A high irradiance heat flux sensor calibration device and calibration method

Abstract

The present invention discloses a high-irradiance heat flux sensor calibration device and calibration method, comprising: a laser, an aspheric lens group system is arranged inside the laser; a 4f imaging system is arranged in the laser emission direction of the collimating lens; a primary spectroscopic module; a secondary spectroscopic module; a photodetector; a feeding platform, on which a standard heat flux sensor and a heat flux sensor to be calibrated are clamped; a camera is arranged on another spectroscopic optical path of the secondary spectroscopic module, the camera is connected to a measurement and control computer through a cable, and the laser, the photodetector and the feeding platform are connected to the measurement and control computer through a cable. The high-irradiance heat flux sensor calibration device provided by the present invention adopts a high-power and high-uniformity optical fiber laser, and uses a 4f system to perform secondary homogenization and shaping on the light beam, thereby obtaining a stable, uniform, and continuously adjustable laser heat source, and based on this light source, a comparison calibration method is adopted to realize the calibration and response time measurement of an extremely high heat flux sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of extremely high heat flux sensor calibration, and more specifically, the present invention relates to a high irradiance heat flux sensor calibration device and a calibration method. Background Art

[0002] Hypersonic vehicles will be subjected to severe aerodynamic heating when flying at high speed in the atmosphere. When simulating this heating process in ground heat protection tests, it is necessary to first use a heat flux sensor to measure the accurate heat flux value of the calibration model. As the Mach number of the aircraft increases, the heat flux that needs to be simulated also increases rapidly. In order to obtain the extremely high heat flux (30MW / m 2 In order to obtain the accurate value of the heat flux sensor (above), the heat flux sensor used must be calibrated, and the heat flux sensor calibration device needs to cover the measured heat flux range. The heat flux sensor calibration coefficient obtained in this way will be more accurate than the linear extrapolation method, so there is an urgent need for such a calibration device for extremely high heat flux. Summary of the invention

[0003] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0004] In order to achieve these purposes and other advantages according to the present invention, a high irradiance thermal flux sensor calibration device is provided, comprising:

[0005] A laser, wherein an aspheric lens group system is arranged inside the laser, wherein the aspheric lens group system comprises an aspheric lens and a collimating lens close to the laser light source;

[0006] A 4f imaging system is arranged in the laser emission direction of the collimating lens; a primary light splitting module is aligned with the emission port of the 4f imaging system; and a secondary light splitting module is aligned with a light splitting path of the primary light splitting module;

[0007] A photoelectric detector is positioned to align with one of the split light paths of the secondary split light module; a feeding platform is positioned to align with another split light path of the primary split light module, and a standard heat flux sensor and a heat flux sensor to be calibrated are clamped on the feeding platform; a camera is arranged on another of the split light paths of the secondary split light module, and the camera is connected to a measurement and control computer via a cable, and the laser, the photoelectric detector and the feeding platform are connected to the measurement and control computer via a cable.

[0008] Preferably, the laser generates a laser beam with a Gaussian distribution of irradiance, and the aspheric lens group system shapes the laser beam with a Gaussian distribution of irradiance into a uniform beam, that is, the incident laser beam is first modulated by the aspheric lens of the aspheric lens group system, and then a nearly flat-top beam with uniform irradiance distribution is obtained at the collimating lens position.

[0009] Preferably, the laser is a high-power fiber laser;

[0010] The primary light splitting module and the secondary light splitting module are light splitting lenses.

[0011] Preferably, the structure of the feeding platform includes:

[0012] A fixed base, on which three parallel longitudinal guide rails are fixedly arranged; a slider I is slidably arranged on the longitudinal guide rail, and a transverse guide rail is integrally formed on the slider I; a slider II is slidably arranged on the transverse guide rail, and a plurality of sensor fixtures are fixedly arranged on the slider II;

[0013] A stepper motor I, which is fixedly arranged on one side of the fixed base, wherein the output shaft of the stepper motor I is fixedly connected to a screw rod I, a ball screw nut I is fixedly arranged in the slider I, and the ball screw nut I is sleeved on the screw rod I;

[0014] The stepper motor II is fixedly arranged on one side of the transverse guide rail, the output shaft of the stepper motor II is fixedly connected with a screw rod II, the slider II is fixedly provided with a ball nut II, and the ball nut II is sleeved on the screw rod II.

[0015] Preferably, the 4f imaging system comprises lens I and lens II fixed by a bracket, wherein lens I is located between lens II and the laser.

