JP7041885B2 - Temperature detection mechanism, electronic thermometer and deep thermometer - Google Patents

Description

The present invention relates to a temperature detection mechanism including a temperature sensor in which gallium is closely attached, an electronic thermometer and a deep thermometer.

A technique that mainly uses the melting point of a pure metal such as silver, aluminum, or copper as a temperature standard for thermometer calibration is known (Patent Document 1). In this technique, pure metal is vacuum-sealed, leaving a space inside a ceramic container with a temperature sensor insertion hole. The container is provided with an insertion hole, and the temperature sensor is inserted into this hole and brought into contact with the side surface of the container to measure the temperature of pure metal.
In addition, the melting point of high-purity gallium is about 29.76 (℃), and it is shown in a 1970s paper (Non-Patent Document 1) by Sostman et al. That it is useful as a temperature standard near room temperature.

Japanese Unexamined Patent Publication No. 08-15506

H.E. Sostman, Melting point of gallium as a temperature calibration standard. Review of Scientific Instruments. Published February 1977 vol. 48, p127-130.

However, when gallium is used as a temperature standard, the technique of Patent Document 1 has the following problems.
That is, when measuring the temperature of gallium put in a container with a temperature sensor in contact with the side surface of the container, it is necessary to sufficiently increase the heat capacity of gallium and the container with respect to the heat capacity of the sensor in order to keep the gallium and the sensor at an isothermal temperature. There is a problem that the volume of gallium and the container becomes large.
In particular, in a small device such as an electronic thermometer, it is necessary to house gallium and a mechanism for holding gallium in the temperature sensitive part of the electronic thermometer, so that the container containing gallium cannot be stored in the temperature sensitive part. There is.
If the container containing gallium is reduced to a size that can be accommodated in the temperature sensitive part, the temperature sensor also needs to be relatively small, so the thermistor normally used in electronic thermometers cannot be used as a temperature sensor. The problem arises.

In consideration of such a problem, the present invention has a temperature detection mechanism, an electronic thermometer and a deep thermometer that enable miniaturization and high-precision temperature measurement without aging by using a sensor in close contact with gallium. The purpose is to provide.

The temperature detection mechanism of the present invention uses gallium as a temperature standard, and in a temperature detection mechanism having a function of automatically calibrating the detected temperature when the detected temperature of the sensor passes through the melting point of gallium, the sensor is used. , A sensor main body, a gallium layer that is in close contact with the periphery of the sensor main body, and a protective layer that covers the periphery of the gallium layer , and the gallium layer is a resin layer in which microcapsules containing gallium are dispersed. It is characterized by being composed of.
The electronic thermometer of the present invention is characterized by including the above-mentioned temperature detection mechanism.
The deep thermometer of the present invention is characterized by including a heat flow compensation system using the temperature detection mechanism.

In the present invention, since the gallium layer is brought into close contact with the sensor main body, it becomes easy to keep the gallium and the sensor main body at an isothermal temperature as compared with the case where gallium is put in a container as in the conventional case. Since the gallium layer and the sensor main body can be made smaller, it can be housed in the temperature sensitive part of an electronic thermometer, for example.
Further, when the gallium layer is formed by dispersing the gallium-encapsulated microcapsules, the temperature detection mechanism can be easily manufactured and the wall material of the microcapsules prevents impurities from being mixed in the gallium to change the melting point. It is possible to achieve high accuracy without aging.

Schematic diagram showing a temperature detection mechanism and an electronic thermometer in the first embodiment Block diagram showing the configuration of the control unit Graph showing the relationship between temperature output and elapsed time Schematic diagram showing a temperature detection mechanism and an electronic thermometer in the second embodiment Overview of the prototype thermistor in the examples Cross-sectional photograph of the prototype thermistor Graph showing the results of body temperature measurement experiments Of the results of the heat transfer confirmation experiment from the lead wire, the graph showing the result without heat insulation (a) and the graph showing the result with heat insulation (b)

[First Embodiment]
The first embodiment of the temperature detection mechanism 1 of the present invention and the electronic thermometer 2 including the temperature detection mechanism 1 will be described.
As shown in FIGS. 1 and 2, most of the temperature detection mechanism 1 is housed in the temperature sensing portion 10 of the electronic thermometer 2.
The temperature detection mechanism 1 uses gallium as a temperature standard and has a function of automatically calibrating the detection temperature of the sensor.

The sensor is roughly composed of a sensor main body 20, a gallium layer 21, a protective layer 22, and a control unit 23.
As the sensor main body 20, a general temperature sensor can be used, and examples thereof include, but are not limited to, those provided with a thermistor and a pn junction diode. For example, resistance temperature detectors such as platinum can also be used.

The gallium layer 21 is formed in close contact with the periphery of the sensor main body 20. As a method of bringing the gallium layer 21 into close contact with the periphery of the sensor main body 20, for example, there is a dip method in which the sensor main body 20 is immersed in liquid gallium, taken out, and allowed to cool and solidify. By bringing the gallium layer 21 into close contact with the sensor main body 20, it becomes easy to keep the gallium layer 21 and the sensor main body 20 at an isothermal temperature.
Gallium is preferably as pure as possible, but may also be an alloy with indium or tin.

