JP2001074679A - Odor measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an odor measuring apparatus which can calculate the odor index of an odor which is constituted of a plurality of kinds of odor components. SOLUTION: Three kinds of gases A, B, C which contain respectively different odor components are used. Points of intersection of sensor outputs [-log(Rs/ Rb)] of two oxide semiconductor sensors CH1, CH2 at the time when the respective gases are adjusted to three kinds of odor indexes regarding respective standard gases so as to be measured are plotted. Values of the three kinds of odor indexes are identical in the gas A, the gas B and the gas C. When plots of the identical odor indexes of the gas A, the gas B and the gas C are connected by lines, odor index lines (dashed lines) such as contour lines are formed. A sample gas for an odor which is constituted of an order component contained in the gas A, the gas B or the gas C and whose odor index is unknown is measured so as to be plotted on an odor map. Then, the odor index of the sample gas can be estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an odor measuring device provided with two or more gas sensors having different response characteristics. Such an odor measuring device is used to identify or identify an odor in fields such as deodorization, aroma, food management, and measurement of malodor.

[0002]

2. Description of the Related Art Regarding odor measurement, 22 types of odor control substances designated by the Environment Agency, such as methyl mercaptan and trimethylamine, are subject to official regulations (Notification No. 72 of the Environment Agency on September 8, 1993, Analytical Methods for Odor Control Substances Matrix / Revision) is specified, and the sampling method, concentration method and measurement method of sample gas are specified. For substances other than odor control substances, the three-point odor bag method is performed under the guidance of an odor judge. According to the method, 6 persons who are said to have normal olfaction and are said to be
Using more than one person, give each panelist one odor bag with odor-free air filled with sample gas and two odor-free odor bags with odor-free air sealed, and select one odor bag to determine that sample gas is injected. Then, the odor index is calculated by a predetermined formula based on the selection results of the panelists (see the Environment Agency Notification No. 63, September 13, 1995, method of calculating the odor index).

However, in the official method described above, the measuring method is different for each offensive odor control substances, the operation is complicated, and there is a problem that accurate values are difficult to obtain unless consigned to a specialist. Further, there is a drawback that the measurement is time-consuming and thus unsuitable for on-site measurement.
The three-point odor bag method is not convenient because six or more panelists have to be collected, and there is a concern that the panelers need to smell the bad smell and affect the human body. In order to solve such problems, an odor measuring device using a gas sensor has been proposed. One of them is an odor index meter XP-349S (manufactured by Shin-Cosmos Electric Co., Ltd.) which can easily perform odor measurement. Are on sale. This odor index meter is provided with one oxide semiconductor sensor utilizing a phenomenon in which the electrical resistance of the oxide semiconductor changes due to a redox reaction with a malodorous substance in the sample gas as a gas sensor.

[0004]

Since the above-mentioned odor index meter has only one gas sensor, a correlation with the odor index is obtained when an odor composed of one kind of odor component is targeted. However, when an odor composed of a plurality of types of odor components is targeted, it is impossible to associate the odor index with the odor index due to a difference in sensitivity of the gas sensor to the type of the odor component. Therefore, an object of the present invention is to provide an odor measuring device that can accurately calculate an odor index even if it is composed of a plurality of types of odor components.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an odor measuring device provided with two or more gas sensors having different response characteristics, wherein the odor index is changed for each of a plurality of standard gases having known odor indexes. A relational expression between the sensor outputs of the two or more gas sensors and the odor index is calculated based on the sensor outputs of the two or more gas sensors at the time of measurement, and the relational expression and two or more gas sensors at the time of measuring the sample gas And an arithmetic unit for calculating the odor index based on the sensor output of the first embodiment.

A plurality of standard gases whose odor indexes are known are measured by changing the odor index. The operation unit is
A relational expression between the sensor output and the odor index is calculated based on the sensor outputs of two or more gas sensors when the standard gas is measured. At the time of sample gas measurement, the odor index is calculated based on the relational expression, so that an accurate odor index can be calculated even for an odor composed of a plurality of types of odor components.

[0007]

FIG. 1 is a schematic structural view showing one embodiment.
A measurement gas container 1 containing a sample gas or a standard gas having a known odor index is provided. Oxygen required for operation of the oxide semiconductor sensor is also injected into the measurement gas container 1. The measurement gas container 1 is connected to the inlet side of the sensor cell 3 via the port P1 and the valve V1. A zero gas container 2 containing a zero gas made of clean air containing oxygen is provided. Zero gas container 2 is connected to port P
2 and the valve V2 are connected to the inlet side of the sensor cell 3. On the inlet side of the sensor cell 3, a valve V
Either the measurement gas container 1 or the zero gas container 2 is connected by opening / closing 1, V2. Six oxide semiconductor sensors having different response characteristics are arranged inside the sensor cell 3. The outlet side of the sensor cell 3 is a flow meter 4
Is connected to the suction side of the suction pump 5. The port P3 is connected to the discharge side of the pump 5.

