JP2949314B2 - Calorimeter and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calorimeter and a calorimeter suitable for measuring a calorific value of a small amount of sample.

[0002]

2. Description of the Related Art Conventionally, an adiabatic calorimeter has been used as a means for measuring the heat capacity of a substance with high accuracy. An adiabatic calorimeter is mainly composed of a sample container and an adiabatic shield on its outer periphery. The sample container is equipped with a heater for heating the sample and a thermometer for measuring the temperature of the sample, and the adiabatic shield is equipped with a heater for controlling the temperature. The temperature difference between the sample container and the adiabatic shield is detected in order to control the same temperature. Thermocouples are connected in series.

In order to measure the heat capacity, first, a certain amount of heat energy is applied to the sample and the sample container by a heater, the amount of temperature rise at that time is measured, and the heat capacity is obtained by equation (1).

[0004]

[Formula 1] C = ΔE / ΔT ……………………………………………… (1) C: Heat capacity ΔE: Thermal energy ΔT: Temperature rise Conventional thermal insulation In the type calorimeter, a calorimetric circuit for measuring ΔE and ΔT and an adiabatic control circuit for making the adiabatic shield the same as the temperature of the sample container operate independently. First, ΔE
Is measured by a formula (2) in which a current is passed through a heater wound around a sample container for a certain time interval, and ΔT is a resistance value of a resistance thermometer or the like measured with a precision of mK using a bridge or the like. .

[0005]

ΔE = I ² · R · Δt ··················· (2) ΔE: thermal energy I: current R: resistance of heater Δt: time Interval This is the calorimetric circuit. On the other hand, the electromotive force of the thermocouple attached between the sample container and the heat shield was measured with a voltmeter,
The output is input to a PID controller, the output from the PID controller is amplified by an amplifier, and the current flowing through a heater wound on the heat shield is adjusted so that the temperature of the heat shield becomes the same as that of the sample container. doing. This is the adiabatic control circuit. Therefore, since the heat capacity is measured by such a method, in order to measure the heat capacity with high accuracy, it is necessary to make the temperature of the heat insulating shield and the temperature of the sample container the same, and to prevent heat conduction from the sample container.

In recent years, electronic components have been miniaturized due to advances in microelectronics. It is required to measure the thermophysical properties of the material of the minute electronic component, for example, the thin film material with high accuracy. A conventional calorimeter cannot measure the heat capacity of a small amount of sample with high accuracy and is at least 10 to 20 g.
In order to measure the heat capacity of a sample or a thin film material that requires only a small amount of a sample and that is available in a very small amount, the development of an adiabatic calorimeter for a small amount of sample is desired. However, there are two problems when measuring a small amount of sample. One is that the value of the heat capacity of the sample itself is small because it is very small, so that the relative value of the heat capacity of the sample becomes smaller than the entire heat capacity including the sample container, and the detection sensitivity is lowered. The other is that there is a limit in the temperature control ability between the sample container and the heat insulating shield, so that heat conduction through the lead wire between the two occurs, and the temperature rise (ΔT)
, And the smaller the sample, the greater the effect.

One method for solving these problems is to reduce the heat capacity of the sample container. In particular, there is a method of removing the thermometer from the sample container. However, doing so requires another means for detecting the temperature of the sample container.

[0008] About that, Journal of Physics e Scientific Instruments, 1
7 (1984) 1054 (J. Phys. E: Sci. Instru
m., 17 (1984) 1054).

[0009]

In the apparatus described in the above document, a temperature measuring block for attaching a thermometer detached from the sample container is located inside the heat insulating shield. By making the temperature of the sample container and the temperature measurement block the same, the sample temperature can be measured with a thermometer attached to the temperature measurement block. At this time, in order to make the temperature of both the same, a thermocouple must be attached between the two, and the temperature of the temperature measurement block must be controlled so that the thermoelectromotive force becomes zero. Thus, it is possible to remove the thermometer from the sample container. However, in the above-described conventional apparatus, a thermocouple must be newly attached to the sample container, and heat conduction from the sample container is generated by the thermocouple. As a result, there is a problem that an error occurs in the amount of temperature rise of the sample.

