate; a thermopile thin film formed by overlapping multiple pairs of thermocouples end to end, disposed on the lower thermal resistance layer. Each pair of thermocouples comprises a positive thermocouple and a negative thermocouple connected in series, with the positive and negative thermocouples connected in a stepped manner. The lower thermal resistance layer covers below the hot junction where the positive and negative thermocouples are connected. An upper thermal resistance layer is disposed on the thermopile thin film and covers above the cold junction where the positive and negative thermocouples are connected. The two ends of the thermopile thin film are connected through positive and negative thermopile lead terminals, respectively. The negative and positive thermopile lead terminals are connected to form a thermocouple, and a temperature signal is measured through the lead terminals. The present invention can achieve transient measurement of temperature and heat flux density and has the advantages of fast response and high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal flow devices, and in particular to a high-sensitivity thin-film thermopile type thermal flow meter. Background Art

[0002] Today, numerous heat transfer problems remain unsolved in industrial and agricultural production, scientific research, aerospace, power engineering, and everyday life. With the rapid advancement of modern science and technology, temperature alone as the sole indicator of heat transfer is no longer sufficient. Consequently, the theory and technology of heat flow measurement are gaining increasing attention, and the research and application of heat flow sensors—heat flow probes and heat flow meters—has become more widespread. Due to the development of the aerospace industry and the practical needs of thermal energy engineering, there is an urgent need in aerospace, space technology, and other high-tech fields to develop sensors that can rapidly measure both temperature and heat flux. Therefore, to develop a combined temperature and heat flux sensor suitable for both engineering and aerospace applications, a transient temperature and heat flux combined sensor has emerged. This sensor utilizes the Seebeck measurement principle of thermocouples combined with thin-film technology to achieve transient temperature and heat flux measurements, thereby deriving transient temperature and heat flux values. Combined measurement of transient temperature and heat flux is a challenging issue in thermal engineering testing and remains a long-standing challenge. Research on the joint measurement of transient temperature and heat flow, especially the joint measurement of transient temperature and heat flow in small spaces, has positive significance for my country's energy conservation, aerospace and other fields.

[0003] After searching, we found:

[0004] The Chinese invention patent with authorization announcement number CN106017696B discloses a thermal resistance thin film thermopile type transient heat flux meter and its preparation method. "The heat flux meter includes a ceramic substrate and a positive thermocouple, a negative thermocouple, a thermocouple connection layer, an outer thermal resistance layer and an inner thermal resistance layer arranged on the ceramic substrate. The positive thermocouple and the negative thermocouple are connected through the thermocouple connection layer. The outer thermal resistance layer and the inner thermal resistance layer cover the positive thermocouple and the negative thermocouple. When the external environment applies a vertical heat flow on the heat flux meter, the thickness of the outer thermal resistance layer and the inner thermal resistance layer are different, and there is a temperature difference between the two adjacent hot nodes and the cold node. According to the Seebeck effect, there is a corresponding potential output, and its output potential is related to the heat flux density." The design is based on the thermal resistance thin film thermopile type transient heat flux meter, and uses the thermocouple temperature measurement principle to realize the transient measurement of heat flux density. This invention can realize the transient measurement of heat flux density, but cannot measure temperature at the same time. Summary of the Invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a high-sensitivity thin-film thermopile type heat flux meter that can realize the synchronous measurement of temperature and heat flux density, and has the characteristics of simple structure, fast response speed, large measurement temperature range, high measurement accuracy and high sensitivity.

[0006] The present invention is achieved through the following technical solutions:

[0007] According to one aspect of the present invention, there is provided a high-sensitivity thin-film thermopile type heat flow meter, comprising:

[0008] substrate;

[0009] a lower thermal resistance layer, disposed on the substrate;

[0010] A thermopile thin film formed by overlapping multiple pairs of thermocouples end to end is provided on the lower thermal resistance layer, wherein each pair of thermocouples is formed by a positive thermocouple and a negative thermocouple connected in series, and the positive thermocouple and the negative thermocouple are connected in a stepped manner; the lower thermal resistance layer covers below the hot node where the positive thermocouple and the negative thermocouple are connected;

[0011] an upper thermal resistance layer, provided on the thermopile film, wherein the upper thermal resistance layer covers the cold node where the positive thermocouple and the negative thermocouple are connected;

[0012] One end of the thermopile film is provided with a positive thermopile lead end for connection, and the other end of the thermopile film is provided with a negative thermopile lead end for connection; the thermopile film also has a temperature measurement function, the negative thermopile lead and the positive thermopile lead end are interconnected to form a thermocouple, and the temperature signal is measured through the leads.