[0016] A high irradiance heat flux sensor calibration method comprises the following steps:

[0017] Step 1: Install the standard heat flow sensor and the heat flow sensor to be calibrated on the feeding platform, and use the sensor fixture to clamp and fix the standard heat flow sensor and the heat flow sensor to be calibrated respectively; check all water connections and line connections, and turn on the laser after confirming that there are no problems;

[0018] Step 2: Check the beam distribution data collected by the camera. If the beam distribution satisfies the unevenness less than 3%, proceed to step 3. Otherwise, the optical path system needs to be adjusted. The exposure time of the laser is set according to the effective test time of different types of heat flux sensors.

[0019] Step 3: Align the standard heat flux sensor with the main optical path of the primary spectrometer module, use the standard heat flux sensor to detect the spot irradiance, that is, the heat flux density, and adjust the laser power to P. At this time, the heat flux density measured by the standard heat flux sensor is q std Temporarily turn off the laser, align the heat flux sensor to be calibrated with the main optical path of the primary light splitting module, set the laser power value P to be the same as that of the standard heat flux sensor, and then turn on the laser to obtain the calorific value q of the heat flux sensor to be calibrated test ;

[0020] Step 4: Repeat step 3 5 times, and set the power value that fails each time as needed, and then you can get X={0,q test1 ,q test2 ,q test3 ,q test4 ,q test5}, Y = {0, q std1 ,q std2 ,q std3 ,q std4 ,q std5}, then take the value of X as the independent variable and the value of Y as the dependent variable for linear fitting, and the slope η after fitting is the calibration coefficient of the heat flow sensor to be calibrated;

[0021] Step 5. At the same time, according to the test needs, the response time of the heat flow sensor to be calibrated can be evaluated with the help of the step signal collected by the photoelectric detector.

[0022] Preferably, in the step three, the method for aligning the standard heat flux sensor or the heat flux sensor to be calibrated with the main light path of the first-level spectrometer module is: turning on the stepper motor II, and the stepper motor II drives the screw rod II to rotate, so that the slider II moves laterally along the transverse guide rail, so that the standard heat flux sensor or the heat flux sensor to be calibrated clamped on the sensor fixture can be aligned with the main light path of the first-level spectrometer module; at the same time, by turning on the stepper motor I, the longitudinal position of the standard heat flux sensor and the heat flux sensor to be calibrated can be adjusted.

[0023] The present invention has at least the following beneficial effects: the high irradiance heat flux sensor calibration device provided by the present invention adopts a high-power and high-uniformity fiber laser, and uses a 4f system to perform secondary homogenization and shaping of the light beam, thereby obtaining a stable, uniform, and continuously adjustable laser heat source. Based on this light source, a comparison calibration method is used to achieve a 50MW / m 2 The calibration and response time measurement of extremely high heat flux sensors within the range of 10000 to 20000 ℃ fills the gap in the calibration of ultra-high heat flux levels of domestic heat flux sensors.

[0024] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of a high irradiance heat flux sensor calibration device according to a preferred embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the structure of the feeding platform provided by the present invention;

[0027] Figure 3 A schematic diagram of the structure of the aspheric lens assembly system provided by the present invention;

[0028] Figure 4 This is a schematic diagram of the imaging principle of the 4f imaging system provided by the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0030] It should be understood that terms such as “having”, “including” and “comprising” used herein do not specify the existence or addition of one or more other elements or combinations thereof.

[0031] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the term is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, in the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0034] like Figure 1-4 As shown: A high irradiance heat flux sensor calibration device of the present invention comprises:

[0035] A laser 1, in which an aspheric lens group system is arranged, wherein the aspheric lens group system comprises an aspheric lens F1 close to the laser light source and a collimating lens F2;

[0036] 4f imaging system 2, which is arranged in the laser emission direction of the collimating lens F2; ​​a primary light splitting module 3, which is aligned with the emission port of 4f imaging system 2; a secondary light splitting module 4, which is aligned with a light splitting path of the primary light splitting module 3;

[0037] A photoelectric detector 5 is positioned to align with one of the split light paths of the secondary split light module 4; a feeding platform 6 is positioned to align with another split light path of the primary split light module 3, and a standard heat flux sensor and a heat flux sensor to be calibrated are clamped on the feeding platform 6; a camera 7 is arranged on another split light path of the secondary split light module 4, and the camera 7 is connected to a measurement and control computer 8 via a cable, and the laser 1, the photoelectric detector 5 and the feeding platform 6 are connected to the measurement and control computer 8 via a cable.

