JP2001318069A - Expired gas analytical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and highly accurate semiconductor type expired gas analytical device. SOLUTION: This analytical device is equipped with a suction means 1 of expired gas, a suction tube 2, a semiconductor type gas sensor element 3, a means 4 for operating the semiconductor type gas sensor element an operation means 5 for taking out an output signal, and a display means 6 for displaying an output signal level based on the output signal from the semiconductor type gas sensor element. The small and highly accurate analytical device seldom influenced by interfering gas in the expired gas is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a breath gas analyzer for detecting trace gas components contained in breath, especially acetone, and to a small and inexpensive breath gas analyzer which can be easily used in ordinary households. It is. Acetone is a kind of ketone body, a metabolite of fatty acid subjected to β oxidation, known as a useful index of metabolism such as whether energy metabolism is not biased to fatty acids, and fat metabolism such as obesity, diabetes, lipid metabolism It is known to provide information relevant to monitoring.

[0002]

2. Description of the Related Art In recent years, attention has been focused on detecting trace gas components contained in exhaled breath from health information from the human body and applying the detection to information on a living body. This is because there is no pain as in the case of collecting blood, there is no fear of infection, and metabolic information of a living body can be grasped relatively easily. However, various gases contained in exhaled breath are extremely low in ppb level, and only about 100 types have been identified today, but it is said that they contain hundreds of components in total and are involved in other types. Therefore, in combination with the means for collecting and concentrating exhaled air, research has been conducted on a large-sized analyzer such as a gas mass. Mass spectrometers have not always been highly accurate, but have been used primarily because of the qualitative analysis of the gas, that is, the advantage of being able to identify the type of gas.

On the other hand, semiconductor gas sensors have the advantage of being small and inexpensive, but have problems in selectivity and sensitivity. For this purpose, they are applied to the detection of mercaptans and alcohol for the purpose of detecting bad breath and alcohol. However, there are few studies that have been studied for the purpose of other breath analysis.

[0004]

These conventional breath analyzers are, for example, in the case of a gas mass (gas chromium spectroscope), the analyzer itself is large and expensive, and the analysis requires a high level of specialized knowledge. Need. In addition, since the sensitivity is low, it is necessary to use some kind of concentration technique in combination. In any case, gas mass cannot be used in ordinary households.

Among the small and inexpensive methods for analyzing expired gas, there are physical sensors such as infrared rays. However, in the case of infrared rays, the cell length is long due to the low concentration of the target gas, which is not practical. Because there is not, use of a chemical sensor is conceivable basically.

Regarding chemical sensors, among various chemical sensors, a semiconductor gas sensor is a gas sensor having high sensitivity because it utilizes a relatively sensitive characteristic of generating conductivity by reduction of surface oxygen by a reducing gas. There is, however, the first challenge is poor sensitivity. Since the concentration of gas in exhaled gas is at the ppb level, there is a problem that good sensitivity cannot be obtained.

[0007] The second problem is selectivity. The semiconductor gas sensor has a characteristic of indiscriminately detecting a reducing gas even if there is a slight difference in sensitivity. In particular, in the case of exhalation, it is extremely difficult to target and detect the target acetone without any influence of coexisting water vapor or other trace organic gas.

The above two are major problems when the semiconductor gas sensor is applied to breath analysis.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a breathing and breathing suction means, a suction tube, a semiconductor gas sensor element, and the operation and output signals of the semiconductor gas sensor element. It is provided with a calculating means for taking out and a display means for displaying an output signal level based on an output signal from the semiconductor gas sensor element. The breathing gas is continuously collected through the tube by the suction means, the semiconductor gas sensor element is operated, and the output signal is displayed, so that the concentration of the organic gas (acetone) in the breath can be easily grasped with a compact device. be able to. In addition to the above, there is a configuration of the apparatus in which there is no breathing and breathing suction means and no suction tube. In this case, naturally, the subject needs to perform an operation of blowing his / her breath on the semiconductor gas sensor element.

In particular, for a semiconductor sensor element, a pair of comb-shaped electrodes is provided on an insulating base material provided with a heating means, and the surface of the comb-shaped electrode is selected from the group consisting of tin oxide, indium oxide, and zinc oxide. A porous coating containing at least one compound selected from the group consisting of tungsten, molybdenum and chromium and at least one element selected from the group consisting of palladium, platinum and rhodium I do.