[0013] Furthermore, the upper thermal resistance layer and the lower thermal resistance layer are made of the same material.

[0014] Furthermore, the thickness of the upper thermal resistance layer is 2-5 microns, and the thickness of the lower thermal resistance layer is 2-5 meters.

[0015] Furthermore, the thermopile film is composed of PtRh-Pt type thermocouple, Pt-ITO type thermocouple, WRe x -WRe y It is composed of any one of type thermocouple, ITO-In2O3 type thermocouple and K type thermocouple connected in series.

[0016] Furthermore, when the thermopile film is formed by a PtRh-Pt type thermocouple connected in series, the materials of the positive thermocouple and the positive thermopile lead end are both platinum-rhodium, and the materials of the negative thermocouple and the negative thermopile lead end are both platinum;

[0017] When the thermopile film is a Pt-ITO type thermocouple connected in series, the material of the positive thermocouple and the positive thermopile lead end are both Pt, and the material of the negative thermocouple and the negative thermopile lead end are both ITO;

[0018] When the thermopile film is WRe x -WRe y When the positive thermocouple is connected in series, the material of the positive thermocouple and the positive thermopile lead end are both WRe x The negative electrode thermocouple and the negative electrode thermopile lead end are made of WRe y ;

[0019] When the thermopile film is formed by connecting ITO-In2O3 type thermocouples in series, the materials of the positive thermocouple and the positive thermopile lead end are both ITO, and the materials of the negative thermocouple and the negative thermopile lead end are both In2O3;

[0020] When the thermopile film is formed by K-type thermocouples connected in series, the materials of the positive thermocouple and the positive thermopile lead end are both nickel-chromium, and the materials of the negative thermocouple and the negative thermopile lead end are both nickel-silicon.

[0021] Furthermore, the number of thermocouples in the thermopile film ranges from 20 to 160 pairs.

[0022] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0023] 1. The high-sensitivity thin-film thermopile heat flux meter of the present invention is composed of multiple pairs of thermocouples connected end to end to form a thin-film thermopile. The positive thermocouple lead end and the negative thermocouple lead end are connected through two lead ends, which can measure temperature. Through the influence of the thermal resistance layer, the positive thermopile lead end and the negative thermopile lead end can measure heat flux density, thereby realizing synchronous transient measurement of temperature and heat flux density.

[0024] 2. The high-sensitivity thin-film thermopile heat flux meter of the present invention adopts a unique structure in which a lower thermal resistance layer is arranged below the hot node and an upper thermal resistance layer is arranged above the cold node. Compared with the existing structure in which the thermal resistance layer is arranged above or below, or the design structure in which the hot and cold nodes are at the same physical height, the present invention can increase the temperature difference between the two ends, and the temperature difference can be larger, thereby improving the sensitivity of the heat flux meter sensor to heat flux density measurement and achieving a faster response.

[0025] 3. In addition to the conventional method of increasing the sensitivity by increasing the number of thermocouples in the thin-film thermopile and increasing the thickness of the thermal resistance layer, the high-sensitivity thin-film thermopile heat flux meter of the present invention improves the sensitivity of the heat flux meter sensor to heat flux density measurement by providing a thermal resistance layer above the cold node, eliminating the need for signal amplification processing. The present invention utilizes thin-film technology and has the advantages of simple structure, fast response speed, wide measurement temperature range, and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0027] Figure 1 is a cross-sectional schematic diagram of a high-sensitivity thin-film thermopile type heat flow meter according to an embodiment of the present invention;

[0028] Figure 2 Schematic top view of a high-sensitivity thin-film thermopile type heat flow meter according to an embodiment of the present invention;

[0029] Figure 3 is the response time of the thin film heat flux meter under pulse excitation in the embodiment of the present invention.

