JPS62195549A - Differential scanning calorimeter - Google Patents

Abstract

PURPOSE:To obtain a differential scanning calorimeter having high sensitivity and high accuracy by providing a heating furnace having an H-shaped section, a thermal conductor projecting at the center of the furnace bottom plate and thermopiles disposed atop the thermal conductor symmetrically with the furnace section. CONSTITUTION:The electrical insulating conductor BeO3 is fixed to the center of the bottom plate 2 of the heating furnace 1 and many pairs of the thermopiles 4 consisting of constantan wires 8 and chromel wires 9 are disposed symmetrically with the BeO as a center and are fixed to the BeO in contact therewith by a bar- shaped plate. Sample cells 5a, 5b which are thermal conductors having an electrical insulating characteristic are welded to the right and left of the contact points 10 of the thermocouples. Chromel wires 6a, 6b and alumel wires 7a, 7b are welded to the first and final contact points A, B of the thermopiles 4. Temp. control is executed by a heater wound around the furnace. A sample to be inspected is placed on the cell 5a and a reference material on the cell 5b and the temp. difference between both is detected by the thermopiles 4. Since many pairs of the thermopiles are used, even the small temp. difference can be amplifier and recorded without being limited by the noise level of an amplifier and the differential scanning calorimeter having the high sensitivity and high accuracy is obtd.

Description

[Detailed description of the invention] C Industrial application field] The present invention relates to a differential scanning calorimeter.

[Summary of the invention]

The present invention aims to stabilize the hair line and improve the sensitivity of a differential scanning calorimeter. A thermal conductor to be formed and a thermopile installed on the upper surface of the thermal conductor so as to maintain a symmetrical position with respect to the cross section of the heating furnace.

The above purpose is achieved by suppressing differential scanning calorimetry baseline fluctuations caused by the temperature gradient of the heating furnace, and by detecting the temperature difference between the sample side and the reference material side using a thermopile and generating a large thermoelectromotive force. This is what we achieved.

[Conventional technology]

Conventionally, as disclosed in Japanese Utility Model Application No. 60-64250, this type of invention has a configuration as shown in FIG. 3.

[Problem that the invention seeks to solve]

In the above conventional technology, since the constituent metal of the thermocouple is integrally used as a heat conductor installed on the bottom plate of the heating furnace, a pair of differential thermocouples are used to detect the temperature difference between the sample side and the reference material side. The electromotive force cannot be generated. When this signal is amplified by an amplifier, a signal below the noise level of the amplifier cannot be amplified, resulting in a drawback of insufficient sensitivity.

[Means for solving problems]

The present invention was developed to eliminate the above-mentioned drawbacks, and includes a heating furnace having a T-shaped cross section, a heat conductor forming a convex portion at approximately the center of the bottom plate of the heating furnace, and an upper surface of the heat conductor. and a thermopile provided so as to maintain a symmetrical position with respect to the cross section of the heating furnace.

〔Example〕

FIG. 1 shows a three-dimensional cross-sectional view of an embodiment of a differential scanning calorimetry needle according to the present invention. Further, FIG. 2 shows a wiring diagram of the thermopile of the embodiment.

1 indicates a heating furnace having a cross section of
At approximately the center position on the upper side, there is a thermal conductor 3 that is convex with respect to the bottom plate surface, is a thermal conductor, and is electrically insulating at least on the upper surface (for example, beryllium oxide or anodized aluminum). , electrically insulating ceramic deposited on silver, etc.) is placed and fixed. The thermal conductor 3
A thermopile 4 (four pairs of chromel and constancan in the embodiment) consisting of many pairs of thermoelectric wires is fixed on the upper surface of the heating furnace 1 in a position parallel to the bottom plate surface of the heating furnace 1. Further, each contact portion 10 of the thermopile 4 is connected to the thermal conductor 3,
arranged in a symmetrical shape. The thermopile 4 is a second
As shown in the figure, it is formed from a first metal wire 8 (Constankun) and a second metal wire 9 (Chromel).

Further, each contact portion 10 of the thermopile 4 is provided with a thermally conductive and electrically insulating plate-shaped sample cell 5a, 5b.
is 1 on each left and right ([1i! is fixed. Said heating furnace 1
The means for fixing the bottom surface 2 and the thermal conductor 3 may be mechanical joining means (not shown) such as screws, silver solder, or an integral part.
However, as means for fixing the thermal conductor 3 and the thermopile 4, a rod-shaped holding plate (not shown) and the thermal conductor 3 are used.
The thermopile 4 is sandwiched and screwed, or the thermopile 4 is placed on the top surface of the heat conductor 3.
A metal film is deposited in a linear form as many as the number of wires, and
Mechanical joining means (not shown) such as welding the respective strands of the thermopile 4 and the sample cell 5a
, 5b is the means for fixing the sample cells 5a, 5b.
On the back side, as many as the contact parts IO of the thermopile 4,
A metal film is deposited in spots and fixed using mechanical joining means (not shown) such as welding to the thermopile contact portion 10. All of the above mechanical joints maintain good thermal contact. Moreover, the sample cell 5a
, 5b of the first contact A of said thermopile 4 joined to
And at the last contact point B, second gold wires 6a, 6b (chromel) for extracting electric signals and a third metal wire 7a are connected.
, 7b (alumel) are welded.