The present semiconductor sensor element includes tin oxide,
One or more compounds selected from the group consisting of indium oxide and zinc oxide adsorb oxygen molecules, but do not adsorb organic compounds such as acetone. On the other hand, one or more oxides selected from the group of tungsten, molybdenum and chromium
Many organic compounds are adsorbed on the surface. In particular, by using these elements in combination with one or more noble metal elements selected from the group consisting of palladium, platinum, and rhodium, effective molecular adsorption can be achieved without dissociating or oxidizing specific organic gases. Can be performed. As a result, the molecularly adsorbed organic gas desorbs well depending on the temperature of the semiconductor sensor element, and at least one compound selected from the group consisting of tin oxide, indium oxide, and zinc oxide adsorbs in a concentrated form. Reacts with oxygen. At least one compound selected from the group consisting of tin oxide, indium oxide, and zinc oxide captures electrons in the band of the semiconductor by the adsorbed oxygen, so that the trapping is lost and conductivity is generated. Therefore, the organic gas is detected by a change in resistance (reduction in resistance) of the semiconductor sensor element.

In the device of the present invention, high-temperature operation is set by a heating means attached to the device, and at least one compound selected from the group consisting of tin oxide, indium oxide and zinc oxide is oxidized and in an insulated state. . Organic gas (acetone)
Even in the presence of acetone, it operates in this state, and is completely oxidized by one or more oxides selected from the group of tungsten, molybdenum and chromium and one or more noble metal elements selected from the group of palladium, platinum and rhodium . Next, when the temperature of the heating means is lowered, acetone is weakly and effectively adsorbed for the above-mentioned reason, and is concentrated in a bulk of one or more compounds selected from the group of tin oxide, indium oxide, and zinc oxide. Spill over. As a result, a change in resistance occurs, and acetone is detected from the decrease in resistance. Since the catalyst is effectively concentrated on the surface of the catalyst material and flows into the bulk, effective detection sensitivity can be obtained even with a low concentration of acetone. The combination of material composition and operating temperature provides a beneficial selectivity for special organic gases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is directed to a suction means for breathing and exhalation, a suction tube, a semiconductor gas sensor element, means for operating the semiconductor gas sensor element, and an operation for extracting an output signal. Means and display means for displaying an output signal level based on an output signal from the semiconductor gas sensor element.

The exhaled breath is effectively sucked through the suction tube by the suction means and reaches the semiconductor gas sensor element. The semiconductor gas sensor element periodically repeats a high-temperature operation and a low-temperature operation cycle by means for operating the semiconductor gas sensor element. When a small amount of acetone gas to be detected is contained in the exhaled breath, the concentration is detected by the semiconductor gas sensor element during the low-temperature operation, and the resistance value of the sensitive portion of the semiconductor gas sensor element decreases. Since the change in the resistance value is related to the concentration of the acetone gas, the change in the resistance value is converted into, for example, a voltage, amplified, and compared with a target value, whereby the concentration level of the acetone gas can be output. By displaying this output signal level on a display device, it is possible to know what density level was. As the display device, any device such as an LED, a neon tube, and a liquid crystal can be used. Thus, the state of fat metabolism of the human body can be determined with a simple device without causing any pain or risk of infection. Obesity is evaluated with a weight scale or body fat scale, but by directly knowing the acetone concentration involved in fat metabolism,
Diabetes prevention can be done.

A second embodiment of the present invention is based on a semiconductor gas sensor element, means for operating the semiconductor gas sensor element, arithmetic means for extracting an output signal, and an output signal from the semiconductor gas sensor element. A display means for displaying the output signal level is provided. In this case, an operation is required in which a person blows his / her breath on the semiconductor gas sensor element. The operation after breathing is the same as that in the first embodiment.

