JPH1078404A - Odor sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect at least two kinds of gases and improve detection precision of odor constituted of a plurality of different gases by changing temperature of a single gas sensing body formed on a single substrate. SOLUTION: In a case where, for instance, two kinds of gases, ammonia and hydrogen, much more contained as compared with other gases as a gas to be detected (index gas) are detected, in regard to a sensor a sensor a sensing body 2 composed of SnO2 adding Pd and its electrodes 3, 3 are formed on one face of an alumina substrate of thickness of 0.2mm and size of 1×1, and a gas sensing body heater 4 composed of aluminum oxide and its electrodes 5, 5 are formed on the other face. This sensor shows a high sensitivity for ammonia at 300 deg.C and hydrogen at 450 deg.C. The sensitivity characteristic is utilized and two kinds of gases can be alternatively detected by one sensor by alternatively changing operation temperature, for instance, from 300 deg.C and 5 seconds to 450 deg.C and 5 seconds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to air conditioning, food processing,
In food storage and other various fields, it relates to odor sensors for detecting various odors used as indicators of air quality, quality, freshness, etc. for the purpose of air quality control, quality control, freshness control, etc. TECHNICAL FIELD The present invention relates to a heating type odor sensor using an object semiconductor as a gas sensitive body.

[0002]

2. Description of the Related Art An odor sensor used for the purpose of air quality control, quality control, freshness control, etc. is of a type which detects one kind of gas serving as an index of the odor among the gases constituting the odor, that is, a gas. Many types have selectivity. Therefore, use a sensitizer that selectively detects the target index gas, provide a special filter so as not to detect any other than the index gas, or use the signal processing to process other than the index gas if it has sensitivity to multiple gases. Various measures are taken, such as removing the influence of gas.

[0003]

In general, it is difficult to provide complete selectivity to an odor sensor, and it is almost impossible to completely eliminate the influence of miscellaneous gases. Therefore, it is extremely difficult to accurately specify various odors. In the case where there is sensitivity to a plurality of different gases under the same operating conditions, even if the sensitivity is low, a large sensor output is obtained when the gas concentration is high, so that an erroneous determination may occur. In particular, when the odor to be detected is composed of a plurality of gases, the possibility increases, and the detection accuracy is reduced and erroneous determination is inevitable. In addition, when the same gas as the gas to be detected is contained, there is a high probability that the same gas will be detected even with a different odor, resulting in an erroneous determination. An object of the present invention is to provide a highly reliable odor sensor by suppressing such a decrease in detection accuracy and the probability of erroneous determination.

[0004]

SUMMARY OF THE INVENTION An odor sensor according to the present invention is provided by changing the temperature of a single gas sensitive body formed on a single substrate, or by changing a plurality of gas sensors formed on a single substrate. By setting the sensitizers to different temperatures, at least two types of gases are detected, and the detection accuracy of an odor composed of a plurality of different gases is further improved.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An odor sensor according to the present invention is a sensor for detecting an odor composed of a plurality of different gases, and comprises a single gas sensitive body and a single gas formed on a single substrate. A heater for heating the gas-sensitive body, and by changing the temperature of the gas-sensitive body by adjusting the capability of the heater for heating the gas-sensitive body, detects two or more kinds of gases out of a plurality of different gases and smells. Is specified.

Further, the odor sensor of the present invention has a plurality of gas sensitizers formed on a single substrate and a single heater for heating the gas sensitizer, and is provided on the surface of the substrate on which the gas sensitizer is formed. By setting a temperature gradient along each of the gas sensitizers to different temperatures, two out of a plurality of different gases can be set.
It detects gas of more than species and specifies the smell.
Further, the odor sensor of the present invention has a plurality of gas sensitizers formed on a single substrate and a heater for heating the gas sensitizer provided for each gas sensitizer. By setting to, two or more kinds of gases out of a plurality of different gases are detected to specify the odor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail below, taking as an example the case where tobacco odor is detected. << Example 1 >> Various gases are contained in the tobacco smell.
Representative gases include ammonia, acetaldehyde,
There are formaldehyde, acetone, carbon monoxide, hydrogen, nitrogen oxides, etc., and it ranges from odorous components to odorless components. These gases are so small that they are susceptible to interference by various gases from other sources. This makes it difficult to identify the tobacco odor by detecting a specific type of gas. In the present embodiment, two types of gases, ammonia and hydrogen, which are contained relatively more than other gases, are selected as detection target gases (index gases).

