JPH0131585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential thermal analysis apparatus. Differential thermal analyzers usually have a sample side disk and a reference side disk arranged on the same plane, but this configuration requires a large heating furnace, so in order to downsize the heating furnace, the sample side disk and the reference side disk are arranged side by side. A differential thermal analyzer has been proposed in which reference side disks are arranged vertically. The present invention particularly relates to a thermal analysis apparatus in which the latter heating furnace is miniaturized.

In the thermal analysis device described above in which the sample side disk and the reference side disk are arranged vertically, the radiant heat from the furnace directly affects the sample, so the effect of heat radiation from the heating furnace is different between the sample cell and the reference cell. However, there is a drawback that the baseline of the measurement output tends to be distorted, especially when the sample shrinks or changes color in a high temperature region. The present invention aims to eliminate the above-mentioned drawbacks of this type of thermal analysis device.

In the present invention, an upper heat shield plate and a lower shield plate are provided at appropriate intervals above and below both sample and reference disks arranged one above the other, and a thermoelectric plate is welded to the lower disk. A differential thermal analysis device characterized in that the lead wires of the pair are made approximately the same length as the lead wires of the thermocouple welded to the upper disk to have some slack, and the slack is bent to the side. I will provide a. The heat shield plate described above prevents the radiant heat from the heating furnace from directly entering the sample or reference cell, and allows both the sample and reference material to be heated by the atmosphere inside the furnace, making the surrounding conditions of both uniform. It is something to do. If the thermocouple lead wire welded to the lower disk is straight, it will be shorter than the thermocouple lead wire of the upper disk, but if this is done, the effect of heat conduction of the lead wire will be different between the upper and lower disks. The lead wires of the thermocouples on the lower disk are slackened so that the lengths of the leads of both thermocouples are approximately the same to equalize the heat conduction effect. With such a configuration, the surrounding conditions of both the upper and lower disks are made uniform, so that according to the present invention, a stable baseline can be obtained up to high temperatures. The present invention will be explained below with reference to Examples.

FIG. 1 shows an embodiment of the invention. 1 is a heating furnace. 2 is a sample side disk, 3 is a reference side disk, 4 is a heat shield plate installed below the reference side disk, 5 is a heat shield plate placed above the sample side disk, and these upper and lower heat shield plates are They are connected by struts 6, and the lower boss portion of the lower shielding plate 4 is fitted onto the upper end of the insulator 7, so that the entire structure is supported. Thermocouple lead wires 8 and 9 are welded to the disks 2 and 3, respectively, and the lower ends of these lead wires are individually inserted into four holes in the insulator 7 to connect the struts that support the disks 2 and 3. Also serves as. The lead wire 9 of the thermocouple welded to the lower reference side disk 3 is slackened and bent laterally 10. Therefore, the two disks 2 and 3 have the same conditions regarding heat conduction by the thermocouple lead wires. 11 is a sample cell placed on the sample side disk 2;
12 is a reference material placed on the reference side disk 3, and there is a notch 1 for escape from the lead wire of the thermocouple 8.
3 is provided. Note that the influence of radiant heat is large when it acts on the sample from above, so in some cases, only the upper shielding plate may be used.

FIG. 2 schematically shows the connection of thermocouples 8 and 9. The curvature of the baseline due to radiant heat from the heating furnace can be improved to some extent by directly covering the sample cell with a lid. However, if this is done, it becomes difficult for volatile gases from the sample to escape, and contact between the sample and the atmosphere becomes poor, resulting in the temperature characteristics of the sample itself being different from those in the sample open state. In the case of the present invention, the shielding plate is placed apart from the sample and does not impede the circulation of the atmosphere around the sample, so the above-mentioned problem does not occur. The differential thermal analyzer according to the present invention has the above-described configuration, and the shielding plate prevents the radiant heat from the furnace from directly affecting the sample, equalizes the external conditions between the sample and the reference material, and The thermal effects of the pair are equalized for the sample and the reference substance, so even though it is a compact device, the baseline stability is high even up to high temperatures. Although thermal analysis is performed at temperatures below 0° C., the shielding plate acts as a resistance to convection in the furnace, so that it also has the effect of reducing noise due to convection in such a low-temperature region. In the above embodiment, the upper and lower shielding plates are connected by a support, but the upper shielding plate may have legs and be placed on the lower shielding plate. The shielding plate may be configured as a cup-shaped perforated plate having a large number of small holes, so as to cover the entire upper and lower disks. In this way, the upper and lower disks are placed in a small space surrounded by the shielding plate, and temperature fluctuations due to convection inside the furnace are eliminated, and since the inside of the shielding plate is a small space, the ambient temperature is Since the shielding plate is a perforated plate, the inside of the shielding plate is not a completely isolated space, but there is some exchange with the atmosphere inside the furnace, and direct radiation can be shielded while following the average temperature inside the furnace. It is.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a device according to an embodiment of the present invention, and FIG. 2 is a wiring diagram of a thermocouple in the same device. 1... Heating furnace, 2... Sample side disk, 3...
Reference radiation disk, 4... Lower shielding plate, 5... Upper shielding plate, 8, 9... Thermocouple lead wire, 10...
Slack part of thermocouple 9.

Claims (1)

[Claims] 1 In the furnace, arrange the sample disk and reference disk one above the other, place a shielding plate at least above and below both disks, and weld thermocouples to both the sample side and reference side disks, respectively. A differential thermal analyzer characterized in that the lead wire of the thermocouple of the lower disk is slackened so that it has approximately the same length as the lead wire of the thermocouple of the upper disk.