According to a third embodiment of the present invention, a pair of comb-shaped electrodes are provided on an insulating base material provided with a heating means as a semiconductor gas sensor element, and tin oxide is provided on the surface of the comb-shaped electrodes.
At least one compound selected from the group consisting of indium oxide and zinc oxide and at least one oxide selected from the group consisting of tungsten, molybdenum and chromium and at least one compound selected from the group consisting of palladium, platinum and rhodium It is configured using an element formed with a porous coating containing an element. Due to the effect on the material composition, the porous coating of the present configuration has an effective detection capability for acetone. The heating means on the back surface allows the porous coating to change its temperature periodically. By sensing the change in the resistance value of the porous film between the comb-shaped electrodes during low-temperature operation, it is possible to detect a small amount of acetone present in the exhaled breath.

According to a fourth embodiment of the present invention, the substrate of the semiconductor type gas sensor element has a center line surface roughness of 0.5.
It is configured using a base material of μm or more. This is because a film formed by thick film printing with a film thickness of 5 to 15 μm is used as the film of the semiconductor gas sensor element. This is because, in the case of thin film forming means such as sputtering, the film is too thin, has high impedance, and is difficult to handle in a controlled manner.
In this case, the porosity of the porous film formed by the thick film printing is affected by the surface roughness of the substrate, and the surface roughness is 0.5%.
This is because the use of a substrate having a size of μm or more is advantageous in sensitivity. In the case of a normal ceramic substrate, the center line surface roughness is 0.1 μm or less in terms of surface roughness. However, by using the substrate having this configuration, higher sensitivity can be expected.

In a fifth embodiment of the present invention, the base material of the semiconductor gas sensor element has an average pore diameter of 0.2 μm.
It is configured using a gas-permeable base material selected from the following group of alumina or zirconia. Average pore size is 0.2μm
Since a comb-shaped electrode and a semiconductor oxide film are formed on the surface of the air-permeable substrate selected from the following group of alumina or zirconia, the semiconductor oxide film itself becomes extremely porous. Further, since the gas to be detected diffuses from the back surface of the substrate and comes into contact with the gas-sensitive film of the semiconductor oxide, the semiconductor oxide film becomes extremely active, and high-sensitivity gas detection is expected.

In a sixth embodiment of the present invention, the semiconductor gas sensor element has an average pore diameter of 0.2 μm
Using a gas-permeable base material selected from the group of alumina or zirconia below, and using a gas-permeable base material whose surface is coated with one or more oxides selected from the group of zirconia or silica I do. In addition to the effects of the fifth embodiment, the surface of the air-permeable substrate is coated with one or more oxides selected from the group of zirconia or silica, so that the substrate is particularly It is resistant to water vapor and acidic gases such as sulfur dioxide and nitrogen dioxide, and is less susceptible to the effects of interfering components in exhaled breath and gases that coexist with general atmosphere. The expired gas analyzer configured as described above has extremely high reliability and stable characteristics, which is advantageous.

In a seventh embodiment of the present invention, a pair of comb-shaped electrodes are provided on an insulating base material provided with a heating means as the semiconductor gas sensor element, and tin oxide and indium oxide are provided on the surface of the comb-shaped electrodes. , One or more compounds selected from the group of zinc oxide, one or more oxides selected from the group of tungsten, molybdenum, and chromium, and one or more elements selected from the group of palladium, platinum, and rhodium. And a second porous film formed on zeolite and supporting tungsten oxide and palladium on the surface thereof. The heating means heats the semiconductor gas sensor element periodically between a high temperature state for refreshing and a low temperature state for detection. The second coating can control the gas adsorption by the molecular sieving effect of the pores of zeolite molecules.In addition, tungsten oxide and palladium have the ability to condense acetone because they have good acetone adsorption characteristics. . Acetone concentrated in the second coat is tin oxide in the first coat,
At least one compound selected from the group consisting of indium oxide and zinc oxide and at least one oxide selected from the group consisting of tungsten, molybdenum and chromium and at least one compound selected from the group consisting of palladium, platinum and rhodium Since it contains elements, it reduces the adsorbed oxygen of one or more compounds selected from the group consisting of tin oxide, indium oxide, and zinc oxide as the base, increases conductivity, and increases the concentration due to the relationship between the resistance acetone concentration characteristics of the film and the concentration. Detection becomes possible. The expired gas analyzer configured as described above has extremely high reliability and stable characteristics, which is advantageous.