The temperature of the heating furnace 1 is controlled by a temperature control device (not shown) using a heater (not shown) wound around the heating furnace to raise the temperature, lower the temperature, or maintain a constant temperature. On the other hand, the sample cell 5a contains a test sample (not shown),
The sample cell 5b contains a thermally stable reference material (not shown).
is mounted, and the temperature difference between the two is detected by the thermopile 4.

The inside of the heating furnace 1 is constructed symmetrically with respect to the two sample cells 5a and 5b, and the bottom plate 2 and the thermal conductor 3 of the heating furnace 1 act as a thermoelectric meter. Since a mechanically and physically fixed thermopile is interposed between the thermal conductor 3 and the sample cells 5a and 5b, if the temperature difference detection signal is appropriately calibrated by measuring a known sample, The configuration shown in FIG. 1 functions as a well-known heat flux type differential scanning calorimeter. ,
and flows through the thermopile 4 to the sample cells 5a, 5b. The heat flow path at this time is restricted by the thermal conductor 3, and as is well known, this structure greatly contributes to the stability of the baseline of differential scanning calorimetry.

On the other hand, a second metal wire 6a and a third metal wire 6b for extracting electric signals, which are welded on the back surface of the sample cell 5a, form a thermocouple, and this thermocouple allows the temperature of the test sample to be adjusted. Detected.

On the other hand, when converting the temperature difference between the sample cells 5a and 5b into an electrical signal, amplifying it with an amplifier (not shown), and recording it on a recorder (not shown), etc., the level at which the amplification is meaningful as data is the temperature difference. It is necessary that the electrical signal detected as a noise level is higher than the noise level of the input signal of the amplifier used.

Now, suppose that the noise level for the input signal of the amplifier used is 6 μV, the thermocouples used to detect the temperature difference are Chromel and Constanqun, and the thermoelectromotive force per pair of thermocouples is 60 μV/'C. Then, if there is a pair of thermocouples that detect the temperature difference, 6μ■/60μV/'C = 0.1
Even if a temperature difference of less than ℃ is amplified, it cannot be distinguished from the noise level of the amplifier and cannot be detected. However, if the thermocouple that detects this temperature difference is made into a thermopile, for example 4
When paired, the electromotive force generated per 1°C temperature difference is 4
It becomes 240μV/'C, which is 6μ■/240
Temperature differences up to μv/”c = 0.025°C can be detected below the noise level. This has the effect of substantially improving the sensitivity of the differential scanning calorimeter.
As an embodiment of this invention, a case has been described in which the thermocouple wire itself of the thermopile 4 is used as a path for heat flow from the heating furnace bottom plate 2 and heat conduction pair 3 as thermocouples to the sample cell 5a5b. It goes without saying that similar effects can be obtained by using a ceramic material or the like (for example, alumina sintered body, beryllium oxide sintered body) with multiple thermocouples attached thinly for the heat flow path described above.

〔Effect of the invention〕

As described above, according to the present invention, since the temperature difference between the sample cells in the heating furnace is detected by the thermopile, the detection signal of the electromotive force generated for the same temperature difference is large.
Even small temperature differences can be amplified and recorded without being affected by the noise level of the amplifier, making it possible to realize a differential scanning calorimeter with high sensitivity and high temperature.

[Brief explanation of drawings]

FIG. 1 is a sectional three-dimensional view showing an embodiment of the present invention, FIG. 2 is a thermopile connection diagram of the embodiment, and FIG. 3 is a sectional view of a conventional example. 1... Heating furnace 2... Heating furnace bottom plate 3... Thermal conductor 4... Thermopiles 5a, 5b... Sample cells 6a, 6b... Second metal wires 7a, 7b...・Third metal wire 8...First metal wire 9...Second metal wire 10...Contact part A...First contact B...Last contact 11... -Heating furnace 12...Heating furnace bottom plate 13...Thermal conductors 15a, 15b...Sample cells 16a, 16b...Second metal strands 17a, 17b...Third metal strands that's all

Claims (1)

[Claims] a heating furnace having an H-shaped cross section; a heat conductor having a convex bottom at a substantially central position on a bottom plate of the heating furnace; and a heat conductor provided on an upper surface of the heat conductor at a symmetrical position with respect to the interior of the heating furnace. A differential scanning calorimeter consisting of multiple thermopiles.