JPH0627719B2 - Odor detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an odor detecting device capable of detecting various odors, that is, flavors, fragrances and odors, and displaying the intensity of the odor. is there.

[Conventional technology]

Conventionally, a sensor that uses liquid crystals as a sensor to measure odor.A device that ionizes air at a high voltage to read changes in ionic current.Uses an organic semiconductor such as .beta.-carotene. For measuring the EEG response of humans For using a bilayer membrane and a crystal oscillator For measuring the membrane potential of communis or gardenia mesophyll cells For using a thermistor and a membrane Using an oxide semiconductor What was there (Japanese Patent Laid-Open No. 54-1142
(See Japanese Patent Publication No. 96), and many others have been reported.

[Problems to be Solved by the Invention]

However, is poorly sensitive to ammonia, which is a foul odor, and has a slow response. In addition, is expensive and the device becomes large.

Other than that, there is a problem that organic substances are difficult to be put into practical use because they are apt to undergo oxidative deterioration and cannot withstand long-term use.

The present invention has been made to solve the above-mentioned problems, and an alcohol-selective gas sensor in which a tin oxide semiconductor carries an oxide of an alkaline earth metal can be used in addition to alcohols, ketones, aldehydes, organic acids and Various odors (flavors, fragrances and odors) that are thought to be caused by hydrogen sulfide, mercaptans, etc. in addition to esters
It has been found that the odor detection device exhibits high sensitivity to, and an odor detection device capable of easily detecting odor by using this sensor.

[Means for Solving the Problems]

The odor detecting device according to the present invention comprises an odor sensor including an alcohol-selective gas sensor in which a tin oxide semiconductor carries an oxide of a metal containing at least one of alkaline earth metals (Be, Mg, Ca, Sr, Ba). It has a detection part and an odor display part which displays the output of this odor detection part.

[Action]

In the present invention, since the sensor uses a tin oxide semiconductor carrying an oxide of a metal containing at least one alkaline earth metal, various odors can be detected with high sensitivity.

〔Example〕

FIG. 1 is a schematic diagram showing the structure of an embodiment of the present invention. In this figure, reference numeral 1 denotes a housing, which has a suction port 2 and an exhaust port 3, and a passage 4 is formed between the both. Reference numeral 5 is a suction pump, and 6 is a SnO ₂ —CaO sensor, which is provided in the passage 4 so that the inhaled odor touches. Reference numeral 7 denotes a measurement circuit, for example, a bridge circuit, which together with the sensor 6 provides an odor detector 8
Are configured. The odor display unit 9 digitally or analogically displays the intensity of the odor. Reference numeral 10 is a power supply, and a rectifier circuit or the like for obtaining an appropriate DC voltage from a battery or a commercial power supply is used.

Although FIG. 1 shows the case of the suction type odor detector, the present invention can be applied to the case of the diffusion type without using the suction pump 5. Further, the odor detection unit 8 and the odor display unit 9 may be separated from each other, instead of being close to each other. Further, the odor display unit 9 may have a peak hold function, a buzzer, a lamp display, or other various display functions.

FIG. 2A is a diagram showing an example of a support mechanism for the sensor 6 of the embodiment shown in FIG. In FIG. 2 (a), the sensor 6 is
It is attached to the support pin 62 by a heater wire 61. 63 is a socket and 64 is a power terminal.

FIG. 2 (b) shows a case of a sintered sphere type as the sensor 6, which is a sintered sphere in which a platinum wire 6a is a tin oxide semiconductor carrying an oxide of a metal containing at least one alkaline earth metal. It is covered with the semiconductor portion 6b.

FIG. 2 (c) shows a case where the sensor 6 is of a substrate type, in which electrodes 6d and 6e and a tin oxide semiconductor carry an oxide of a metal containing at least one alkaline earth metal on the substrate 6c. And a semiconductor portion 6f are formed, and electrodes 6d and 6e are formed.
6 g of platinum wire is attached to the.

The sensor 6 is not limited to the hot wire semiconductor sensor.

FIG. 3 shows an example of the circuit of the embodiment shown in FIG. In this figure, the sensor 6 constitutes a bridge circuit together with the resistors R ₀ , R ₁ and R ₂ . The same reference numerals as those in FIG. 1 denote the same parts.

Next, the operation of the embodiment shown in FIG. 1 will be described.

The suction pump 5 takes in the odor in the outside air at a suction speed of about 500 m / min. The sensor 6 reduces the resistance value of the taken-in odor in proportion to its concentration, and the bridge circuit 7 outputs an output, which is displayed on the odor display unit 9.