[0021]

FIG. 1 to FIG. 8 show an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a schematic diagram of an expired gas analyzer according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a suction unit. Various types of pumps correspond to this. 2
Is a suction tube. The second suction tube connects a portion for collecting exhaled gas by the first suction means and a measurement system for exhaled gas. Reference numeral 3 denotes a semiconductor gas sensor element, and the semiconductor gas sensor element 3 includes four operation means, five calculation means, and six display devices of the semiconductor element. Although not essential to the analyzer, the measurement system may include a separate bypass system and a flow path switching valve 7 from the viewpoint of effective sampling of exhaled gas. As described in FIG.
Since the initial amount of exhaled breath differs from the exact expiratory concentration, it may be collected by switching the flow path with a valve.
In particular, even if the bypass flow path is not provided as shown in FIG. 1, the expiration gas may be analyzed at a short timing by the three semiconductor gas sensor elements and the maximum value thereof may be collected. Examples of the form of the semiconductor gas sensor element 3 include a gas-functional film formed by forming a comb-shaped electrode using gold, platinum or the like on a substrate such as alumina provided with a heating means, and generally a hot-wire semiconductor. Any one of the platinum coil wires having a gas functional coating formed on a platinum coil wire which also serves as a heating means, which is referred to as a heating means, may be used. The above element is housed in a mesh metal case provided with an explosion-proof structure, and is used by connecting a lead wire to a pin for taking out the input power and signal output of the heating means. Whichever type of configuration is used, periodic operation of setting the low-temperature temperature and setting the high-temperature temperature is required. In a semiconductor device, oxygen traps conductive electrons in a high temperature state, is in a high resistance state, comes into contact with a target reducing gas, and has a low sensitivity at a low temperature where sensitivity is high. The gas concentration is detected from the gas concentration and the resistance characteristic of the gas to be detected on the low-temperature operation side. Appropriate timing such as means for periodically controlling the temperature of the heating means of the semiconductor sensor element and the last fixed time of the low-temperature operation is determined, and the resistance value is measured. Instead of measuring the resistance value, the operation means 4 of the semiconductor element is responsible for measuring the voltage at a constant current. In addition, the microcomputer mainly performs operations such as specifying a data sampling time using a microcomputer or calculating a gas concentration from a series of data values by using a relationship of a gas concentration resistance value characteristic that is pre-stored. Are the arithmetic means 5 of the semiconductor sensor element.
The gas concentration resistance characteristics to be remembered can also be set including the contents for correcting the correlation with the analysis value from blood. Displaying the measured values in digital or analog quantities is performed by the display means 6 of the semiconductor sensor element. As the display means 6, an LED, a fluorescent display tube, a liquid crystal, or the like is used. The exhaled gas is passed through the suction tube 2 to the place where the semiconductor sensor element is provided by the one suction means, where the gas concentration is analyzed by the series of operations described above, and the measurement level is reduced. Is displayed. In addition, although not shown in FIG. 1, according to the type of the detection gas, a tube with little adsorption, for example, a fluorine resin, is used, and at the same time, a heating means such as a heater is externally provided to avoid condensation of moisture and the like. You may have. From the above,
Unlike blood collection, various physiological information of the human body can be grasped without pain. Also, in FIG. 1, the size of the entire system is unknown, but overall, the entire analyzer can be configured extremely compact, and it is required to frequently measure by linking to a diet or the like. Even with acetone,
It has advantages such as portability.

(Embodiment 2) FIG. 2 is a schematic diagram of an expired gas analyzer according to Embodiment 2 of the present invention. FIG. 3 is a block diagram of a semiconductor gas sensor element unit of the breath gas analyzer.
In FIG. 2, reference numeral 8 denotes a main body of the expired gas analyzer.
The breath gas analyzer has nine semiconductor gas sensor elements and one
Display devices indicated by 0 and 11 are mounted. The display device 10 displays a gas concentration analysis value on a liquid crystal display 10 using a liquid crystal, and displays a gas concentration level using an LED 11.
The semiconductor gas sensor element of the ninth embodiment has the same configuration as that of the third embodiment. In this embodiment, unlike the previous embodiment, a person directly blows on the semiconductor-type gas sensor element to analyze the breath concentration. In FIG. 3, reference numeral 9 denotes a semiconductor gas sensor element;
Is a display means, and 14 is an operation means. These functions are
This is the same as the case described in the first embodiment. 12, 13, 1
Reference numeral 4 denotes a control circuit, which is housed in the main body of the expired gas analyzer of FIG. The people,
The operation until the measured value is displayed until the breath is blown on the semiconductor gas sensor element is the same as in the above-mentioned 1. Since the breath gas analyzer is small and portable, it is convenient to carry it for the purpose of frequently detecting the acetone concentration as monitoring of the fat metabolic state of the human body.