[0038] Working principle: The laser 1 generates a laser beam with a Gaussian irradiance distribution. The aspheric lens group system shapes the laser beam with a Gaussian irradiance distribution into a uniform beam, that is, the incident laser beam is first modulated by the aspheric lens F1 of the aspheric lens group system, and then a nearly flat-top beam with uniform irradiance distribution is obtained at the position of the collimating lens F2. The collimating lens F2 has two functions. One is to collimate the relatively uniform nearly flat-top beam into parallel light. The second function is that the outgoing beam will have a certain light mixing effect during the collimation process. At a specific working distance (BFL of the collimating lens F2), the nearly flat-top light will be further homogenized to obtain a flat-top light that meets the unevenness index. The power of the laser 1 is continuously adjustable, and the output beam is required to have good uniformity; after the beam comes out of the laser 1, it enters the 4f imaging system 2, the primary spectrometer module 3, the secondary spectrometer module 4, the feeding platform 6, the camera 7 and the photoelectric detector 5 in turn. The 4f imaging system 2 can realize one-to-one corresponding wavefront transmission, and can project the homogenized light spot to a specified distance, while shaping the spot diameter into the required spot size. Therefore, the 4f imaging system 2 is used to perform secondary homogenization on the light beam and expand and contract the beam diameter, so that the final unevenness of the light beam and the spot size meet the use requirements. Due to the extremely high power density of the light beam, it is necessary to consider the thermal disturbance of the 4f imaging system 2 during imaging, and to select the appropriate focal length of the two lenses in the 4f imaging system in combination with the spot size requirements and the spot distance requirements. The first-level spectroscopic module 3 allows most of the light energy to enter the standard heat flux sensor and the heat flux sensor to be calibrated on the delivery platform 6. During the specific calibration, the specific position of the standard heat flux sensor or the heat flux sensor to be calibrated can be moved to align the laser beam. The splitting ratio of the primary splitting module 3 and the secondary splitting module 4 needs to be set according to the safety threshold of the beam receiving instrument of the main light path and the splitting path. The beam entering the feeding platform 6 is the main light path, and the beam entering the camera 7 and the photodetector 5 is the splitting path. According to the safety threshold of the response sensitivity of the beam receiver of the splitting path, the splitting ratio of the primary splitting module and the secondary splitting module is adjusted to ensure that the beam receiver can detect the weak light irradiation of the splitting path and the beam receiver is not burned by the laser. The camera 7 is used to detect the unevenness of the light beam. The photodetector 5 is used to detect the frequency response characteristics of the light beam. The measurement and control computer 8 is respectively connected to the laser 1, the feeding platform 6, the standard heat flux sensor, the heat flux sensor to be calibrated, the camera 7 and the photodetector 5, and is used to control the beam output of the laser 1 and the movement of the feeding platform 6 and collect the output signals of the camera 7, the photodetector 5, the standard heat flux sensor and the heat flux sensor to be calibrated. The high-irradiance heat flux sensor calibration device provided by the present invention adopts a high-power and high-uniformity optical fiber laser, and uses a 4f system to perform secondary homogenization and shaping on the light beam, thereby obtaining a stable, uniform, and continuously adjustable laser heat source.

[0039] In the above technical solution, the laser 1 is a high-power fiber laser, and an aspheric lens group system is used to perform homogenization on the transmission path from the fiber light source to the fiber head. The light beam coming out of the fiber head already has a laser wavefront that meets the uniformity index;

[0040] The primary light splitting module 3 and the secondary light splitting module 4 are light splitting lenses.

[0041] In the above technical solution, the structure of the feeding platform includes:

[0042] A fixed base 9, on which three parallel longitudinal guide rails 10 are fixedly arranged; a slider I 11 is slidably arranged on the longitudinal guide rail 10, and a transverse guide rail 12 is integrally formed on the slider I 11; a slider II 13 is slidably arranged on the transverse guide rail 12, and two sensor fixtures 14 are fixedly arranged on the slider II 13, respectively used to fix the standard heat flow sensor and the heat flow sensor to be calibrated;

[0043] A stepper motor Ⅰ15 is fixedly arranged on one side of the fixed base 9, the output shaft of the stepper motor Ⅰ15 is fixedly connected to a screw rod Ⅰ16, a ball nut Ⅰ17 is fixedly arranged in the slider Ⅰ11, and the ball nut Ⅰ17 is sleeved on the screw rod Ⅰ16;

[0044] The stepper motor II18 is fixedly arranged on one side of the transverse guide rail 12, and the output shaft of the stepper motor II18 is fixedly connected with a screw rod II19, and the slider II13 is fixedly provided with a ball screw nut II20, and the ball screw nut II20 is sleeved on the screw rod II19. When the stepper motor II18 is turned on, the stepper motor II18 drives the screw rod II19 to rotate, so that the slider II13 moves laterally along the transverse guide rail 12, and the standard heat flux sensor or the heat flux sensor to be calibrated clamped on the sensor fixture 14 can be aligned with the main optical path of the primary spectrometer module 3; at the same time, by turning on the stepper motor I15, the stepper motor I15 drives the screw rod I16 to rotate, so that the slider I11 moves longitudinally along the longitudinal guide rail 10, and the longitudinal position of the standard heat flux sensor and the heat flux sensor to be calibrated can be adjusted.