In addition, since the temperature control system and the temperature measurement system of the temperature measurement block operate completely independently, no signal is transmitted and received between the two, and the temperature and the temperature change of the temperature measurement block are not necessarily changed. There is a problem that the temperature and temperature change of the sample are not accurately represented. For example, when the temperature of the temperature measurement block rises, the temperature change indicates the temperature increase of the sample, or the temperature measurement block is heated by an external factor such as heat conduction from the heat insulating shield just outside the temperature measurement block. It is impossible to determine whether only the temperature is rising.

An object of the present invention is to provide a calorimeter and a calorimeter capable of measuring the heat capacity of a trace sample with high accuracy.

[0012]

An object of the present invention is to provide a sample container holding a small amount of sample, a first heating element for heating the sample container, an insulating container supporting and containing the sample container, and an insulating container. A second heat generating element for heating the heat-insulating container, a heat-insulating container temperature sensor for detecting the temperature of the heat-insulating container, or a metal resistance wire provided on the heat-insulating container wall for detecting the temperature as a change in resistance value; And a thermocouple that is in contact with the heat insulating container and detects a temperature difference.

The object is to provide a sample container holding a small amount of sample, a first heating element for heating the sample container, a heat insulating container for supporting and containing the sample container, and a second heat source for heating the heat insulating container. A heating element, an insulated container temperature sensor for detecting the temperature of the insulated container or a metal resistance wire provided on the wall of the insulated container and detecting the temperature as a change in resistance value, and a contact portion in contact with the sample container and the insulated container A thermocouple for detecting a temperature difference, an adiabatic control circuit for inputting the temperature difference detected by the thermocouple and controlling energy supplied to the second heating element so as to eliminate the temperature difference; The amount of energy supplied to the heating element is measured, and the temperature of the heat insulating container detected by the temperature sensor of the heat insulating container and the temperature difference detected by the thermocouple are input, and the temperature of the heat insulating container is reduced when the temperature difference becomes substantially zero. As the temperature of the trace sample, It is achieved by having a calorimetric circuit for calculating the heat capacity with Nerugi amount.

The object is to provide a sample container holding a sample and having a heating element, an insulating container including the sample container and having a heating element, an insulating container temperature sensor for detecting the temperature of the insulating container, Using a calorimeter equipped with a temperature difference sensor for detecting the temperature difference between the sample container and the heat-insulating container, controlling the heating element of the heat-insulating container so that the temperature difference becomes substantially zero, and controlling the heat-insulating container temperature at that time. This is achieved by defining the sample temperature.

[0015]

According to the above construction, an insulated container temperature sensor for detecting the temperature in the insulated container or a metal resistance wire provided on the insulated container wall for detecting the temperature as a change in resistance is provided for the sample container and the insulated container. If only the temperature at which the temperature difference between the sample container and the heat insulating container detected by the thermocouple contacting the contacts is substantially zero is adopted as the temperature of the sample, the temperature of the sample is detected by detecting the temperature of the heat insulating container. Knowing that, the temperature sensor can be excluded from the sample container, and it is possible to reduce the number of parts attached to the sample container, reduce the heat capacity of the sample container, and measure the calorific value of a small amount of sample, as well as to reduce the size of the sample container. .

Further, by eliminating the temperature sensor from the sample container, heat conduction by the conductor of the temperature sensor is eliminated, and the error in the amount of temperature rise of the sample due to the heat conduction from the sample container is reduced, so that the accuracy of the calorimetric measurement is improved. I do.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 First, the structure of the apparatus will be described.

FIG. 1 is a sectional view of a sample container and a heat insulating container of the heat insulating calorimeter of the present embodiment.

The sample container 1 comprises a sample container lid 2, a sample container main body 3, a sample container heater 5, and a heater protection cover 4. The contacts of the thermocouple 6 are attached to the sample container 1 and the heat insulating container 7. A temperature sensor 8 is provided on the inner wall of the heat insulating container 7.
A heat insulating container heater 9 for controlling the temperature is uniformly wound on the outer wall of the heat insulating container 7.

Next, the operation will be described.

FIG. 2 is a block diagram of the adiabatic control circuit and the calorimetric measuring circuit.