(Embodiment 3) FIG. 4 shows a conceptual diagram of a cross section of a semiconductor gas sensor element according to Embodiment 3 of the present invention. In FIG. 4, reference numeral 15 denotes an insulating substrate provided with a heating unit. The semiconductor gas sensor element is composed of a comb-shaped electrode 16, which is further laminated on 15 insulating base materials, and one or more compounds 17 selected from the group consisting of tin oxide, indium oxide, and zinc oxide, and tungsten, molybdenum, and chromium. A porous coating containing at least one oxide selected from the group and at least one element selected from the group consisting of palladium, platinum and rhodium is provided. Since the coating is fired at a much lower temperature than the sintering takes place, the coating becomes porous. The porosity can be further increased by reducing the particle size of the compound to be compounded or by adding an organic substance which is completely lost during firing. Among the components forming a gas-functional coating,
At least one compound selected from the group consisting of tin oxide, indium oxide, and zinc oxide has properties as an n-type semiconductor oxide. These alone have basically some sensitivity to reducing organic gas. One or more oxides selected from the group of 18 tungsten, molybdenum, and chromium provide an effective increase in sensitivity, especially to acetone. This is a finding found as a result of a preliminary test of sensitivity evaluation for acetone. The reason why the sensitivity is improved is unknown, but among the transition metal elements,
This is probably because it has an electronic structure effective for adsorbing acetone. The effective addition range of one or more oxides selected from the group consisting of tungsten, molybdenum and chromium to one or more compounds selected from the group consisting of tin oxide, indium oxide and zinc oxide used as a base is 1% by weight. The degree was effective, and the range of 5% to 20% by weight was effective. One or more elements selected from the group consisting of 19 platinum, rhodium and palladium are further effective in improving the sensitivity of acetone. This is presumed to be because these white metal elements adsorb acetone and exert an effect of relatively easily causing the spillover to the adsorbed oxygen site of the n-type semiconductor oxide. The addition amount of these white metal elements is effective from 0.05% by weight, and the effect is saturated at about 0.5% by weight. With the above configuration, sensitivity of two orders of magnitude, that is, 100 times or more, is obtained with respect to low-concentration acetone of 0.1 PPM level required for analysis in breath. This is sufficiently accurate for practical use.

An alumina substrate having dimensions of 2 mm × 5 mm × 0.5 mm and a center line surface roughness of about 1.2 μm was used, and a platinum resistance pattern having a resistance value of about 10Ω was formed on one side of each side. On the other surface, a comb electrode was formed. The gas functional substance was produced by the following method. Disperse 50 parts by weight of indium oxide, 20 parts by weight of tungsten oxide, 0.1 parts by weight of platinum powder, 0.5 parts by weight of methylated cellulose, and 0.5 parts by weight of glass powder together with a solvent with a three roll. Then, a paste was prepared. The paste is applied on a comb-shaped electrode at a dry film thickness of about 10 μm, at 600 ° C.
Then, baking was performed to produce a sensitive film. In the performance test, acetone was humidified to 80% in a state where this element was placed in a reaction tube, a voltage was applied to the heater, and the sensor resistance was measured by a digital multimeter using a four-terminal method. It was sent in a state of containing 0.1 ppm in the air, and the characteristics were evaluated. After the temperature of the sensor element is increased to 450 ° C., the temperature is decreased to 180 ° C.
The resistance value in an equilibrium state at 180 ° C. was evaluated. The resistance in air containing no acetone was about 1.5 MΩ, but the resistance when passing 0.1 ppm of acetone was 1 MΩ.
The sensitivity was extremely high at 2 KΩ. In the case where one or more oxides and white metal elements selected from the group consisting of molybdenum oxide, tungsten oxide and chromium oxide were not contained, the sensitivity was not doubled in any case. As described above, it was confirmed that good characteristics were obtained with an extremely simple configuration.