FIGS. 1 to 3 show the structure of an odor sensor according to this embodiment. In this sensor, a sensitive body 2 made of SnO ₂ to which Pd is added and its electrodes 3 and 3 are formed on one surface of an alumina substrate 1 having a thickness of 0.2 mm and a size of 1 × 1 mm. A heater for heating a gas sensitive body made of ruthenium oxide and its electrodes 5, 5 are formed. Sensitizer 2 has a thickness of 400 nm and a size of 0.3 × 0.3 mm
And the sensitive body electrode 3 made of platinum has a thickness of 1.5 μm.
m, and the electrode spacing is 0.1 mm. Further, the heater 4 for heating the gas sensitive body has a thickness of 10 μm and a size of 0.7 × 0.
The heater electrode 5 made of platinum has a thickness of 1.5 μm and an electrode interval of 0.6 mm. FIG. 4 shows the sensitivity characteristics of this sensor to ammonia and hydrogen. As shown, the sensor is sensitive to ammonia at 300 ° C. and sensitive to hydrogen at 450 ° C. Using this sensitivity characteristic, the operating temperature of the sensor is set to, for example, “300 ° C.
By alternately changing "5 seconds.fwdarw.450.degree. C. for 5 seconds", these two types of gases can be detected alternately by one sensor.

On the other hand, the hydrogen detecting sensor is 400 to 45
At 0 ° C, for example, it shows some sensitivity to methane, so if only a sensor that detects hydrogen is used, if the methane concentration is sufficiently high, it will detect methane originating from sources other than smoking, such as mold, microorganisms, building materials, etc. May be determined to be a cigarette smell. In addition, if only the sensor for detecting ammonia is used, it shows sensitivity to alcohols at around 300 ° C.
Also in this case, for example, an erroneous determination may be made by detecting alcohol caused by cooking, cosmetics, or the like. On the contrary,
Since the sensor according to the present invention detects both hydrogen and ammonia, it detects only hydrogen or only ammonia by appropriately setting the detection threshold concentration for hydrogen and ammonia in proportion to the concentration contained in tobacco odor. Compared to the method using a single sensor, the possibility of erroneous determination due to different odor sources can be reduced,
The specific probability of tobacco odor is greatly improved.

Embodiment 2 FIGS. 5 and 6 show different embodiments of the odor sensor according to the present invention. This sensor has two sensitive layers of SnO ₂ doped with Pd and having a thickness of 400 nm and a size of 0.2 × 0.3 mm on one surface of an alumina substrate 11 having a thickness of 0.2 mm and a size of 1 × 2 mm. Body 12a, 12b and a thickness 10 of ruthenium oxide
A heater 14 for heating the gas sensitive body having a size of 0.4 μm and a size of 0.4 × 0.7 mm is provided. 2 sets of sensitive body electrodes 13
Each of a and 13b is made of platinum, has a thickness of 1.5 μm, and an interval between the electrodes is 0.2 mm. Also, the heater electrode 15
Is made of platinum, has a thickness of 1.5 μm, and an electrode interval of 0.5 m.
m.

FIG. 7 shows a temperature profile along the surface of the sensor element on which the gas sensitive body is formed. In the present embodiment, the heater 14 facing the sensitive body 12a
Is about 500 ° C., the temperature of the end of the sensitive body 12a close to the heater 14 is about 450 ° C.
The temperature at the end of the sensitive body 12b close to a is about 300 ° C. By keeping the heater power constant under these setting conditions, hydrogen can be detected by the sensitive body 12a and ammonia can be detected by the sensitive body 12b. That is, two types of gas of hydrogen and ammonia can be simultaneously detected by one sensor. By using the sensor of the present embodiment, compared to the case of using a single sensor that detects only hydrogen or only ammonia as in the first embodiment,
The possibility of erroneous determination can be reduced, and the specific probability of tobacco odor is greatly improved.

