JP4953061B2 - Object heating method and apparatus - Google Patents

Description

  In particular, the present invention is a method for heating an object, and a device for carrying out the method, capable of maintaining a constant temperature at a predetermined temperature with good reproducibility and efficiency when various materials are heated to a predetermined temperature at a high speed and then maintained at a constant temperature. Further, the present invention relates to a method and apparatus using the same object heating method and apparatus.

  In order to perform heat transfer analysis of equipment that generates heat and equipment that is used at high temperatures, the thermal property values related to the transfer and accumulation of heat (specific heat capacity, hemispherical emissivity, heat conductivity, heat Diffusion rate) is required. When a newly developed material or a material that does not have a reliable accumulation of literature values is used as a constituent material of the device, the above-mentioned thermophysical property value needs to be obtained experimentally. In general, the above four thermophysical values are measured by different devices, so that there is a problem that costs and time are superimposed. Further, when a thermophysical value at a high temperature of 1000 ° C. or higher is required, the sample may be altered or the measuring device may be deteriorated by heating the sample to a high temperature each time each thermophysical value is measured.

  In the 1970s, Cezairliyan et al. Of the United States developed a method for measuring the specific heat capacity and hemispherical total emissivity of a conductive material at a temperature of 1000 ° C. or higher with a single measuring device at high speed. The characteristic of this measurement method is the method of heating the sample. The electric charge stored in a large-capacity battery or capacitor is passed through the conductive sample, and the sample is heated to 3000 ° C. by Joule heat generated by the pulsed large current flowing in the sample. The above high temperature could be heated within 0.2 seconds.

  In this measurement method, the temperature and electrical resistance of the sample are measured during the above-described heating and cooling of the sample after energization, and the above 2 balance equation is calculated by the heat balance relational expression of the generated Joule heat, the heat capacity of the sample, and the heat radiation. Two thermophysical values were derived. Although this measurement method is limited to conductive materials, it has realized high-speed measurement of thermophysical values at high temperatures of 2000 ° C and above, which has been very difficult to measure, and is due to sample deterioration and measurement device degradation. It was an epoch-making method that minimizes errors and enables a significant reduction in measurement costs.

  However, this measurement method cannot measure the thermal conductivity and the thermal diffusivity necessary for the heat transfer analysis, and these thermophysical values need to be measured separately. Correspondingly, Righini et al. Of Italy developed a method to measure the thermal conductivity at the same time by measuring the temporal change of the temperature distribution of the sample during pulsed heating, but the thermal conductivity is not necessarily obvious. Since it is calculated, it has not spread widely.

  In principle, thermal conductivity is defined as the product of specific heat capacity, density and thermal diffusivity. In many cases, the temperature dependence of the density of solids is very small compared to the temperature dependence of thermal conductivity and specific heat capacity, so the thermal diffusivity at high temperatures is generally the value of density at room temperature and thermal diffusion at high temperatures. The thermal conductivity can be calculated from the measurement results of the rate and specific heat capacity. Currently, the thermal diffusivity of solids is generally measured by the flash method.

  However, when measuring the thermal diffusivity of a high-temperature substance by the flash method, the temperature of the sample is generally controlled using a resistance furnace, so the measurable temperature has an upper limit of about 2700 ° C. As described above There is a possibility that the measurement will be affected by the deterioration of the sample and the deterioration of the measuring device.

  In solving the above-mentioned problems and measuring the thermal diffusivity of a high-temperature substance, physical properties such as specific heat capacity, hemispherical total emissivity, thermal conductivity, thermal diffusivity can be measured at once, Japanese Patent Application Laid-Open Publication No. 2004-151820 discloses a multiple thermal property measurement method and an apparatus for carrying out the method that can measure the physical property value even at a high temperature that cannot be measured by the method.

  This technology has a system configuration as shown in FIG. 5, and a capacitor 32 in the figure stores electric charge used for sample heating, and is configured by a computer as a control device to the gate electrode of a current switch 33 formed of a field effect transistor. By applying a control voltage signal from the data recording and control device computer 42, a heating current is supplied to the flat sample 35 having a thickness of 1 mm or less, and the sample 35 is self-generated by the generated Joule heat. Let it heat.

  The voltage signal after the potential difference between both ends of the standard resistor 34 is amplified by the signal adjustment amplifier 40 is input to the data recording and control computer 42, and the magnitude of the heating current flowing through the sample 35 is measured. Further, a signal after the potential difference in the sample 35 is amplified by the signal adjustment amplifier 41 is input to the data recording and control device computer 42, and the magnitude of the voltage applied to the sample 35 is measured. The electric power required to heat the sample 5 is calculated from the product of the current and voltage, and the Joule heat per unit time generated in the sample is continuously measured.