(Example 4) FIG. 5 shows the sensitivity to 0.1 ppm of acetone when the center line surface roughness of the base material was changed according to an example of the present invention (that is, the air resistance value of acetone-containing air was changed). 4 shows a graph in which the relationship with a value obtained by dividing by a resistance value is evaluated. FIG. 5 shows zinc oxide 5 as a gas functional substance.
0 parts by weight, 15 parts by weight of molybdenum oxide, and 0.3 parts by weight of platinum were evaluated. As is clear from FIG. 5, a high sensitivity of two digits or more is obtained under the condition that the center line surface roughness of the substrate exceeds 0.5 μm. High sensitivity is achieved because the surface roughness of the base material increases and the porosity of the semiconductor oxide composition-based gas sensitive material increases,
This is presumed to be in a favorable state with respect to the diffusion of acetone into the pores.

(Embodiment 5) FIG. 6 is a conceptual view of a cross section of a main part of a semiconductor sensor element according to Embodiment 5 of the present invention. In FIG. 6, reference numeral 20 denotes a porous substrate selected from the group of alumina or zirconia having an average pore diameter of 0.2 μm or less. Alumina base material is excellent in insulation and strength including heat shock, and zirconia is excellent in water resistance and lacks affinity for organic gas.

On the surface of the porous substrate 20, a comb-shaped electrode 21 and a gas-functional coating 22 of a semiconductor oxide composition are formed. Since the substrate is porous, the gas to be detected also diffuses and reaches from the back surface of the substrate. At this time, diffusion of gas molecules can be controlled to some extent by the level of the average pore diameter. When the pore diameter is larger than 0.2 μm,
The strength of the base material is reduced, making it difficult to handle, and the gas molecule permeability cannot be controlled. When the average pore diameter is 0.2 μm or less, a certain difference in gas permeation rate occurs. Desirably, if the temperature can be controlled to 100 ° or less, the gas permeation rate can be favorably controlled by the difference between the molecular weight and the reactivity. This allows
The selectivity of acetone detection can be controlled. Acetone has been described as an example, but the same applies to other organic gases.

(Embodiment 6) FIG. 7 shows a conceptual diagram of a cross section of a main part of a semiconductor gas sensor element according to Embodiment 6 of the present invention. In FIG. 7, reference numeral 23 denotes a porous substrate selected from alumina or zirconia having an average pore diameter of 0.2 μm or less described in Example 6. The porous substrate 23 has air circulation holes extending from the front surface to the back surface. One or more films 24 selected from the group of zirconia and silica for the purpose of controlling the pores of the porous body are formed on the surface of the porous substrate 23 and used. Even if the sensitivity of gas detection is improved by using a porous substrate, it tends to cause capillary condensation in the pores and weaken to water vapor.Therefore, one or more types of films selected from the group of zirconia and silica By forming, the steam resistance can be improved. Since both zirconia and silica are hydrophobic and resistant to water, the removal of water vapor after sending a gas containing a large amount of water vapor, such as exhalation, is effectively performed, and the responsiveness of the resistance value recovery is improved. In addition, by controlling the pores using these films, the sensitivity of the device can be given selectivity to the gas type by utilizing the difference in the gas permeation speed.

(Embodiment 7) FIG. 8 is a sectional view of a main part of a semiconductor gas sensor element according to Embodiment 7 of the present invention. In FIG. 8, reference numeral 25 denotes an insulating substrate provided with a heating means, and a comb-shaped electrode 26 is further laminated on the insulating substrate 25 to form a first porous film 27 and a second porous film 28. I have. The first porous coating, tin oxide, indium oxide, one or more compounds selected from the group of zinc oxide and tungsten, molybdenum, one or more oxides selected from the group of chromium and platinum, palladium, Contains one or more elements selected from the group of rhodium. The second porous coating includes a zeolite supporting tungsten oxide and palladium oxide. The function of the first porous coating is as described in the previous examples. The second coating is formed for the purpose of further improving the selectivity to acetone. Water vapor and the like are adsorbed and removed by the zeolite, and gas such as alcohol is completely oxidized and removed by the tungsten oxide and the palladium oxide.