The protective layer 22 is provided to cover the circumference of the gallium layer 21.
The protective layer 22 is preferably made of a flexible material such as polypropylene or Teflon (registered trademark). By giving the protective layer 22 flexibility, it is possible to absorb the volume change (expansion / contraction) at the time of the phase transition of gallium due to the temperature change.
The control unit 23 receives the temperature output X from the sensor main body unit 20, performs arithmetic processing, and then outputs the corrected temperature. The control unit 23 is roughly composed of a temperature output unit 23a, a melting point detection unit 23b, a correction value correction unit 23c, a correction temperature output unit 23d, and a temperature display unit 23e.

したがって、平坦部分の期間にセンサーに流入する熱量Q(J)は次の数式2となる。

平坦部分においてはセンサー温度が変化しないので、流入した熱量はすべて潜熱で吸収される。したがって、センサーに密着させたガリウムの質量をm(g)とすれば、ガリウムの融解における潜熱は約80(J/g)であることから、平坦部分の終端においては次の数式3となる。

したがって数式2及び3より次の数式4が得られる。

Next, the principle of the temperature detection mechanism 1 will be described.
When the electronic thermometer 2 placed at room temperature of 20 ° C is attached to the body at 37 ° C, the measured temperature approaches the body temperature almost exponentially with the passage of time as shown in Fig. 3. Then, when the measured temperature passes the melting point of gallium, 29.76 (° C), gallium begins to melt. Latent heat is absorbed and kept at a constant temperature until the gallium is completely melted, so that a flat portion is formed in the middle of the temperature rise curve.
The time length d (s) of the flat part is determined by the structure of the sensor. That is, the sensor temperature is T1 (° C), the temperature of the surrounding medium is T2 (° C), the thermal conductivity of the protective layer material is k (W / m · K), and the thickness of the protective layer 22 is L (m). Assuming that the surface area of the sensor is A (m ² ), the rate of increase of the medium temperature T2 around the sensor is λ (K / s), and the elapsed time after the sensor reaches its melting point is t (s), then after reaching the melting point The heat inflow F (J / s) into the sensor is as shown in Equation 1 below.

Therefore, the amount of heat Q (J) flowing into the sensor during the period of the flat portion is given by the following equation 2.

Since the sensor temperature does not change in the flat part, all the inflowing heat is absorbed by latent heat. Therefore, if the mass of gallium in close contact with the sensor is m (g), the latent heat in melting gallium is about 80 (J / g), so the following equation 3 is obtained at the end of the flat portion.

Therefore, the following formula 4 can be obtained from formulas 2 and 3.

As a practical example, the diameter of the sensor is 2 (mm), the length is 1 (mm) (A = 6.3 × 10 ^-6 m ² ), m is 5 (mg), L is 0.1 (mm), k. If is 0.5 (W / m · K) and λ is 0.1 (K / s), the time of the flat part is about 16.3 (s). Even if the size and shape of the sensor are different, the time d of the flat portion can be adjusted by appropriately setting the mass m of the gallium in close contact. If a flat part for an appropriate time is obtained, it can be expected to calibrate with an absolute accuracy of 0.01 (° C) near 30 (° C) by automatically adjusting the output of the measurement system at that time to 29.76 (° C). ..
From this result, if the sensor has a shape similar to the spherical sensor used in the calculation, the required mass of gallium is about 5 mg, and even if the protective layer is included, it can be sufficiently stored in the temperature sensitive part at the tip of a normal electronic thermometer. ..

Next, an example of the operation of the control unit 23 will be described.
First, the temperature output unit 23a connected to the sensor body unit 20 outputs the temperature output X. The melting point detection unit 23b receives the temperature output X, and sets the output P to 0 while the temperature output X rises smoothly, and sets the output P to 1 while detecting the flat portion. When the output P is 0, the correction value correction unit 23c holds the output P unchanged, and when the output P is 1, replaces the correction value output Y with (29.765-X). The correction temperature output unit 23d outputs the correction temperature as the sum of the temperature output X and the correction value output Y, and the temperature display unit 23e displays the correction temperature.
As another example of the operation of the control unit 23, for example, when analyzing the time course of the body temperature after recording the body temperature for a long time, a flat portion near the melting point of gallium is extracted from the read temperature data and the flat portion thereof is extracted. All data should be corrected so that the output value of the point is 29.76 (° C). However, when the temperature recording is sampling data, the sampling interval needs to be sufficiently shorter than the length of the flat portion.