  The temperature of the sample 35 heated as described above is measured by a radiation thermometer 37 using a silicon photodiode having a time resolution of about several tens of microseconds as a detection element, and the signal is transmitted to a computer for data recording and control. 42. The vertical spectral emissivity necessary for converting the luminance temperature measured by the radiation thermometer 37 into a true temperature is a DOAP that quickly determines a Stokes parameter representing the polarization state of light without having a mechanical drive. Continuous measurement using a monochromatic ellipsometer of the type.

  The data recording and control computer 42 monitors the temperature signal of the radiation thermometer 37 and controls the current flowing through the sample 35 by adjusting the gate voltage of the current switch 33 so that the sample 35 has a set temperature. I do. A field effect transistor is used as the current switch 33, and the gate voltage is feedback-controlled to keep the sample temperature constant at a predetermined target value.

  The sample heating current feedback control is continued for a certain period of time, then the feedback control is stopped, and the subsequent gate voltage value is held at the control value immediately before the feedback control is stopped. The sample surface of the sample 35 to be measured by the radiation thermometer 37 is irradiated with a laser beam from the pulse YAG laser 36 by a trigger signal output from the data recording and device control computer 42 to heat the sample. The surface temperature change of the sample 35 after irradiation with the laser beam for light heating is measured by the radiation thermometer 37, and the temperature change is fitted to the one-dimensional heat diffusion model by the data recording and control device computer 42 to thereby diffuse the heat. Calculate the rate. In this apparatus, since the radiation temperature of the sample is measured at a sampling interval of several tens of microseconds, a silicon photodiode having a high response speed as described above is used as the light intensity detection element of the radiation thermometer. In order to reduce heat loss due to heat exchange between the sample and gas, the measurement atmosphere is set to a vacuum of 1 mPa or less.

On the other hand, the surface of the sample 35 is irradiated with light from the light source 38 of the high-speed ellipsometer, the reflected light is detected by the detector 39 of the high-speed ellipsometer, and the signal is input to the computer 42 for data recording and control device. The spectral emissivity is measured.
JP 2005-249427 A A. Cezairliyan, JLMcClure, CWBeckett: J. Res. National Bureau of Standards, Vol. 75C-1 (1971), pp. 7-18

  In the thermophysical property measurement method proposed by the present inventors as described above, for example, the sample is heated as shown in FIG. 6, and the temperature change of the sample due to pulse laser irradiation is measured. That is, in the example shown in FIG. 6, in step 1 where 0 <t <480 ms, the sample in the room temperature is subjected to energization heating while feedback-controlling the gate voltage of the field effect transistor, and held at the target temperature. Next, in step 2 where t = 480 ms, the feedback control performed in step 1 is stopped. Next, in Step 3 where 480 <t <800 ms, the gate voltage value finally derived by the feedback control is maintained. Next, in step 4 at t = 480.55 ms, the sample is irradiated with a pulse laser, and the temperature change of the sample due to the pulse laser is measured. Finally, in step 5 where t> 800 ms, the gate voltage is set to zero and the sample temperature is quickly returned to room temperature.

  In some cases, the desired heating is actually performed and accurate measurement can be performed by the conventional method as described above. However, the sample temperature change similar to that in FIG. It was found that the sample temperature could not be kept constant with good performance. FIG. 7 shows an example of failure of sample heating by such a conventional method. FIG. 7A and FIG. 7B show the results of two heating experiments performed continuously on the same tantalum sample under the same heating conditions. In these experiments, in both cases, the target temperature was set to 2100 K, and the time for continuing the feedback control was set to 300 ms. In the experiment of FIG. 7A, the temperature is not kept constant in step 3, that is, the step of maintaining the gate voltage value finally derived by the feedback control, and the temperature gradually increases. In contrast, in the example of FIG. 7B, in step 3, the temperature gradually decreases.

  As a result of examining the cause of the failure of the sample heating as described above in various experiments, step 1 is performed in which current heating is performed on the sample in the room temperature state while feedback controlling the gate voltage of the field effect transistor, and the target temperature is maintained. It was found that this was caused by a large variation in the gate voltage control value at. Focusing on FIG. 8 (b) showing the time change of the gate voltage control value of the field effect transistor in the heating experiment shown in FIG. 8 (a) corresponding to FIG. 7 (b), the rapid change from the start of heating to the time of 100 ms. It can be seen that there is a large difference in the gate voltage control value during heating and after reaching the vicinity of the target temperature thereafter.