[0045] In the above technical solution, the 4f imaging system 2 includes a lens IF3 and a lens IIF4 fixed by a bracket, wherein the lens IF3 is located between the lens IIF4 and the laser 1. Figure 4 As shown, A is a uniform light spot that has met the homogenization index. This uniform light spot surface can be transferred to a specified distance through the real focus 4f system 2 composed of lens IF3 and lens IF4 to form a smaller light spot B that also meets the homogenization index.

[0046] A high irradiance heat flux sensor calibration method comprises the following steps:

[0047] Step 1: Install the standard heat flow sensor and the heat flow sensor to be calibrated on the feeding platform 6, and use the sensor fixture 14 to clamp and fix the standard heat flow sensor and the heat flow sensor to be calibrated respectively; check all water connections and line connections, and turn on the laser 1 after confirming that there is no problem;

[0048] Step 2: Check the beam distribution data collected by the camera 7. If the beam distribution satisfies the unevenness less than 3%, proceed to step 3. Otherwise, the optical path system needs to be adjusted. The exposure time of the laser 1 is set according to the effective test time of different types of heat flux sensors.

[0049] Step 3: Align the standard heat flux sensor with the main optical path of the primary light splitting module 3, use the standard heat flux sensor to detect the spot irradiance, that is, the heat flux density, and adjust the power of the laser 1 to P. At this time, the heat flux density measured by the standard heat flux sensor is q std Temporarily turn off the laser, align the heat flux sensor to be calibrated with the main optical path of the primary light splitting module 3, set the laser power value P to be the same as that of the standard heat flux sensor, and then turn on the laser 1 to obtain the calorific value q of the heat flux sensor to be calibrated test ;

[0050] Step 4: Repeat step 3 5 times, and set the power value that fails each time as needed, and then you can get X={0,q test1 ,q test2 ,q test3 ,q test4 ,q test5}, Y = {0, q std1 ,q std2 ,q std3 ,q std4 ,q std5}, then use the value of X as the independent variable and the value of Y as the dependent variable for linear fitting. The slope η after fitting is the calibration coefficient of the heat flow sensor to be calibrated. When calibrating a zero-point calorimeter, we get: X = {0, 1.201, 2.046, 3.035, 4.153, 5.43}, Y = {0, 1.117, 1.954, 2.908, 3.959, 5.144}, all in MW / m 2 , then the linear fitting can obtain its calibration coefficient as 0.9503;

[0051] Step 5: At the same time, according to the test requirements, the response time of the heat flow sensor to be calibrated can be evaluated with the help of the step signal collected by the photoelectric detector 5 .

[0052] In summary, the high-irradiance heat flux sensor calibration device provided by the present invention adopts a high-power and high-uniformity fiber laser, and uses the 4f system to perform secondary homogenization and shaping of the light beam, thereby obtaining a stable, uniform, and continuously adjustable laser heat source. Based on this light source, the comparison calibration method is used to realize the calibration and response time measurement of extremely high heat flux sensors within 50MW / m2.

[0053] In the above technical scheme, the method for aligning the standard heat flux sensor or the heat flux sensor to be calibrated with the main light path of the first-level spectrometer module 3 in step three is: turn on the stepper motor II18, and the stepper motor II18 drives the screw rod II19 to rotate, so that the slider II13 moves laterally along the transverse guide rail 12, and the standard heat flux sensor or the heat flux sensor to be calibrated clamped on the sensor fixture 14 can be aligned with the main light path of the first-level spectrometer module 3; at the same time, by turning on the stepper motor I15, the stepper motor I15 drives the screw rod I16 to rotate, so that the slider I11 moves longitudinally along the longitudinal guide rail 10, and the longitudinal position of the standard heat flux sensor and the heat flux sensor to be calibrated can be adjusted.

