JPH05281050A - Thermal analysis device - Google Patents

Abstract

PURPOSE:To accurately measure the temperature of a sample or a heater by improving the cold junction compensating method for a thermocouple which is used as a temperature sensor in thermal analysis devices. CONSTITUTION:In a thermal analysis device, a thermocouple made of the same material as the material of a thermocouple arranged in the neighborhood of a sample 8 is arranged in a place where temperature is stably controlled, and output of the thermocouple is corrected based on signals from a temperature sensing element 3 stuck on the former thermocouple. Thus, a cold junction compensation device is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an improvement of a thermal analyzer for examining the temperature dependence of physical properties of a material by measuring the temperature and the physical properties of the material at the same time, particularly for the purpose of improving the accuracy of temperature measurement. It is about.

[0002]

2. Description of the Related Art Conventionally, the following two types of cold junction compensation have been used for this type of invention. As shown in FIG. 2, a thermocouple was formed with two kinds of metals, the first junction was placed near the sample, the second junction was immersed in ice water, and the voltage between the same metal wires was measured. To measure the sample temperature.

As shown in FIG. 3, a thermocouple is formed by joining two kinds of metals, and a sample is placed near the joining point.
A sample temperature is measured by arranging a thermosensitive element in the vicinity of a junction with a copper electrode for measuring the voltage between metal wires and correcting the voltage between both metal wires based on the signal of the thermosensitive element.

[0004]

The above-mentioned prior arts all have the function of compensating the cold junction of the thermocouple and are effective in improving the measurement accuracy of the sample temperature, but they have the following problems. First, in the configuration of the above item, ice water is used to keep the temperature at the second junction constant at 0 ° C., but there is a problem of disappearance of ice water and supply. Further, in the configuration of the above paragraph, the sum of thermoelectromotive force generated at each junction between each metal wire for measuring the output voltage of the thermocouple and copper is completely equal to the thermoelectromotive force of the thermocouple. Therefore, it was difficult to correct the output voltage of the thermocouple based on the signal of the heat sensitive element and measure the correct sample temperature.

An object of the present invention is to provide a thermal analysis device which solves the above drawbacks and improves the accuracy of temperature measurement.

[0006]

The present invention was developed in order to solve the above-mentioned drawbacks, and the main constituents thereof are a metal wire 1 made of a first metal material, and the metal wire 1 described above.
A metal wire 2a made of a second metal material and joined to one end of the
A metal wire 2b made of a second metal material and joined to the other end of the metal wire 1; and a heat-sensitive element arranged in good thermal contact with a joining point between the metal wire 1 and the metal wire 2b. It is composed of elements.

[0007]

The metal wire 1 and the metal wires 2a and 2b are
A thermocouple consisting of two junction points A and B is formed, and the voltage between the metal wire 2a and the metal wire 2b is
It depends on the temperature of the junction A and the temperature of the junction B. on the other hand,
The thermosensitive element arranged in good thermal contact with the junction point B detects the temperature of the junction point B.

Therefore, the metal wire 2a and the metal wire 2b
By measuring the voltage between and and correcting the thermoelectromotive force value generated at the junction B on the basis of the signal of the thermosensitive element, the purpose of accurately measuring the temperature at the junction A is achieved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings showing one embodiment. In FIG. 1, 1 is an alumel wire,
The chromel wire 2a is joined at one end A of the alumel wire 1. On the other hand, another chromel wire 2b is joined to the other end B of the alumel wire 1, and the thermosensitive element 3 is attached to the junction point B in a good thermal contact state. They are located in one place where thermal fluctuations are relatively small. The chromel wire 2a and the chromel wire 2b are respectively joined to the copper wires 4a and 4b in order to measure the voltage between them, and the copper wires 4a and 4b are connected to the differential amplifier 5. The heat sensitive element 3 is connected to an amplifier 6, and the differential amplifier 5 and the amplifier 6 are both connected to a subtractor 7.