  In the example shown in the figure, the gate voltage Vg is about 2.V from the saturated drain voltage value of the gate voltage of the field effect transistor used this time at the time when the temperature is kept constant from the rapid heating state of the sample temperature. This shows that the voltage drops rapidly to 7 V, and it is understood that the fluctuation range of Vg needs to be considerably smaller than the saturation drain voltage value at the stage where the temperature is kept constant. However, in the conventional method, since the feedback control is already executed in the stage where the rapid heating is performed, the fluctuation range of the feedback control value of Vg set in advance is a wide range with the saturation drain voltage value as the upper limit. There is a need. Further, in order to execute rapid heating, it is necessary to increase the value of the proportional variable (P value) of the PID control theory adopted in the feedback control algorithm. For this reason, in the above prior art, it is necessary to make the fluctuation range and P value of Vg large, and inevitably Vg, that is, Joule heat generated per unit time when the temperature is constant after rapid heating. The amount will vary greatly. In the above prior art, when the value of Vg is maintained at the final control value after the feedback control is stopped, the Joule heat generation corresponding to the final control value coincides with the amount of heat loss due to radiation or heat transfer from the sample at the target temperature. Thus, it is utilized that the temperature constant state is continued for a short time even after the feedback control is stopped. However, when the variation in Vg during feedback control is large, the final control value often becomes a value that does not correspond to the target temperature of the sample. When such inadequate heating is performed, the result of the thermophysical property measurement that first needs to hold the sample in a steady state becomes inaccurate.

  Therefore, the present invention performs energization heating while performing feedback control of the gate voltage of a transistor such as a field effect transistor so that the temperature of the object to be heated such as a sample becomes a target value, and the temperature of the object to be heated is sufficiently high. In the heating control that continues the constant temperature state only by holding the gate voltage after that, the constant temperature state is maintained with good reproducibility when holding the gate voltage after stopping the feedback control. It is a main object of the present invention to provide a heating method and a heating apparatus for an object that can be continued.

In order to solve the above-described problem, the object heating method according to the present invention controls the gate voltage of a transistor used to control the amount of current supplied to the conductive object to be heated, so that the temperature of the object to be heated reaches a predetermined target value. reach performs rapid heating by fixing the gate voltage to a predetermined voltage, after reaching the target value, starts the feedback control of the gate voltage such that the temperature of the heated object is held at the target value and continues the feedback control to converge to a temperature amplitude range in which the temperature of the heated object can be regarded substantially to have been kept constant at the target value, it stops the feedback control at the time which is kept constant at the target value, then The gate voltage value is held at the average value of the gate voltage control values at arbitrary multiple time points immediately before the feedback control is stopped, so that the temperature of the object to be heated is measured. Characterized by a constant hold the value.

  Another object heating method according to the present invention is characterized in that, in the object heating method, the control range of the gate voltage is limited to a predetermined range in a period during which the gate voltage is feedback controlled.

  According to another object heating method of the present invention, in the object heating method, the object to be heated is a conductive sample for measuring thermophysical properties, and the sample is optically heated immediately after holding the gate voltage, The thermophysical property is measured by measuring the subsequent temperature change.

The object heating device according to the present invention includes an energization heating means for energizing and heating a conductive object to be heated, a transistor disposed in an energization circuit for the object to be heated, and a temperature for measuring the temperature of the object to be heated. Measuring means; and a temperature control means for inputting a signal of the temperature measured by the temperature measuring means and controlling the gate voltage of the transistor so that the temperature of the object to be heated becomes a predetermined target value. in the control unit, initially rapidly heated to fix the gate voltage to a predetermined voltage, once, after reaching the target value, feedback the gate voltage such that the temperature of the sample is kept constant to the target value controlling to stop the feedback control after the temperature is held at the target value by feedback control, then, a plurality of immediately before stopping the feedback control of the value of the gate voltage By setting the average value of the gate voltage control value at the point, characterized by a constant holding the sample temperature to the target value even after stopping the feedback control.

  Another object heating device according to the present invention is characterized in that, in the object heating device, the control range of the gate voltage is limited to a predetermined range during a period in which the gate voltage is feedback-controlled.