Fig. 4 shows that coffee powder is enclosed in a container of constant volume,
A sensor 6 of _SnO 2 -CaO based on the vessel, conventional _SnO 2 -Pd system and a sensor (see JP-A-54-114296) was placed, and smell sensitivity when compared at room temperature It is a figure which shows the relationship with time. A curve A is according to the present invention, and a curve B is for the conventional example. The odor sensitivity is standardized.

As can be seen from this figure, the odor detecting device of the present invention can detect odor with high sensitivity.

Next, the sensor 6 used in the present invention will be described in detail.

In the above embodiment, the sensor 6 is SnO ₂ −.
A CaO-based hot-wire semiconductor type sensor was used, which is generally SnO ₂ with alkaline earth metal (Be, Mg,
Any material that supports an oxide of a metal containing at least one of Ca, Sr, and Ba) may be used. Such a sensor is conventionally used as an alcohol-selective sensor (see Japanese Patent Laid-Open No. 62-847).

An example of a method of manufacturing the sensor 6 will be described below.

Sn (OH) ₄ obtained by dropping ammonia water into an aqueous solution of high-purity SnC ₄ was dried, pulverized, and then calcined at 700 ° C. for 8 hours to obtain SnO ₂ . Note that a small amount of Sb ₂ O ₃ was added to obtain an appropriate resistance value. This SnO ₂ was finely pulverized and dispersed in water to form a paste, which was spherically coated so as to cover the noble metal wire coil that also serves as the output detection electrode of the gas sensor and the heater. After drying, a predetermined current was applied to the coil. heated by sintering SnO _2, to obtain a heat ray type semiconductor gas sensor composed mainly of SnO _2. Then, Ca (NO ₃ ) ₂
Carrying 0.5mo / aqueous solution of CaO as CaO 4m
After impregnating the sintered body of SnO ₂ so as to be 0% and drying,
The sensor 6 was obtained by firing at 600 ° C. for 30 minutes.

The present invention can detect not only the above-mentioned scent of coffee but also other odors such as soap, marcaptan, and yuzu.

Fig. 5 is a sensitivity curve showing the results of detecting the scent of soap.
It is similar to FIG. Similarly, FIG. 6 is a sensitivity curve in the case of mercaptan and FIG. 7 is a case of Yuzu.
Shows the case of a conventional odor detection device using a SnO ₂ -Pd based sensor.

It can be seen that the odor detection sensitivity of the odor detection device of the present invention is extremely high in any of the cases shown in FIGS.

The present invention can also detect a bad odor with high sensitivity.

〔The invention's effect〕

As described above, the present invention uses the sensor in which the oxide of the metal containing at least one of the alkaline earth metals is carried on the SnO ₂ semiconductor to form the odor detecting portion, and outputs this output to the odor display portion. Since the display is made possible, it is possible to quantitatively compare various odors conventionally discriminated by the human sense of smell, and since the sensor is a semiconductor, the power consumption is extremely small and it is suitable as a portable type. Moreover, it is also useful as a detector because it can sensitively detect the odor of minute spaces.

[Brief description of drawings]

FIG. 1 is a schematic configuration view showing an embodiment of the present invention, FIG. 2 (a) is a view showing an example of a sensor support mechanism of the embodiment of FIG. 1, and FIG. 2 (b) is a sintered ball type. FIG. 2 (c) is a plan view showing a substrate type sensor, FIG. 3 is a circuit diagram of the embodiment shown in FIG. 1, and FIG.
The figure shows the odor sensitivity curve diagram for coffee aroma showing the measurement results of the conventional example and the present invention, and FIGS. 5, 6, and 7 show the aroma of soap, mercaptan and yuzu, respectively. It is an odor sensitivity curve figure. In the figure, 1 is a housing, 2 is a suction port, 3 is an exhaust port, 4 is a passage,
5 is a suction pump, 6 is a sensor, 7 is a measuring circuit, 8 is an odor detector, and 9 is an odor display.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-60349 (JP, A) JP-A-62-847 (JP, A) JP-A-63-45552 (JP, A) JP-A-63- 40846 (JP, A)

Claims (1)

[Claims] 1. A tin oxide semiconductor containing an alkaline earth metal (B
e, Mg, Ca, Sr, Ba) having an odor detection part equipped with a sensor carrying a metal oxide containing at least one of odor detection part and an odor detection part for displaying the output of this odor detection part. Characteristic odor detection device.