JP2853622B2 - Gas measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas measuring apparatus for measuring an odor substance or the like in a gas using a quartz oscillator or a surface acoustic wave device, and in particular, it is possible to dramatically improve the sensitivity of an odor sensor. It relates to a gas measuring device.

[0002]

2. Description of the Related Art A conventional gas measuring apparatus forms a gas adsorption film on the surface of an AT-cut quartz crystal resonator or a surface acoustic wave device, and detects a change in mass of the film caused when an odor molecule is adsorbed on the gas adsorption film. The concentration of the odor is detected by detecting the change in the resonance frequency of the vibrator or the like.

[0003] As one example of such a conventional technique, for example,
“Japanese Patent Application No. 5-304940” related to the applicant's other application
There is.

In Japanese Patent Application No. 5-304940, a combination of polyvinyl chloride (hereinafter referred to as PVC), a plasticizer and a lipid, which are constituents of an adsorbing film for an odorant, is appropriately selected. More odor substances can be detected, and the odor substance to be detected can be selectively detected.

[0005]

However, in Japanese Patent Application No. 5-304940, the amount of the odor substance adsorbed on the adsorption film is determined to some extent by the combination of the odor substance adsorption film and the gas to be measured. There is a problem that it is difficult to dramatically improve the sensitivity. Therefore, an object of the present invention is to realize a gas measurement device capable of dramatically improving the sensitivity of an odor sensor.

[0006]

According to a first aspect of the present invention, there is provided a gas measuring method for detecting an odorous substance based on a change in resonance frequency due to adsorption of an odorous substance on a gas adsorption film. In the apparatus, a first cooler for cooling a gas to be measured, an odor sensor including a quartz oscillator or a surface acoustic wave element provided with the gas adsorption film, and a second cooling for cooling the odor sensor And a measuring circuit for measuring the concentration of the odorant based on the output of the odor sensor.

According to a second aspect of the present invention, in the first aspect of the present invention, a dehumidifier is provided before the first cooler for cooling the gas to be measured.

According to a third aspect of the present invention, in a gas measuring device for detecting an odorous substance based on a change in resonance frequency due to adsorption of an odorous substance to a gas adsorption film, a quartz oscillator or a surface acoustic wave element, And an odor sensor comprising a gas adsorption film formed of polyvinyl chloride and diisodecyl phthalate provided on the element or the surface acoustic wave element.

In a fourth aspect of the present invention, the first and second aspects of the present invention are provided.
Wherein a gas adsorption film composed of polyvinyl chloride and diisodecyl phthalate is used as the gas adsorption film.

[0010]

The sensitivity of the odor sensor can be dramatically improved by cooling the gas to be measured and the odor sensor when measuring the gas using the gas cooler and the sensor cell cooler. In addition, by providing a dehumidifier in front of the gas cooler, it becomes possible to prevent malfunction of the odor sensor due to dew condensation or the like accompanying cooling of the gas to be measured.

Further, the odor adsorbing film is made of PVC and DIDP.
With this configuration, it is possible to prevent a decrease in sensitivity due to storage or the like without impairing response characteristics.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of the gas measuring device according to the present invention. In FIG. 1, 1 is an intake port, 2 is a pump, 3 is a dehumidifier, 4 is a gas cooler, 5 is a sensor cell, 6 is an odor sensor such as a quartz oscillator type, 7 is a sensor cell cooler, 8 is a measurement circuit, 9 Is an exhaust port, and 100 is an output signal.

An intake port 1 is connected to an intake end of a pump 2,
The output gas of the pump 2 is supplied to the dehumidifier 3. Dehumidifier 3
Is supplied to the gas cooler 4, and the output gas of the gas cooler 4 is supplied to the sensor cell 5.

An odor sensor 6 is provided inside the sensor cell 5, and an output gas of the sensor cell 5 is connected to an exhaust port 9. Further, the sensor cell 5 is provided with a sensor cell cooler 7, and the output signal of the odor sensor 6 is connected to the measurement circuit 8 and output from the measurement circuit 8 as an output signal 100.

The operation of the embodiment shown in FIG. 1 will now be described with reference to FIG. FIG. 2 is a characteristic curve diagram showing the amount of adsorbed amyl acetate molecules on the PVC-blended lipid membrane with respect to temperature.

First, the pump 2 sucks the gas to be measured from the intake port 1 and introduces it into the dehumidifier 3. For example, a film type dehumidifier is used as the dehumidifier 3 to remove moisture contained in the introduced gas to be measured.

The measured gas output from the dehumidifier 3 is supplied to a gas cooler 4. The gas cooler 4 is configured by using, for example, a Peltier element or the like, and cools the temperature of the supplied gas to be measured to “0 degrees”.

On the other hand, the sensor cell 5 is also cooled to the same "0 degree" as the temperature of the gas to be measured by the sensor cell cooler 7 composed of a Peltier element or the like.
Is supplied. The gas to be measured is sequentially exhausted from the exhaust port 9.

The odor substance in the gas to be measured is adsorbed on the gas adsorption film of the odor sensor 6 provided in the sensor cell 5, and changes the resonance frequency of the odor sensor 6. The measurement circuit 8 detects this resonance frequency change and outputs it as an output signal 100 to the outside.