  According to another object heating apparatus of the present invention, in the object heating apparatus, the object to be heated is a conductive sample for measuring thermophysical properties, and the sample is optically heated immediately after the holding of the gate voltage. The thermophysical property is measured by measuring the subsequent temperature change.

   Another object heating apparatus according to the present invention is characterized in that the object heating apparatus is used as a high-speed precision temperature heater for heating various objects.

  Another object heating apparatus according to the present invention is characterized in that the object heating apparatus is used as a heat treatment method for a metal or alloy using direct current heating.

  Since the present invention is configured as described above, current heating is performed while feedback controlling the gate voltage of a transistor such as a field effect transistor so that a heated object such as a sample reaches a target temperature, and then the gate voltage is held. In the heating control in which the constant temperature state is maintained simply by doing this, the constant temperature state can be continued with good reproducibility after the feedback control is stopped.

  In order to solve the above problems, the present invention controls the gate voltage of a transistor used to control the amount of current supplied to the conductive object to be heated, and rapidly heats the object to be heated until the temperature reaches the target value. After reaching the value, the feedback control is continued until the temperature of the object to be heated converges to a temperature amplitude range that can be substantially assumed to be held at the target value, and when the target temperature is held constant, the feedback control is stopped. Thereafter, the temperature of the object to be heated is kept constant at the target value by holding the gate voltage value at the average value of the gate voltage control values at a plurality of time points immediately before stopping the feedback control.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a change in the temperature of the sample when the heating method of the present invention is actually used, and corresponds to the change in the sample temperature during the experiment by the conventional heating method shown in FIG. ing. The heating system for executing the heating method according to the present invention uses the same heating system as that of the previous application by the present inventors shown in FIG. 5, and a photoconductive hybrid pulse heating system 1 as shown in FIG. Is used.

  The capacitor 2 in FIG. 2 stores electric charge used for heating the sample, and applies a control voltage signal to the gate electrode of the field effect transistor 3 from a temperature control / signal recording computer 12 configured by a computer as a control device. A heating current is supplied to the sample 5 and the sample 5 is self-heated by the generated Joule heat.

  A signal of potential difference between both ends of the standard resistor 4 is input to the temperature control / signal recording computer 12 and the magnitude of the heating current flowing through the sample 5 is measured. Further, a potential difference signal in the sample 5 is input to the temperature control / signal recording computer 12 to measure the magnitude of the voltage applied to the sample 5. The electric power required to heat the sample 5 is calculated from the product of the current and voltage, and the Joule heat per unit time generated in the sample is continuously measured.

  The temperature of the sample 5 heated as described above is measured by a radiation thermometer 7 using a silicon photodiode having a time resolution of about several tens of microseconds as a detection element, and the signal is transmitted to a temperature control / signal recording computer. 12 is input. The vertical spectral emissivity necessary for converting the luminance temperature measured by the radiation thermometer 7 to a true temperature is a DOAP that quickly determines a Stokes parameter representing the polarization state of light without having a mechanical drive. Continuous measurement using a monochromatic ellipsometer of the type.

  The temperature control / signal recording computer 12 monitors the temperature signal of the radiation thermometer 7 and adjusts the gate voltage of the field effect transistor 3 so that the temperature of the sample 5 is set, thereby setting the sample temperature to the target value. Hold constant.

  After the sample temperature is kept constant at the target value by the feedback control of the gate voltage, the feedback control is stopped, and the gate voltage value is held at the average value of the gate voltage control values at any multiple time points immediately before the feedback control is stopped. During a constant temperature state that is maintained for a short time, a light pulse is emitted from the pulse laser 6 to the back surface of the surface of the sample 5 measured by the radiation thermometer 7 by a signal from the temperature control / signal recording computer 12. In this way, instantaneous light heating is performed. At that time, a part of the pulsed light flux is taken into the photodetector 13 by the beam splitter 10, and the signal from the detector is analyzed by the temperature control / signal recording computer to determine the irradiation time of the light pulse.

  The surface temperature change of the sample 5 after the light pulse irradiation is measured by the radiation thermometer 7, and the temperature change and the computer 12 for recording the temperature are fitted to the one-dimensional heat diffusion model by calculating the thermal diffusivity. . In this apparatus, since the radiation temperature of the sample is measured at a sampling interval of several tens of microseconds, a silicon photodiode having a high response speed as described above is used as the light intensity detection element of the radiation thermometer. In order to reduce heat loss due to heat exchange between the sample and gas, the measurement atmosphere is set to a vacuum of 1 mPa or less.