[0030] In the figure: 1 is the lower thermal resistance layer, 2 is the positive thermocouple, 3 is the upper thermal resistance layer, 4 is the negative thermocouple, 5 is the base, 6 is the hot node, 7 is the cold node, 8 is the positive thermopile lead end, and 9 is the negative thermopile lead end. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0032] In order to solve the technical problem of simultaneous measurement of temperature and heat flux, the present invention uses thin film technology to produce a thermopile type transient temperature and heat flux joint measurement sensor. The sensor of the present invention inherits the simple measurement principle and method of temperature and can also use thin film technology to measure transient heat flux. Figure 1-2As shown, an embodiment of the present invention provides a high-sensitivity thin-film thermopile type heat flux meter, which includes: a substrate 5, a lower thermal resistance layer 1, a thermopile thin film and an upper thermal resistance layer 3. The substrate 5 is preferably a ceramic substrate. The ceramic substrate has high temperature resistance and good thermal matching with the oxide thermal resistance layer. The lower thermal resistance layer 1 is arranged on the substrate. The thermopile thin film formed by overlapping a plurality of pairs of thermocouples is arranged on the lower thermal resistance layer 1 to increase the output potential of the thermopile. Each pair of thermocouples is formed by a positive thermocouple 2 and a negative thermocouple 4 connected in series. The positive thermocouple 2 and the negative thermocouple 4 are connected in a stepped manner. Due to the ductility of metal, the thermocouple 2 is connected to the negative thermocouple 4 in a stepped manner. , can be connected without breaking, thereby improving sensitivity; the lower thermal resistance layer 1 covers below the hot node 6 where the positive thermocouple 2 is connected to the negative thermocouple 4; the upper thermal resistance layer 3 is provided on the thermopile film, and the upper thermal resistance layer 3 covers above the cold node 7 where the positive thermocouple 2 is connected to the negative thermocouple 4, so as to increase the measurement range and improve the measurement accuracy; one end of the thermopile film is provided with a positive thermopile lead terminal 8 for connection, and the other end of the thermopile film is provided with a negative thermopile lead terminal 9 for connection, and the two ends of the thermopile film are connected through the positive thermopile lead terminal 8 and the negative thermopile lead terminal 9 respectively. The thermopile film also has a temperature measurement function, such as Figure 2 As shown, the negative thermopile lead 9 and the positive thermopile lead end 8 are connected to each other to form a thermocouple, and the temperature signal can be measured through the leads.

[0033] In this embodiment, there is a certain height difference between the cold node 7 and the hot node 6 connecting the positive thermocouple 2 and the negative thermocouple 4 . The hot node 6 is above the lower thermal resistance layer 1 , and the cold node 7 is below the upper thermal resistance layer 3 . When the external environment applies a vertical heat flow to the thin film thermopile type heat flux meter, the hot node 6 is in direct contact with the heat flow, while the thermal resistance layer below prevents heat loss; the thermal resistance layer above the cold node 7 prevents heat transfer, while the substrate 5 below promptly conducts the heat away. As a result, a temperature difference exists between the cold node 7 and the hot node 6 of the thin film thermopile. According to the Seebeck effect, a corresponding potential difference is generated at both ends of the thin film thermopile. The two ends of the thin film thermopile are respectively connected through the positive thermopile lead terminal 8 and the negative thermopile lead terminal 9. The output potential of the positive thermopile lead terminal 8 and the negative thermopile lead terminal 9 is related to the heat flux density, thereby realizing synchronous transient measurement of temperature and heat flux density; at the same time, this structure makes the temperature difference between the cold node 7 and the hot node 6 larger, which is conducive to improving sensitivity; the thin film thermopile type heat flux meter of the embodiment of the present invention has the characteristics of simple structure, fast response speed, wide measurement temperature range, high measurement accuracy, and high sensitivity.

