JPH01187422A - Thermometer for low temperature - Google Patents

Abstract

PURPOSE:To measure temperature over a wide range from low temperature to extremely low temperature by arranging superconducting materials, providing electrodes so that they are connected in parallel or series, and taking a measurement based upon the value of a current flowing among them. CONSTITUTION:The thermometer 1 is mounted on the surface of a body S to be measured to measure its temperature. Then the superconducting materials 3-6 with which a base plate 2 is coated become zero in resistance when reaching their different critical temperature values. Therefore, a superconducting material whose critical temperature corresponds to the measured temperature decreases in area resistance and the current flows between electrodes 7 and 8. Its current value is measured to measure the temperature and a voltage applied at this time may be a fine voltage by various batteries, etc. Further, when superconducting materials are used for lead wires 9a and 9b, current loss is eliminated and the life of an in-use battery is prolonged greatly to obtain an economical merit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a low temperature thermometer for measuring low or extremely low temperatures.

[Prior Art] Hitherto, there are almost no known thermometers that can accurately measure low or extremely low temperatures within a membrane over a wide range. -100℃
Thermistors made of SiC crystals and 5nSe thin films are used in low-temperature thermometers, but these low-temperature thermometers have a long time constant of 30 to 60 seconds, making accurate temperature measurement difficult. be.

Further, as a thermometer for extremely low temperatures, there is a resistance thermometer using a Ge semiconductor element. This resistance thermometer indirectly detects temperature by measuring its electrical resistance using the four-terminal method. However, since this Ge semiconductor element has helium gas sealed in its capsule, its thermal conductivity is low and accurate temperature measurement is difficult. Furthermore, since extremely thin lead wires are used in the wiring inside the capsule in order to suppress the intrusion of heat, there is a risk that the wires will break if even a small amount of excessive current flows.

While a variety of thermometers that can measure temperatures from room temperature to high temperatures have been manufactured to date, there are currently no thermometers that can accurately measure a wide range of temperatures from low to extremely low temperatures. You can say that.

[Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a low temperature thermometer that can measure a wide range of temperatures from low temperatures to extremely low temperatures by using a superconducting material in the low temperature temperature detection part. It's about doing.

[Summary of the Invention] The gist of the present invention to achieve the above object is to arrange a plurality of superconducting materials having different superconducting critical temperatures at low temperatures, and to connect these superconducting materials in parallel or in series. This low-temperature thermometer is characterized in that electrodes are provided so as to be connected to the low-temperature thermometer, and the low-temperature measurement is performed based on the value of the current flowing between these electrodes.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a plan view of the low temperature thermometer 1, and FIG. 2 is a sectional view. In the drawing, thin film-like superconducting materials 3 to 6 are coated on a substrate 2 made of metal, for example, and these superconducting materials 3 to 6 have different superconducting critical temperatures and are arranged adjacent to each other.

The superconducting materials 3 to 6 include, for example, a superconducting material 3 made of Nb3Ge that reaches its critical temperature at 23, a La-Ba-Cu-0 based ceramic that reaches its critical temperature at 30, or Y:0. .4, superconducting material 4 with a composition ratio such as Ba: 0.6, Cub: 2.22, and Y reaching a critical temperature at 98.
-Superconducting material made of Ba-Cu-0 based quaternary alloy 5.1
A superconducting material 6 made of a Y-Ba-Cu-0 based quaternary alloy which reaches its critical temperature at 23 is used.

Electrodes 7.8 are connected to both ends of these superconducting materials 3 to 6 so that the superconducting materials 3 to 6 are connected in parallel, and lead wires 9a and 9b are connected to the electrodes 7.8, respectively. A synthetic resin coating member 10 typified by epoxy resin or the like is overcoated to protect the superconducting materials 3 to 6 and the electrodes 7.8. For this synthetic resin covering member 10, a material is selected which also has the purpose of fixing the electrode 7.8 and the lead wires 9a, 9b. Further, it is preferable to use an alloy with good thermal conductivity such as Au, Ag, Cu, or stainless steel, which has good thermal conductivity, for the substrate 2.

In addition, when obtaining an arbitrary critical temperature between 98 and -123, by selecting various composition ratios of the Y-Ba-Cu-0 system, superconducting material can be obtained.