As a result, the selectivity to acetone gas is significantly improved. In particular, the second porous coating works effectively as a filter for exhaled gas. With the above configuration, the semiconductor gas sensor can detect the trace concentration of acetone in exhaled breath with a simple device and with high sensitivity with little influence of interfering gas.

[0032]

The exhaled gas analyzer of the present invention is implemented in the form described above, and has the following effects.

(1) Since the device is small and simple, and can be freely carried, the expiration gas can be analyzed on site at the required timing for both elderly and children without the pain of blood collection.

(2) In an environment in which various trace organic gases including water vapor coexist, there is little influence of interfering gas such as water vapor, and highly reliable breath gas analysis data of acetone can be obtained. .

(3) Highly sensitive data can be collected with desired frequency, especially for acetone gas, which is a measure of fat metabolism in the human body.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an expired gas analyzer according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a breath gas analyzer according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a main part of an expired gas analyzer according to a second embodiment of the present invention.

FIG. 4 is a conceptual sectional view of a semiconductor sensor element according to a third embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the substrate surface roughness and the acetone detection sensitivity of the semiconductor sensor element according to the example of the present invention.

FIG. 6 is a conceptual sectional view of a semiconductor sensor element according to a fifth embodiment of the present invention.

FIG. 7 is a conceptual sectional view of a main part of a semiconductor sensor element according to a sixth embodiment of the present invention.

FIG. 8 is a conceptual sectional view of a semiconductor sensor element according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction means 2 Suction tube 3 Semiconductor gas sensor element 4 Operating means of a semiconductor element 5 Same calculation means 6 Same display means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Niwa, Inventor 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Takahiro Umeda 1006 Kazuma, Kadoma, Osaka Prefecture F-term (reference) in Matsushita Electric Industrial Co., Ltd. FE49

Claims (7)

[Claims] 1. A suction means for breathing and exhalation, a suction tube, a semiconductor gas sensor element, a means for operating the semiconductor gas sensor element, an arithmetic means for extracting an output signal, and an output signal from the semiconductor gas sensor element. An exhaled gas analyzer comprising a display means for displaying an output signal level. 2. A semiconductor gas sensor element, means for operating the semiconductor gas sensor element, arithmetic means for extracting an output signal, and display means for displaying an output signal level based on the output signal from the semiconductor gas sensor element. Breath gas analyzer equipped. 3. A comb-shaped electrode is provided on an insulating substrate provided with a heating means, and at least one compound selected from the group consisting of tin oxide, indium oxide and zinc oxide is provided on the surface of the comb-shaped electrode. Uses a semiconductor gas sensor element formed with a porous coating containing one or more oxides selected from the group consisting of tungsten, molybdenum, and chromium and one or more elements selected from the group consisting of palladium, platinum, and rhodium. The expired gas analyzer according to claim 1 or 2, wherein: 4. The expiratory gas analyzer according to claim 1, wherein a substrate having a center line surface roughness of 0.5 μm or more is used as a substrate of the semiconductor type gas sensor element. 5. A gas-permeable substrate selected from the group consisting of alumina and zirconia having an average pore diameter of 0.2 μm or less as a substrate of a semiconductor gas sensor element.
3. The breath gas analyzer according to 2. 6. A gas-permeable base material having an average pore diameter of 0.2 μm or less selected from the group consisting of alumina and zirconia as the base material of the semiconductor gas sensor element, and the surface thereof is selected from the group consisting of zirconia and silica. 3. The expired gas analyzer according to claim 1, wherein a breathable base material coated with at least one oxide is used. 7. A comb-shaped electrode is provided on an insulating substrate provided with a heating means, and at least one compound selected from the group consisting of tin oxide, indium oxide and zinc oxide is provided on the surface of the comb-shaped electrode. A first porous coating containing at least one oxide selected from the group consisting of tungsten, molybdenum and chromium and at least one element selected from the group consisting of palladium, platinum and rhodium, and a zeolite on the surface thereof; 3. The expiratory gas analyzer according to claim 1, wherein a semiconductor gas sensor element formed with a second porous film supporting tungsten oxide and palladium oxide is used.