The adiabatic control is performed as follows. Thermocouple 6
The temperature difference between the sample container 1 and the heat insulating container 7 is detected as a temperature difference signal by the temperature difference detector 10, the temperature difference signal is output to the PID controller 11, and the output signal from the PID controller is output by the amplifier 12. It is amplified and output as a current to the insulated container heater 9, and the temperature of the insulated container 7 is
Control the same as. For example, when the temperature of the heat insulating container 7 is lower than that of the sample container 1, the polarity of the thermocouple 6 is arranged so that the thermoelectromotive force of the thermocouple 6 becomes negative. Is configured to be increased. what if,
When the temperature of the heat insulating container 7 is lower than that of the sample container 1, the thermoelectromotive force becomes negative. However, by increasing the current to the heat insulating container heater 9, the temperature of the heat insulating container 7 rises and approaches the temperature of the sample container 1, The value of the thermoelectromotive force also approaches zero. Then, the current of the heat insulating container heater 9 is finely adjusted so that the temperatures of the two become equal. In this manner, the temperature difference between the sample container 1 and the heat insulating container 7 is eliminated, the sample container 1 is insulated from the outside, and the temperature of the sample container 1 is controlled very stably.

On the other hand, a current is intermittently applied to the sample container heater 5 wound around the sample container 1 for a certain time interval, and the voltage applied to both ends of the sample container heater 5 and the current flowing through the sample container heater 5 at that time are referred to as voltage and current. The heat energy applied to the sample container 1 is measured by the total 15.

[0025]

ΔE = I · V · Δt (3) ΔE: thermal energy I: applied current V: applied voltage Δt: time interval Then, the heat energy data is sent to the microcomputer 14. The signal of the temperature sensor 8 is measured by a voltmeter or a resistance measuring device 13 and sent to the microcomputer 14 as data of the sample temperature. At this time, the temperature difference from the thermocouple 6 is sent from the temperature difference detector 10 to the microcomputer 14 as a temperature difference signal, and only the temperature when the temperature difference is within several mK, preferably zero, is adopted as the sample temperature. The amount of temperature rise before and after the application of thermal energy is measured as described above. First, under a condition in which adiabatic control is performed, a set value (for example, 10 m
(K / h) or less, the time change of the sample temperature is extrapolated to the middle of the time from the start to the end of sample heating, and the temperature at that time is determined as the temperature before sample heating. Next, after heating is completed, it is confirmed that the time change of the sample temperature has fallen below a certain set value, and the temperature change is extrapolated to the middle of the time from the start to the end of the immediately preceding sample heating, and the temperature at that time is sampled. Calculate as the temperature after heating. In this way, the amount of temperature rise before and after heating can be obtained.

[0026]

ΔT = Tf−Ti (4) ΔT: Temperature rise Tf: Temperature after sample heating Ti: Before sample heating Temperature Based on these results, the heat capacity of the sample can be determined by equation (1). In order to measure the heat capacity with high accuracy, conditions are set so that ΔT = 1 to 2K, and the measurement is performed while intermittently repeating a mode for heating the sample and a mode for measuring the temperature in a thermal equilibrium state. Further, as the temperature sensor 8, a platinum resistance thermometer having an accuracy of several mK is used.

By forming the sample container 1 and the heat insulating container 7 as shown in FIG. 1, and forming the heat insulating control circuit and the calorific value measuring circuit as shown in FIG. 2, the lead wire from the sample container 1 is connected to the thermocouple 6 and the sample. Since only the container heater 5 is used, heat conduction can be reduced. Further, it is confirmed that the temperature of the heat insulating container 7 is the same as that of the sample container 1 using the thermocouple 6, and the measured value of the temperature sensor 8 at that time is adopted as the sample temperature.
The sample temperature can be measured with high reproducibility and accuracy.

Embodiment 2 The structure is basically the same as that of Embodiment 1, except that a metal resistance wire 16 is wound around the entire heat insulating container 7 in place of the temperature sensor 8, and the change in the resistance value of the metal resistance wire 16 due to the temperature is measured. Detected as a temperature change. In this manner, since the metal resistance wire 16 detects the temperature of the entire heat insulating container 7, an average value is obtained even if there is a temperature distribution, and the temperature of the heat insulating container 7 having a small standard deviation can be measured.

As described above, by measuring the temperature of the insulated container instead of the sample container, the thermometer is excluded from the sample container, whereby the heat capacity of the sample container is reduced, and the sample that required 10 g in the past was required. Was reduced to 50 mg, and it was possible to measure with the same accuracy. Further, the lead wire of the thermometer coming out of the sample container is eliminated, so that heat conduction can be reduced.