[0034] This embodiment utilizes multiple pairs of positive thermocouples 2 and negative thermocouples 4 connected in series to form a thermopile, and increases the thickness of the thermal resistance layer to improve the sensor's sensitivity to heat flux measurements, eliminating the need for signal amplification. In some preferred embodiments, the thickness of the upper thermal resistance layer 3 is 2-5 microns, the thickness of the lower thermal resistance layer 1 is 2-5 microns, and the number of thermocouple pairs in the thermopile film is selected from 20 to 160, with the specific number of thermocouple pairs determined based on sensitivity requirements.

[0035] In order to improve the stability of the thermocurrent sensor at high temperature, in this embodiment, the thin film thermopile is composed of PtRh-Pt type thermocouples or Pt-ITO thermocouples connected in series, and can also be composed of ITO-In2O3 type thermocouples, WRe x -WRe y Type thermocouple such as WRe3-WRe 25 Thermocouple, WRe5-WRe 26 Thermocouples, etc.; or K-type thermocouples (nickel-chromium-nickel-silicon thermocouples) are connected in series.

[0036] To ensure the thermocurrent sensor maintains excellent stability at high temperatures, in one specific embodiment, when the thermopile thin film is composed of PtRh-Pt thermocouples connected in series, the positive thermocouple 2 and the positive thermopile lead terminal 8 are both deposited using magnetron sputtering and patterned using mask sputtering or lift-off techniques. The positive thermocouple 2 and the positive thermopile lead terminal 8 are made of the same material, platinum-rhodium; the negative thermocouple 4 and the negative thermopile lead terminal 9 are made of the same material, platinum. The same applies when the thermopile thin film is composed of other types of thermocouples connected in series.

[0037] To ensure that the thermocurrent sensor maintains good stability at high temperatures, the leads of the positive thermopile lead terminal 8 and the negative thermopile lead terminal 9 are made of two different metal wire materials. For example, in one specific embodiment, the metal wire material of the lead of the positive thermopile lead terminal 8 is platinum wire or platinum-rhodium wire, and the metal wire material of the lead of the negative thermopile lead terminal 9 is platinum or ITO.

[0038] The upper and lower thermal resistance layers 3 and 4 are made of the same material. To expand the temperature measurement range, the materials for the upper and lower thermal resistance layers 3 and 1 are selected from polyimide (PI), silicon dioxide (SiO2), or YSZ (yttria-stabilized zirconia), depending on the operating environment. However, the thickness can vary depending on the requirements. In low-temperature operating environments (up to 350°C), both the upper and lower thermal resistance layers 3 and 1 are made of polyimide. In high-temperature operating environments (over 350°C), both the upper and lower thermal resistance layers 3 and 1 are made of silicon dioxide or YSZ. Using these materials for the thermal resistance layers not only provides excellent thermal insulation but also serves as a protective layer for the heat flow meter to prevent oxidation.

[0039] The method for preparing a high-sensitivity thin-film thermopile type heat flow meter according to an embodiment of the present invention comprises:

[0040] S1. Provide a substrate. The substrate is preferably a ceramic substrate. The ceramic substrate has high temperature resistance and good thermal compatibility with the oxide thermal resistance layer. Form a thin film on the substrate and pattern it using a mask sputtering method or a stripping method to form a lower thermal resistance layer. To achieve good thermal insulation and expand the temperature measurement range, the material of the lower thermal resistance layer is selected from polyimide (PI), SiO2, or YSZ according to the working environment. In a low-temperature working environment with a temperature not exceeding 350°C, the material of the lower thermal resistance layer is polyimide. Specifically, the film can be formed by suspension coating of polyimide. In a high-temperature working environment with a temperature exceeding 350°C, the material of the lower thermal resistance layer is silicon dioxide or YSZ. Specifically, the silicon dioxide can be formed by dual ion beam sputtering. The selection of these two materials can also prevent oxidation.

[0041] In order to improve the sensitivity of the sensor to heat flux density measurement, in some embodiments, the thickness of the lower thermal resistance layer is 2-5 microns.