  On the other hand, the surface of the sample 5 is irradiated with light from the semiconductor laser 8 which is the light source of the high-speed ellipsometer, the reflected light is detected by the high-speed ellipsometer 9, and the signal is input to the temperature control / signal recording computer 12. The spectral emissivity of the sample surface is measured. The subsequent measurement of thermophysical properties has been described in detail in the above-mentioned previous application, and since there is little direct relationship with the present invention, explanation here is omitted.

  Using the apparatus as described above, in the present invention, the sample is heated as shown in FIG. In the heating experiment shown in FIG. 1, in the first step 1, rapid heating is performed in step 1 corresponding to the time region until reaching the preset target temperature 2100K. When the target temperature is reached by rapid heating, feedback control of the gate voltage is started so as to keep the target temperature constant. This feedback control period corresponds to the time region of step 2 in FIG. 1, and unlike the prior art, the sample temperature has already reached the target value before starting the feedback control. It is not necessary for the fluctuation range of the control value to include a large value as required during rapid heating. Therefore, an appropriate fluctuation range of the gate voltage control value is set in advance to keep the target temperature constant. In the experiment shown here, the control value fluctuation range of the gate voltage was limited to 2.8 to 2.9 V, and the fluctuation of the sample temperature and the control gate voltage value in the time region of Step 2 could be reduced.

  After the end of step 3, the feedback control is stopped. The average value of the 20 gate voltage control values derived immediately before the feedback control is stopped is calculated by the temperature control / signal recording computer 12, In the time region where Step 6 ends from the start of Step 4 after the feedback control is stopped, the value of the gate voltage is held at this average value. In this experiment, the time interval for deriving the 20 gate voltage control values used for calculating the average value is 2 ms. This time region corresponds to step 3 and corresponds to a period of 2 ms immediately before the end of step 2. ing.

  After the feedback control is completed, an average value of gate voltage control values at a plurality of time points immediately before stopping the feedback control is obtained, and the gate voltage is held at that value from the start time of step 4 to the end of step 6. The time domain from the start of the hold of the gate voltage to the time of pulse laser irradiation shown as step 5 in the figure corresponds to step 4, which is 20 ms in this experiment. In this experiment, pulse laser irradiation is not performed in order to confirm the continuity of the sample temperature after feedback control. In the time domain after laser irradiation shown in step 6, the temperature change of the sample is measured by a pulse laser to obtain various physical property values as detailed in the previous application. The period of step 6 is a period for acquiring data necessary for calculating the thermal diffusivity. Finally, the gate voltage is set to zero after the preset measurement operation end time, and the sample temperature is quickly returned to room temperature.

  As a result of the above control, the temperature can be kept constant at the time of holding the gate voltage with good reproducibility. In addition, the temperature can be kept constant when holding the gate voltage with a shorter feedback control time than in the past. Furthermore, the temperature fluctuation at the time of feedback control can be reduced, and the magnitude of the overshoot of the sample temperature generated at the end of the rapid heating is reduced. These effects enable efficient and accurate thermophysical property measurement.

  In order to confirm the effect of the present invention, a comparison between the conventional patent technique continuously performed using the same tantalum sample and the heating experiment performed by the technique of the present invention is shown in FIGS. FIG. 3A shows an example of the fluctuation range of the gate voltage by the same conventional heating method as in FIG. 8B, and the fluctuation range is large as Vg = 2.7 to 6 V as described above. It is shown. On the other hand, according to the heating method of the present invention shown in FIG. 3B, the gate voltage Vg is maintained at 2.8 to 2.9 V, and the allowable range of the control value of the gate voltage is narrow. It is shown. By performing such control, the temperature can be kept constant with high reproducibility when holding the gate voltage after feedback control, and the temperature is kept at a predetermined constant value when holding the gate voltage with a shorter feedback control time than conventional. Can do. Thereby, the experiment time is shortened, the contamination time of the sample is reduced, accurate measurement is possible, and the measurement cost can be reduced.

  4 (a) and 4 (b) show the temperature change of the sample obtained during the heating shown in FIGS. 3 (a) and 3 (b), respectively, and the brightness of the sample by the conventional heating method is shown. FIG. 4A showing the temperature change shows that there is a state where the temperature does not become constant in Step 3 after Step 2 in which feedback is stopped as described above. In contrast, in the heating method of the present invention shown in FIGS. 3B and 4B, the gate voltage during the feedback control in step 2 is stable as described above when the gate voltage is held after the feedback is stopped. In addition, since the average value of several tens of points immediately before the feedback control is stopped is used as the hold value, it can be maintained extremely stably at the same temperature as the predetermined temperature of the feedback control even after the feedback control. This has the effect of improving the accuracy of thermal diffusivity and hemispherical total emissivity measurements.