Also, by employing only the temperature measured when the temperature of the heat insulating container becomes equal to the temperature of the sample container by the thermocouple as the sample temperature, abnormal temperature change of the heat insulating container due to heat conduction from the outside can be prevented. In addition, erroneous measurement such as measurement as a change in sample temperature can be prevented.

[0031]

According to the present invention, a temperature sensor or a metal resistance wire is provided in a heat insulating container, and when the temperature difference between the sample container and the heat insulating container becomes substantially zero, the temperature of the heat insulating container is determined as the temperature of the sample. In addition, the temperature sensor can be excluded from the sample container to reduce the heat capacity of the sample container, and the calorie measurement of a small amount of sample can be obtained.

In addition, by eliminating the temperature sensor from the sample container, heat conduction by the conducting wire of the temperature sensor is eliminated, and the error in the amount of temperature rise of the sample due to heat conduction from the sample container is reduced, so that the accuracy of the calorimetric measurement is improved. I do.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sample container and a heat insulating container of an adiabatic calorimeter according to an embodiment of the present invention.

FIG. 2 is a block diagram of an adiabatic control circuit and a calorimetric measurement circuit according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sample container 2 Sample container lid 3 Sample container main body 4 Heater protection cover 5 Sample container heater 6 Thermocouple 7 Insulated container 8 Temperature sensor 9 Insulated container heater 10 Temperature difference detector 11 PID controller 12 Amplifier 13 Voltmeter or resistance measuring device 14 Microcomputer 15 Voltage and ammeter 16 Metal resistance wire

Claims (5)

(57) [Claims] 1. A sample container holding a small amount of sample, a first heating element for heating the sample container, a heat insulating container supporting and containing the sample container, and a second heating element for heating the heat insulating container. And a thermocouple for detecting a temperature difference between the sample container and the heat-insulating container by bringing a contact portion into contact with the sample container and the heat-insulating container. 2. A sample container holding a small amount of sample, a first heating element for heating the sample container, a heat insulating container supporting and containing the sample container, and a second heating element for heating the heat insulating container. And a metal resistance wire provided on the heat insulating container wall and detecting a temperature as a change in resistance value, and a thermocouple for detecting a temperature difference by bringing a contact portion into contact with the sample container and the heat insulating container. Calorimeter. 3. A sample container holding a small amount of sample, a first heating element for heating the sample container, a heat insulating container supporting and containing the sample container, and a second heating element for heating the heat insulating container. And a heat insulating container temperature sensor for detecting the temperature of the heat insulating container, a thermocouple for detecting a temperature difference by bringing a contact portion into contact with the sample container and the heat insulating container, and inputting the temperature difference detected by the thermocouple. An adiabatic control circuit for controlling the energy supplied to the second heating element so as to eliminate the temperature difference, and an adiabatic vessel temperature detected by the adiabatic vessel temperature sensor by measuring the amount of energy supplied to the first heating element And a calorie measurement circuit for calculating a heat capacity using the energy amount as the temperature of the adiabatic container when the temperature difference is substantially zero, and when the temperature difference becomes substantially zero. Calorimetry characterized by Setting device. 4. A sample container holding a small amount of sample, a first heating element for heating the sample container, a heat insulating container supporting and containing the sample container, and a second heating element for heating the heat insulating container. And a metal resistance wire provided on the heat insulating container wall and detecting a temperature as a change in resistance, a thermocouple for detecting a temperature difference by bringing a contact portion into contact with the sample container and the heat insulating container, and detecting the thermocouple. An adiabatic control circuit for inputting a temperature difference and controlling energy supplied to the second heating element so as to eliminate the temperature difference; and an adiabatic container temperature sensor for measuring an amount of energy supplied to the first heating element. Inputting the temperature of the insulated container detected by the thermocouple and the temperature difference detected by the thermocouple, and when the temperature difference becomes substantially zero, the heat capacity is calculated by using the amount of energy as the temperature of the insulated container as the temperature of the trace sample. That it has a calorimeter Characteristic calorimeter. 5. A sample container holding a sample and having a heating element, an insulating container including the sample container and having a heating element, an insulating container temperature sensor for detecting a temperature of the insulating container, and the sample container And a calorimeter equipped with a temperature difference sensor for detecting a temperature difference between the heat insulating container and a heating element of the heat insulating container so that the temperature difference becomes substantially zero. And a calorimetric method.