<< Embodiment 3 >> FIGS. 8 to 10 show the structure of a sensor according to this embodiment. This sensor is 0.2m thick
m, a thickness of 400 made of SnO ₂ with Pd added to one surface of an alumina substrate 21 having a size of 1.5 × 2.5 mm.
nm, two sensitive bodies 22 of 0.3 × 0.3 mm in size
a, 22b and two pairs of electrodes 13 for the photosensitive body made of platinum
a and 13b, and two gas-sensitive body heating heaters 24a and 24b each having a thickness of 10 .mu.m and a size of 0.4.times.0.4 mm made of ruthenium oxide on the other surface;
A set of the heater electrodes 25a and 25b is provided. The two pairs of electrodes for the sensing element are made of platinum, have a thickness of 1.5 μm, and the interval between the electrodes is 0.15 mm.
The two heater electrodes are made of platinum and have a thickness of 1.
At 5 μm, each electrode spacing is 0.25 mm.

In this embodiment, the power of each heater is adjusted to heat the sensitive body 22a to 450.degree. C. by the heater 24a and the sensitive body 22b to 300.degree. C. by the heater 24b.
Figure 4 shows the sensitivity characteristics of this sensor to ammonia and hydrogen.
The hydrogen is detected by the sensitive body 22a, and the ammonia is detected by the sensitive body 22b. If this characteristic is used, these two types of gases can be simultaneously detected by one sensor as in the second embodiment. By using this sensor, the possibility of erroneous determination can be reduced as compared with the case of using a single sensor that detects only hydrogen or only ammonia as described above, and the specific probability of cigarette odor is greatly improved. I do.

In the above embodiment, the case where tobacco odor is detected has been described. However, the present invention can be similarly applied to the case where other odors are detected. The number of gases to be detected is not limited to two, and it is also effective to set the number to three or more in order to further improve the detection accuracy depending on the odor. Therefore, the number of sensitive bodies can be optimized accordingly. Further, in the example, the case where SnO ₂ to which Pd was added was used as the sensitive material was described. However, the present invention is not limited to this, and a more suitable sensitive material may be used according to the gas to be detected. it can. Other constituent materials having the same function can be used as long as they do not contradict the gist of the invention. Also, the arrangement of the sensitive body and the heater, and the dimensions and structure of the elements are not limited to the embodiment. Further, the operating temperature of the sensor can be appropriately set according to the type of the detection target gas.

[0015]

By using the odor sensor according to the present invention, the detection accuracy of odors composed of a plurality of different gases and the probability of erroneous determination can be suppressed low, and the odor detection accuracy can be further improved. .

[Brief description of the drawings]

FIG. 1 is a plan view of an odor sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II 'of FIG.

FIG. 3 is a rear view of the sensor.

FIG. 4 is a diagram showing sensitivity characteristics of the sensor to ammonia and hydrogen.

FIG. 5 is a plan view of an odor sensor according to another embodiment of the present invention.

FIG. 6 is a sectional view taken along line VI-VI ′ of FIG. 5;

FIG. 7 is a diagram showing a temperature profile of a gas sensitive body forming surface of the sensor.

FIG. 8 is a plan view of an odor sensor according to still another embodiment of the present invention.

9 is a sectional view taken along line IX-IX 'of FIG.

FIG. 10 is a rear view of the sensor.

[Explanation of symbols]

1, 11, 21 Substrate 2, 12a, 12b, 22a, 22b Sensitive body 3, 13a, 13b, 23a, 23b Sensitive body electrode 4, 14a, 14b, 24a, 24b Gas sensitive element heater 5, 15, 25a , 25b Electrode for heater

Claims (3)

[Claims] 1. A sensor for detecting an odor composed of a plurality of different gases, comprising: a single gas sensitive body formed on a single base; and a single gas sensitive body heating heater. An odor sensor characterized by detecting at least two kinds of gases and adjusting the temperature of the gas sensible body by adjusting the capability of the heater for heating the gas sensible body. 2. A sensor for detecting an odor composed of a plurality of different gases, comprising: a plurality of gas sensitizers formed on a single base; and a single gas sensitizer heating heater; By providing a temperature gradient along the surface of the substrate on which the gas sensitizer is formed and setting each gas sensitizer to a different temperature, at least two types of gases are detected and the odor is specified. Sensor. 3. A sensor for detecting an odor composed of a plurality of different gases, comprising a plurality of gas sensitizers formed on a single substrate and a heater for heating the gas sensitizer provided for each gas sensitizer. An odor sensor comprising: detecting at least two types of gases and setting an odor by setting each gas sensitive body to a different temperature.