[0042] S2. A thin film is deposited on the lower thermal resistance layer by magnetron sputtering, and patterned by mask sputtering or stripping to form a positive thermocouple thin film array and a positive thermopile lead end on the substrate; when the thermopile film is composed of PtRh-Pt type thermocouples in series, the positive thermocouple and the positive thermopile lead end are made of the same material, both of which are platinum-rhodium; when the thermopile film is composed of Pt-ITO thermocouples in series, the materials of the positive thermocouple and the positive thermopile lead end are both platinum; when the thermopile film is WRe x -WRe y When the type thermocouples are connected in series, the materials of the positive thermocouple and the positive thermopile lead end are WRe xWhen the thermopile film is composed of ITO-In2O3 type thermocouples in series, the materials of the positive thermocouple and the positive thermopile lead end are both ITO; when the thermopile film is composed of K-type thermocouples in series, the materials of the positive thermocouple and the positive thermopile lead end are both nickel-chromium; thereby ensuring that the thermal current sensor maintains good stability at high temperatures.

[0043] S3. A thin film is deposited on the positive thermocouple film array by magnetron sputtering, and patterned by mask sputtering or stripping to form a negative thermocouple film array and a negative thermopile lead end. A positive thermocouple and a negative thermocouple are connected in series to form a pair of thermocouples. Several pairs of thermocouples are overlapped end to end to form a thermopile film. The positive thermocouple and the negative thermocouple are connected in a step-like manner. The lower thermal resistance layer covers the bottom of the hot node where the positive thermocouple and the negative thermocouple are connected. When the thermopile film is composed of PtRh-Pt type thermocouples connected in series, the negative thermocouple and the negative thermopile lead end are made of the same material, both of which are platinum. When the thermopile film is composed of Pt-ITO thermocouples connected in series, the negative thermocouple and the negative thermopile lead end are made of the same material, both of which are ITO. When the thermopile film is WRe x -WRe y When the type thermocouples are connected in series, the negative thermocouple 4 and the negative thermopile lead end 9 are made of WRe y When the thermopile film is composed of ITO-In2O3 type thermocouples in series, the materials of the negative thermocouple 4 and the negative thermopile lead end 9 are both In2O3; when the thermopile film is composed of K-type thermocouples in series, the materials of the negative thermocouple 4 and the negative thermopile lead end 9 are both nickel silicon; thereby ensuring that the thermal current sensor maintains good stability at high temperatures.

[0044] In order to improve the sensitivity of the sensor to heat flux density measurement, in some embodiments, the number of thermocouple pairs in the thermopile film is 20-160 pairs.

[0045] S4. A thin film is formed on the negative thermocouple thin film array, and patterned by a mask sputtering method or a stripping method to form an upper thermal resistance layer. The upper thermal resistance layer covers the cold node where the positive thermocouple and the negative thermocouple are connected. In order to achieve a good thermal insulation effect and expand the temperature measurement range, the material of the upper thermal resistance layer is selected from polyimide (PI), SiO2, or YSZ according to the working environment. In a low-temperature working environment with a temperature not exceeding 350°C, the material of the upper thermal resistance layer is polyimide. Specifically, the film can be formed by suspended coating of polyimide. In a high-temperature working environment with a temperature exceeding 350°C, the material of the upper thermal resistance layer is silicon dioxide or YSZ. Specifically, the film can be formed by double ion beam sputtering of silicon dioxide. The selection of these two materials can also prevent oxidation.

[0046] In order to improve the sensitivity of the sensor to heat flux density measurement, in some embodiments, the thickness of the lower thermal resistance layer is 2-5 microns.

[0047] In order to illustrate the technical effect of the heat flow meter in the embodiment of the present invention, Figure 3 The response time test results of a thin film heat flow meter using a Pt-PtRh thin film as a thermopile and a 2-micron thick silicon oxide as a thermal resistance layer are shown. Figure 3 It can be seen that under the excitation of the pulsed laser heat source, the response time of this thin film thermopile type heat flux sensor is measured to be 0.07ms, which shows that this thin film heat flux meter can be used for transient heat flux measurement.