[Second embodiment]
Next, the temperature detection mechanism of the present invention and the second embodiment of the electronic thermometer provided with the temperature detection mechanism will be described, but the same reference numerals will be given to the parts having the same configuration as the first embodiment. The explanation will be omitted.
As shown in FIG. 4, the temperature detection mechanism 3 and the electronic thermometer 4 of the present embodiment are characterized in that the gallium layer 31 is composed of a resin layer in which microcapsules 30 containing gallium are dispersed.
By using the microcapsules 30, the temperature detection mechanism 3 and the electronic thermometer 4 can be easily manufactured, and the wall material of the microcapsules 30 can prevent impurities from being mixed in gallium and changing the melting point, resulting in high accuracy. Can be kept.
A paper on the manufacturing technology of microcapsules containing gallium-indium alloy (BJ Blaiszik et al., Microencapsulation of gallium-indium (Ga-In) liquid metal for self-healing applications. J. Microencapsul. 2014 vol. 31, p350 As described in ~ 354.), It is a well-known technique, and by using this technique, microcapsules 30 having gallium as a core material can be manufactured.

[Third embodiment]
Next, a deep thermometer using the temperature detection mechanisms 1 and 3 of the present invention will be described.
In a deep body thermometer that uses a heat flow compensation system, two temperature sensors installed on both sides of the heat insulating layer detect the temperature difference in order to detect the heat flow, and heat one side so that the temperature difference becomes zero. This achieves near-perfect insulation. At this time, in order to perform heat flow compensation with high accuracy, it is necessary to minimize the relative error between the two temperature sensors, and the temperature detection mechanisms 1 and 3 of the present invention are effective.
In the temperature detection mechanisms 1 and 3 of the present invention, it is necessary for the sensor temperature to pass through the melting point of gallium. As it rises towards body temperature, it can be automatically calibrated using two temperature sensors if the room temperature is below 29 ° C.

[Prototype of gallium-filled thermistor]
Liquid gallium has the problem of embrittlement of most metals and very high wettability and difficulty in handling. Therefore, in order to solve this problem, we independently devised a method of coating the head of a glass-coated thermistor with gallium and further protecting it with polyurethane, enabling the realization of a gallium-filled thermistor. Fig. 5 shows an overview of the prototype thermistor, and Fig. 6 shows a cross-sectional photograph. From FIG. 6, it can be confirmed that the gallium layer around the thermistor is firmly enclosed by the polyurethane layer.
[Experiment of body temperature measurement using a gallium-filled thermistor]
Cool the gallium-filled thermistor in the refrigerator to solidify the gallium. Immediately before the measurement, the thermistor head was taken out of the refrigerator, the gallium-encapsulated thermistor head was sandwiched between the medial side of the elbow joint or the axilla, and the temperature change at that time was measured at 5-second intervals by a temperature data logger (CT-620BT, Custom Co., Ltd.). The results are shown in Fig. 7. From this result, a flat temperature part, which is considered to be caused by the phase transition of gallium, was observed, and the validity of the newly devised method was confirmed.
[Heat transfer confirmation experiment from lead wire]
Since it was considered that the heat transfer of the lead wire might affect the temperature measurement accuracy of the phase transition part, we prepared a heat-shrinkable tube with enhanced heat insulation effect and conducted a measurement experiment of flat part temperature detection under the same conditions. rice field. The results are shown in Figure 8. From this result, it can be seen that there is a difference in the temperature of the flat portion and the duration of the flat portion depending on the presence or absence of heat insulation of the lead wire. Specifically, the temperature at the flat temperature portion is closer to the gallium melting point of 29.7646 ° C in the case without heat insulation (Fig. 8 (a)) than in the case with heat insulation (Fig. 8 (b)). In addition, the duration of the flat temperature portion is longer with heat insulation. It is considered that this is because the temperature of the lead wire is lower than that of the thermistor head part and heat flows out when the heat is insulated, and it seems that there is no temperature difference between the thermistor head and the lead wire part when prototyping the prototype. It was confirmed that it should be a structure.

The present invention relates to a temperature detection mechanism, an electronic thermometer, and a deep thermometer that enable miniaturization and high-precision temperature measurement without aging by using a sensor in which gallium is closely attached, and is used for industrial purposes. Has the potential.

1 Temperature detection mechanism
2 Electronic thermometer
3 Temperature detection mechanism
4 Electronic thermometer
10 Temperature sensitive part
20 Sensor body
21 gallium layer
22 Protective layer
23 Control unit
23a Temperature output section
23b Melting point detector
23c Correction value correction part
23d Compensated temperature output unit
23e Temperature display
30 microcapsules
31 gallium layer

Claims (3)

In a temperature detection mechanism that uses gallium as a temperature standard and has a function of automatically calibrating the detected temperature when the detected temperature of the sensor passes through the melting point of gallium.
The sensor includes a sensor main body portion, a gallium layer that is in close contact with the periphery of the sensor main body portion, and a protective layer that covers the periphery of the gallium layer .
A temperature detection mechanism , wherein the gallium layer is composed of a resin layer in which microcapsules containing gallium are dispersed .
An electronic thermometer comprising the temperature detection mechanism according to claim 1 .
A deep thermometer including a heat flow compensation system using the temperature detection mechanism according to claim 1 .

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