[0054] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

[0055] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for calibrating a high irradiance heat flux sensor, characterized in that: The high irradiance heat flux sensor calibration device used includes: A laser, wherein an aspheric lens group system is arranged inside the laser, wherein the aspheric lens group system comprises an aspheric lens and a collimating lens close to the laser light source; A 4f imaging system is arranged in the laser emission direction of the collimating lens; a primary light splitting module is aligned with the emission port of the 4f imaging system; and a secondary light splitting module is aligned with a light splitting path of the primary light splitting module; A photoelectric detector is aligned with one of the split light paths of the secondary split light module; a feeding platform is aligned with another split light path of the primary split light module, and a standard heat flux sensor and a heat flux sensor to be calibrated are clamped on the feeding platform; a camera is arranged on another split light path of the secondary split light module, and the camera is connected to a measurement and control computer via a cable, and the laser, the photoelectric detector and the feeding platform are connected to the measurement and control computer via a cable; The method for calibrating a high irradiance heat flux sensor comprises the following steps: Step 1: Install the standard heat flow sensor and the heat flow sensor to be calibrated on the feeding platform, and use the sensor fixture to clamp and fix the standard heat flow sensor and the heat flow sensor to be calibrated respectively; check all water connections and line connections, and turn on the laser after confirming that there are no problems; Step 2: Check the beam distribution data collected by the camera. If the beam distribution satisfies the unevenness less than 3%, proceed to step 3. Otherwise, the optical path system needs to be adjusted. The exposure time of the laser is set according to the effective test time of different types of heat flux sensors. Step 3: Align the standard heat flux sensor to the main optical path of the primary spectrometer module, use the standard heat flux sensor to detect the spot irradiance, that is, the heat flux density, and adjust the laser power to P At this time, the heat flux density measured by the standard heat flux sensor is q std ; Temporarily turn off the laser, align the heat flux sensor to be calibrated with the main optical path of the primary light splitting module, and then set the laser power value to the same as the standard heat flux sensor P , then turn on the laser to obtain the calorimetric value of the heat flux sensor to be calibrated q test ; Step 4: Repeat step 3 5 times, setting different power values ​​each time as needed, and then you can get X={0, q test1 , q test2 , q test3 , q test4 , q test5 },Y={0, q std1 , q std2 , q std3 , q std4 , q std5 }, then use the value of X as the independent variable and the value of Y as the dependent variable to perform a linear fit. The slope after fitting is η That is the calibration coefficient of the heat flow sensor to be calibrated; Step 5. At the same time, in combination with the test needs, the response time of the heat flow sensor to be calibrated is evaluated using the step signal collected by the photoelectric detector.

2. The method for calibrating a high irradiance thermal flux sensor according to claim 1, characterized in that: The laser generates a laser beam with a Gaussian irradiance distribution, and the aspheric lens group system shapes the laser beam with a Gaussian irradiance distribution into a uniform beam, that is, the incident laser beam is first modulated by the aspheric lens of the aspheric lens group system, and then a nearly flat-top beam with uniform irradiance distribution is obtained at the collimating lens position.

3. The method for calibrating a high irradiance thermal flux sensor according to claim 1, characterized in that: The laser is a high-power fiber laser; The primary light splitting module and the secondary light splitting module are light splitting lenses.

4. The method for calibrating a high irradiance thermal flux sensor according to claim 1, characterized in that: The structure of the feeding platform comprises: A fixed base, on which three parallel longitudinal guide rails are fixedly arranged; a slider I is slidably arranged on the longitudinal guide rail, and a transverse guide rail is integrally formed on the slider I; a slider II is slidably arranged on the transverse guide rail, and a plurality of sensor fixtures are fixedly arranged on the slider II; A stepper motor I, which is fixedly arranged on one side of the fixed base, wherein the output shaft of the stepper motor I is fixedly connected to a screw rod I, a ball screw nut I is fixedly arranged in the slider I, and the ball screw nut I is sleeved on the screw rod I; The stepper motor II is fixedly arranged on one side of the transverse guide rail, the output shaft of the stepper motor II is fixedly connected with a screw rod II, the slider II is fixedly provided with a ball nut II, and the ball nut II is sleeved on the screw rod II.

5. The method for calibrating a high irradiance thermal flux sensor according to claim 1, characterized in that: The 4f imaging system comprises a lens I and a lens II fixed by a bracket, wherein the lens I is located between the lens II and the laser.

6. The method for calibrating a high irradiance thermal flux sensor according to claim 1, characterized in that: The method for aligning the standard heat flux sensor or the heat flux sensor to be calibrated with the main optical path of the primary spectrometer module in the step three is: turning on the stepper motor II, and the stepper motor II drives the screw rod II to rotate, so that the slider II moves laterally along the transverse guide rail, so that the standard heat flux sensor or the heat flux sensor to be calibrated clamped on the sensor fixture can be aligned with the main optical path of the primary spectrometer module; at the same time, by turning on the stepper motor I, the longitudinal position of the standard heat flux sensor and the heat flux sensor to be calibrated can be adjusted.

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