The heating method of the present invention as described above is mainly used to energize a sample for measuring thermophysical values such as specific heat capacity, hemispherical total emissivity, thermal conductivity, thermal diffusivity of various substances at high temperatures as described above. Although it can be suitably used for heating, this heating method is used as a high-speed precision temperature heater that instantaneously requires a predetermined amount of heat in, for example, an energizing heater of a test apparatus or various devices. Can also be used.
Further, for example, in the heat treatment of a metal or alloy, it is possible to reach the target temperature accurately and at high speed and hold the temperature for an accurate time.

It is experimental data which shows the change of luminance temperature when a sample is heated with the heating method of this invention. It is a figure which shows the example of the photoconductive hybrid pulse heating system to which the heating method of this invention is applied. It is experimental data which shows the fluctuation | variation state of the gate voltage by the heating method of this invention and a prior art example especially during feedback control. It is an experimental data which shows the state of the luminance temperature change of the sample by the heating method of this invention and a prior art example. It is a system diagram of the conventional thermophysical property measuring apparatus which the present inventors previously proposed. It is experimental data which shows the state of a brightness temperature change when a sample is heated with the conventional apparatus. It is an experimental data which shows the example of failure when a sample is heated with the conventional apparatus. It is experimental data which shows the cause of the conventional sample heating failure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric hybrid pulse heating system 2 Capacitor 3 Field effect transistor 4 Standard resistance 5 Sample 6 Pulse laser 7 Radiation thermometer 8 Semiconductor laser 9 High-speed ellipsometer 10 Beam splitter 11 Voltage measuring probe 12 Temperature control / signal recording computer 13 Photodetector

Claims (8)

Control the gate voltage of the transistor used to control the amount of electricity applied to the conductive object to be heated, and fast heating by fixing the gate voltage to a predetermined voltage until the temperature of the object to be heated reaches a predetermined target value. And
After reaching the target value, and starts the feedback control of the gate voltage such that the temperature of the heated object is held at the target value,
Continued feedback control until the temperature of the heated object to converge to a temperature amplitude range regarded substantially to have been kept constant at the target value,
The feedback control is stopped when the target value is held constant, and then the object to be heated is held by holding the gate voltage value at the average value of the gate voltage control values at any plurality of time points immediately before stopping the feedback control. A method for heating an object, characterized in that the temperature of the object is kept constant at a target value.   The object heating method according to claim 1, wherein a control range of the gate voltage is limited to a predetermined range in a period during which the gate voltage is feedback-controlled. The heated object is a conductive sample for measuring thermal properties,
Immediately after holding the gate voltage, the sample is photoheated,
The thermophysical property measuring method using the object heating method according to claim 1, wherein a thermophysical property is measured by measuring a subsequent temperature change of the sample. Energization heating means for energizing and heating the conductive object to be heated;
A transistor disposed in the energization circuit of the heated object;
Temperature measuring means for measuring the temperature of the heated object;
A temperature control unit that inputs a temperature signal measured by the temperature measurement unit and controls the gate voltage of the transistor so that the temperature of the object to be heated becomes a predetermined target value;
In the temperature control means, first heated rapidly by fixing the gate voltage to a predetermined voltage, once, after reaching the target value, the gate voltage such that the temperature of the sample is kept constant to the target value the feedback control, stopping the feedback control after the temperature is held at the target value by feedback control, then, the average value of the gate voltage control value at a plurality time point immediately before stopping the feedback control of the value of the gate voltage An object heating apparatus characterized in that, by setting, the sample temperature is kept constant at a target value even after feedback control is stopped.   5. The object heating apparatus according to claim 4, wherein the gate voltage is limited to a predetermined range in a period during which the gate voltage is feedback controlled. The heated object is a conductive sample for measuring thermal properties,
Immediately after holding the gate voltage, the sample is photoheated,
The thermophysical property measuring apparatus using the object heating device according to claim 4, wherein the thermophysical property is measured by measuring a subsequent temperature change of the sample. An object heating apparatus using the object heating apparatus according to claim 4 as a high-speed precision temperature heater for heating various objects. 5. An object heating apparatus using the object heating apparatus according to claim 4 as a heat treatment method for a metal or alloy using direct current heating.

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