Furthermore, even in superconducting materials other than those mentioned above, it is possible to achieve a desired critical temperature by changing the composition ratio of the alloy. Therefore, in order to measure temperature in a low temperature region, it is sufficient to use superconducting materials made of ceramics or crystals having various compositions and composition ratios.

Figure 3 shows a case where temperature measurement is carried out by gluing the low temperature thermometer 1 to the surface of the object to be measured S. When each of the superconducting materials 3 to 6 reaches a predetermined critical temperature, the corresponding superconductor material 3
~6 resistance becomes zero.

Therefore, a current flows by the amount that the sheet resistance of the superconducting material decreases corresponding to the critical temperature, so temperature can be measured by measuring this current value. That's enough. Furthermore, if the lead wires 9a and 9b are also made of superconducting material, there will be no current loss, so the life of the battery used will be significantly extended, and the life of the thermometer will also be extended, which is economically advantageous.

The temperature measurement range of the low temperature thermometer 1 obtained in this example is shown in Table 1.

Table 1 Superconducting material Temperature K Nb3Ge 23L a:
0.4, Ba: 0.6, CuO: 2.22 30
Y, Ba2, Cu207 98Y: 0.
4, B a :0. f3, Cuo: 2.22 123 That is, as shown in Table 1, this low-temperature thermometer 1 can measure temperatures from as low as 23, which is close to the liquid hydrogen temperature (20K), to 1.
Temperatures down to 23K (-150C) can be measured.

In the previous example, an example was shown in which four types of superconducting materials were selected and the measurement temperature was set at four points, but for example, La-B
By changing the composition ratio of the a-Cu-0 series and Y-Ba-Cu-0 series superconducting materials, the critical temperature of the superconducting materials changes significantly, which allows measurement within the measurement temperature range. The number of points can be increased to make the measurements more continuous. For example, in the case of Y-Ba-Cu-0-based superconducting material, it is possible to measure a wide range of temperatures from 98 to 123, so by changing the composition ratio,
If a superconducting material having a critical temperature for each is created, the four types of superconducting materials used in the previous example can be added to four more types, making it possible to measure temperature in eight steps.

In addition, as shown in FIG. 4, using a superconducting material 11 made of Nb3Sn, the temperature of liquid hydrogen was 20K, La: 1.85,
Superconducting material 11.1 for measuring liquid nitrogen temperature of 77K using superconducting material 12 made of Sr: 0.5 and CuO2
A low-temperature thermometer for two-point measurement with 2 having a cylindrical two-layer structure is obtained.

In this case, in terms of the circuit, superconducting materials 11 and 12 are connected in series, and electrodes 13 and 14 are provided on both sides of the superconducting materials 11 and 12. In addition, the critical temperatures of superconducting materials 11 and 12 are 18
K, at 56.

As in the embodiments described above, by arbitrarily arranging multiple points of superconducting material having a specific critical temperature, it becomes possible to measure temperatures at multiple points from low to extremely low temperatures. Furthermore, other low-temperature thermometers of any shape can be manufactured depending on the purpose.

In addition, in terms of dimensions, a superconducting material with a width of several JLm can be used, making it possible to realize an extremely compact low-temperature thermometer.

[Effects of the Invention] As explained above, the low temperature thermometer according to the present invention can be used at extremely low temperatures below -100°C by arbitrarily selecting the type of superconducting material, the composition ratio, and the changes in the area resistance ratio. It becomes possible to measure up to In addition, by changing the type and composition ratio of the superconducting material, the measurement temperature step is based on the change in sheet resistance, making it possible to arbitrarily measure temperature in multiple steps.
Temperatures from low to extremely low temperatures can be measured almost continuously.

[Brief explanation of the drawing]

The drawings show an embodiment of the low-temperature thermometer according to the present invention.
The figure is a plan view, FIG. 2 is a sectional view taken along line I--n in FIG. 1, FIG. 3 is a perspective view of the temperature measuring state, and FIG. 4 is a sectional view of the circular thermometer. Reference numeral 1 is a thermometer, 2 is a substrate, 3 to 6.11.12 are superconducting materials, 7.8.13.14 are electrodes, 9a and 9b are lead wires, and IO is a synthetic resin coating member. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. Arrange multiple superconducting materials with different superconducting critical temperatures at low temperatures, provide electrodes to connect these superconducting materials in parallel or in series, and calculate the value of the current flowing between these electrodes. A low-temperature thermometer that measures low temperatures based on .