The gas measurement environment is usually performed at about room temperature. As can be seen from FIG. 2, when the temperature of the odor sensor 6 is lowered, the amount of odor substances (amyl acetate molecules) adsorbed on the odor sensor 6 (PVC blend film) is reduced. Increase.

For example, when the temperature of the odor sensor 6 is "0 degree", the amount of adsorption increases about 20 times as compared with the case where the temperature is "40 degree". In other words, the sensitivity of the odor sensor 6 is 20
About twice as much.

As a result, the sensitivity of the odor sensor 6 can be significantly improved by cooling the gas to be measured and the odor sensor 6 when measuring the gas using the gas cooler 4 and the sensor cell cooler 7. Become.

Further, by providing the dehumidifier 3 in front of the gas cooler 4, malfunction of the odor sensor 6 due to condensation or the like due to cooling of the gas to be measured can be prevented.

Further, by providing a temperature control circuit or the like to control the temperature of the gas to be measured and the temperature of the odor sensor 6 at a constant temperature, it becomes possible to eliminate the influence of the temperature drift of the odor sensor 6.

Further, the gas adsorption film of the conventional odor sensor 6 is constituted by combining PVC, lipid and plasticizer as described above. Here, those using dioctyl phthalate (hereinafter referred to as DOP) as a plasticizer have good response characteristics, but have a problem that the sensor sensitivity is reduced when stored at a high temperature or the like.

FIG. 3 shows that DOP and diisodecyl phthalate (hereinafter referred to as DIDP) were used as plasticizers and stored for 2 days at a temperature of “60 ° C.” and a humidity of “95% RH” immediately after the production of the odor sensor. 6 is a table showing sensitivity and response speed in the case.

As can be seen from FIG. 3, DID is used as a plasticizer.
When P is used, the response characteristic is “30” as compared with DOP.
In the same way as "less than 1 minute", the sensitivity decreases by "85%" when the plasticizer is DOP, whereas it decreases by "43%" when the plasticizer is DIDP. It turns out that it is enough.

As a result, by forming the odor adsorbing film using DIDP as a plasticizer, it is possible to reduce the rate of decrease in sensitivity due to storage or the like without impairing response characteristics.

Further, the above-mentioned “Japanese Patent Application No. 5-3049”
In “40”, “lipid” was essential as a component of the odor-adsorbing film, but according to subsequent experiments, “lipid” is not necessarily required.

Therefore, the odor absorbing film is made of PVC and DIDP.
With this configuration, it is possible to prevent a decrease in sensitivity due to storage or the like without impairing response characteristics.

Although the cooling temperature of the gas to be measured and the cooling temperature of the sensor cell 5 are set to "0 degrees", it is a matter of course that the present invention is not limited to this value.

The components of the odor adsorbing film are PVC.
And a plasticizer, and the plasticizer is not limited to DIDP.

[0033]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first aspect of the present invention, by measuring the gas to be measured and the odor sensor using the gas cooler and the sensor cell cooler, the sensitivity of the odor sensor can be dramatically improved. The device can be realized.

According to the second aspect of the present invention, by providing a dehumidifier in front of the gas cooler, malfunction of the odor sensor due to dew condensation or the like due to cooling of the gas to be measured can be prevented.

According to the third aspect of the present invention, the odor adsorbing film is made of PVC and DIDP,
It is possible to prevent a decrease in sensitivity without impairing response characteristics.

Further, according to the fourth aspect of the invention, by forming the odor adsorbing film with PVC and DIDP, it is possible to prevent a decrease in sensitivity without impairing the response characteristics and to cool the gas to be measured and the odor sensor. This makes it possible to dramatically improve the sensitivity of the odor sensor.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a gas measurement device according to the present invention.

FIG. 2 is a characteristic curve showing the amount of adsorbed amyl acetate molecules on a PVC blend lipid membrane versus temperature.

FIG. 3 is a table showing the sensitivity and response speed when DOP and DIDP are used as plasticizers and stored for 2 days under conditions of a temperature “60 ° C.” and a humidity “95% RH” immediately after the production of the odor sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intake port 2 Pump 3 Dehumidifier 4 Gas cooler 5 Sensor cell 6 Odor sensor 7 Sensor cell cooler 8 Measurement circuit 9 Exhaust port 100 Output signal

Claims (4)

(57) [Claims] 1. A gas measuring apparatus for detecting an odor substance based on a change in resonance frequency due to adsorption of an odor substance to a gas adsorption film, wherein: a first cooler for cooling a gas to be measured; An odor sensor comprising a quartz oscillator or a surface acoustic wave element provided; a second cooler for cooling the odor sensor; and a measurement circuit for measuring the concentration of the odor substance based on an output of the odor sensor. A gas measuring device comprising: 2. The gas measuring apparatus according to claim 1, wherein a dehumidifier is provided before the first cooler for cooling the gas to be measured. 3. A gas measuring device for detecting an odor substance based on a change in a resonance frequency due to adsorption of an odor substance on a gas adsorption film, comprising: a quartz oscillator or a surface acoustic wave element; A gas measuring device comprising: an odor sensor including a gas adsorption film formed of polyvinyl chloride and diisodecyl phthalate provided on an element. 4. The gas measuring device according to claim 1, wherein a gas adsorption film formed of polyvinyl chloride and diisodecyl phthalate is used as the gas adsorption film.