A sample 8 is arranged in the vicinity of the junction point A, and a heater 9 is arranged around the sample 8 for the purpose of adjusting the temperature of the sample 8. When the heater 9 is operated, the temperature of the joint A rises at the same time as the sample 8 and the joint A
A thermoelectromotive force is generated due to the Seebeck effect. Junction A
The difference between the thermoelectromotive force at the point B and the thermoelectromotive force at the junction point B is sent to the differential amplifier 5 as a voltage signal via the copper wires 4a and 4b. The differential amplifier 5 acts as an amplifier that amplifies a minute thermoelectromotive force difference signal.

On the other hand, the thermosensitive element 3 attached to the joint point B is arranged together with the joint point B in a location where the temperature is relatively stable, but the temperature changes due to various conditions, and The voltage signal to be measured is sent to the amplifier 6, and the voltage value per 1 ° C. of temperature is standardized by the amplification degree such that it matches the output of the differential amplifier. Subtractor 7
Outputs a voltage difference between the differential amplifier 5 and the amplifier 6 to output a voltage dependent on the temperature of only the junction A at which the output variation due to the temperature variation of the junction B is canceled. That is, the output of the subtractor 7 achieves the purpose of accurately measuring the temperature of the sample 8.

In the description of the present embodiment, the correction of the thermoelectromotive force signal by the signal of the thermosensitive element has been described based on the concept of voltage comparison. However, after the signal of the thermosensitive element is once converted into a temperature value, this temperature value is converted. The object can also be achieved by subtracting the thermoelectromotive force (voltage value) corresponding to the original thermoelectromotive force signal, and in particular, when a thermocouple having a large non-linear degree of thermoelectromotive force characteristics is used, The measurement accuracy is further improved.

Although not specifically mentioned in the above-mentioned embodiments, the object of the present invention can be achieved even if the kind of the metal material such as alumel, chromel, copper, etc. shown in the embodiments is changed. Of course. Further, as the heat sensitive element, a platinum resistor, a thermistor, or another temperature IC
Etc., and any of them can be used as a heat-sensitive element for achieving the object of the present invention. Moreover, the present invention can be applied to improve the measurement accuracy of the heater temperature other than the samples generally used in the thermal analyzer.

[0014]

As described above, according to the present invention, the joining point A
Since the junction point B made of the same material as in 1 is provided and the temperature of the junction point B is accurately measured by the thermosensitive element 3, the cold junction compensation of the thermocouple is performed, so that the thermoelectromotive force of the thermocouple is also detected. Moreover, the temperature of the sample 8 can be accurately measured.

Further, thermocouple wires (chromel wires) 2a, 2
Since the dissimilar metal joint portion from b to the differential amplifier 5 can be configured completely symmetrically, the device configuration becomes complicated, and even when various connectors are used, heat generated at the dissimilar metal joint portion is generated. The powers cancel each other out, the generation of stray electromotive force can be minimized, and the temperature of the sample 8 can be measured accurately. Further, the present invention brings about the same effect for improving the accuracy of heater temperature measurement.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional example.

FIG. 3 is an explanatory diagram showing another conventional example.

[Explanation of symbols]

 1 Alumel wire 2a, 2b Chromel wire 3 Thermal element 4a, 4b Copper wire 5 Differential amplifier 6 Amplifier 7 Subtractor 8 Sample 9 Heater

Claims (1)

[Claims] 1. A metal wire 1 made of a first metal material, a metal wire 2a made of a second metal material joined to one end of the metal wire 1, and another end of the metal wire 1 joined together. A metal wire 2b made of a second metal material, and a heat-sensitive element arranged in a good thermal contact state with respect to a joining point of the metal wire 1 and the metal wire 2b are provided, and the metal wire 2a and the metal wire are provided. Line 2
A thermal analysis device, characterized in that the temperature at the junction between the metal wire 1 and the metal wire 2a is measured based on a voltage signal between the metal wire 1 and the heat sensitive element.