[0048] The present invention utilizes thin film technology, boasting small size and fast response speed, and is capable of measuring transient heat flux density. Multiple pairs of thermocouples are overlapped end-to-end to form a thin film thermopile, with the two ends of the thermopile thin film connected via positive and negative thermopile lead terminals, respectively. This allows for temperature measurement, and through the influence of the thermal resistance layer, heat flux density can also be measured, thereby enabling simultaneous transient measurement of temperature and heat flux density. Furthermore, the thin film thermopile heat flux meter of the present invention utilizes a unique structure in which a lower thermal resistance layer is provided below the hot node and an upper thermal resistance layer is provided above the cold node, thereby increasing the temperature difference between the two ends and enhancing the sensor's sensitivity to heat flux density measurement. Furthermore, the thin film thermopile heat flux meter of the present invention achieves the purpose of enhancing the sensor's sensitivity to heat flux density measurement by increasing the number of thermocouples in the thin film thermopile and increasing the thickness of the thermal resistance layer, eliminating the need for signal amplification. The meter has the advantages of a simple structure, fast response speed, a wide measurement temperature range, and high sensitivity.

[0049] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various modifications or variations within the scope of the claims without affecting the essence of the present invention. The above preferred features may be used in any combination as long as they do not conflict with each other.

Claims

1. A high-sensitivity thin-film thermopile type heat flow meter, characterized in that: include: substrate; a lower thermal resistance layer, disposed on the substrate; A thermopile thin film formed by overlapping multiple pairs of thermocouples end to end is provided on the lower thermal resistance layer, wherein each pair of thermocouples is formed by a positive thermocouple and a negative thermocouple connected in series, and the positive thermocouple and the negative thermocouple are connected in a stepped manner; the lower thermal resistance layer covers below the hot node where the positive thermocouple and the negative thermocouple are connected; an upper thermal resistance layer, provided on the thermopile film, wherein the upper thermal resistance layer covers the cold node where the positive thermocouple and the negative thermocouple are connected; One end of the thermopile film is provided with a positive thermopile lead end for connection, and the other end of the thermopile film is provided with a negative thermopile lead end for connection; the thermopile film also has a temperature measurement function, the negative thermopile lead and the positive thermopile lead end are interconnected to form a thermocouple, and the temperature signal is measured through the leads.

2. A high-sensitivity thin film thermopile type heat flow meter according to claim 1, characterized in that: The upper thermal resistance layer and the lower thermal resistance layer are made of the same material.

3. The high-sensitivity thin film thermopile type heat flow meter according to claim 1, characterized in that: The thickness of the upper thermal resistance layer is 2-5 microns, and the thickness of the lower thermal resistance layer is 2-5 microns.

4. The high-sensitivity thin film thermopile type heat flow meter according to claim 1, characterized in that: The thermopile film is composed of PtRh-Pt type thermocouple, Pt-ITO type thermocouple, WRe x -WRe y It is composed of any one of type thermocouple, ITO-In2O3 type thermocouple and K type thermocouple connected in series.

5. The high-sensitivity thin film thermopile type heat flow meter according to claim 4, characterized in that: When the thermopile film is a PtRh-Pt type thermocouple connected in series, the materials of the positive thermocouple and the positive thermopile lead end are both platinum-rhodium, and the materials of the negative thermocouple and the negative thermopile lead end are both platinum; When the thermopile film is a Pt-ITO type thermocouple connected in series, the material of the positive thermocouple and the positive thermopile lead end are both Pt, and the material of the negative thermocouple and the negative thermopile lead end are both ITO; When the thermopile film is WRe x -WRe y When the positive thermocouple is connected in series, the material of the positive thermocouple and the positive thermopile lead end are both WRe x The negative electrode thermocouple and the negative electrode thermopile lead end are made of WRe y ; When the thermopile film is formed by connecting ITO-In2O3 type thermocouples in series, the materials of the positive thermocouple and the positive thermopile lead end are both ITO, and the materials of the negative thermocouple and the negative thermopile lead end are both In2O3; When the thermopile film is formed by K-type thermocouples connected in series, the materials of the positive thermocouple and the positive thermopile lead end are both nickel-chromium, and the materials of the negative thermocouple and the negative thermopile lead end are both nickel-silicon.

6. The high-sensitivity thin film thermopile type heat flow meter according to claim 1, characterized in that: The number of thermocouple pairs in the thermopile film ranges from 20 to 160 pairs.

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