The oxide semiconductor sensor of the sensor cell 3 includes:
A signal processing unit 6 for calculating a sensor output based on the amount of change in the resistance value (sensor resistance value) of the oxide semiconductor sensor is electrically connected. The signal processing unit 6 is connected to a personal computer (PC) 8 via a controller 7. The controller 7 is also electrically connected to the flow meter 4 and the pump 5. The controller 7 controls the operation of the pump 5 based on a flow signal from the flow meter 4. The calculation unit of the present invention is realized by the PC 8.

Next, the operation of this embodiment will be described. After the zero gas container 2 is connected to the port P2, the valve V2 is opened with the valve V1 closed, and the pump 5 is operated by the controller 7 to supply the zero gas to the sensor cell 3.
The channel system is cleaned. The zero gas supplied to the sensor cell 3 is supplied to the port P via the flow meter 4 and the pump 5.
It is discharged from 3. Then, the value when the sensor resistance value is stabilized is stored in the signal processing unit 6 as the base resistance value Rb.

After the measurement gas container 1 containing the sample gas or the standard gas is connected to the port P1, the supply of the zero gas is stopped by closing the valve V2, and the valve V1 is further opened to store the sample gas or the standard gas in the sensor cell 3. And start the measurement. The integrated flow rate of the sample gas or the standard gas supplied to the sensor cell 3 is monitored by the flow meter 4, and when the integrated flow rate reaches a preset value, the pump 5 is stopped to terminate the measurement. The signal processing unit 6 determines, for each oxide semiconductor sensor, a base resistance value Rb and a sensor resistance value (actual measurement value) R at the time of measurement of a sample gas or a standard gas.
The sensor output (−log (Rs / Rb)) is calculated based on s, and is sent to the PC 8 via the controller 7. PC8
Then, those sensor outputs are stored as measurement data.

FIG. 2 is a diagram showing an example of an odor map displayed by the PC 8. Three kinds of gases A, B and C each containing a different odor component were used as standard gases, and each standard gas was adjusted to three kinds of odor indexes and measured. The values of the three types of odor indexes are the same for gas A, gas B, and gas C.
On the odor map, the intersections of the sensor outputs when the respective standard gases of the two oxide semiconductor sensors CH1 and CH2 among the six oxide semiconductor sensors arranged in the sensor cell 3 are plotted are plotted. . The horizontal axis represents the sensor output (−log (Rs / Rb)) of the oxide semiconductor sensor CH1,
The vertical axis represents the sensor output (−lo) of the oxide semiconductor sensor CH2.
g (Rs / Rb)).

As shown in FIG. 2, when plots of the gas A, the gas B, and the gas C at the same odor index are connected by a line, an odor index line (broken line) such as a contour line is formed. By measuring a sample gas having an unknown odor index composed of odor components contained in gas A, gas B or gas C and plotting it on the odor map in FIG. 2, it is possible to predict the odor index of the sample gas. Can be. In this way, even a different odor species can be output with one parameter, the odor index, so that the labor of the sensory test can be reduced and reproducible measurement independent of the physical condition of the panelist can be performed. In this embodiment, six oxide semiconductor sensors are provided, and each sensor output can be obtained. However, when calculating the relational expression between the sensor output and the odor index, the object is achieved as shown in FIG. It is preferable to use the sensor outputs of the minimum number of oxide semiconductor sensors because the redundancy is reduced.

In this embodiment, an oxide semiconductor sensor is provided as a gas sensor. However, the present invention is not limited to this. A gas adsorption film is formed on the surface of a conductive polymer sensor or a quartz oscillator or a SAW device. A sensor may be used. In addition, the number of gas sensors is not limited to six, but may be two or more. In this embodiment, the sensor outputs of two gas sensors are used for analysis when creating an odor map. However, when an odor map is created using sensor outputs of three or more gas sensors, the dimension increases. Therefore, the data dimension may be reduced and displayed by performing a two-dimensional compression process on principal component analysis (PCA). As a method of calculating the relational expression between the sensor output and the odor index, in addition to creating an odor map, a multiple regression analysis method, a principal component regression analysis method, a PLS (Pa
A regression method such as a rtialLeast Squares) regression analysis method or a neural network method may be used. When such a method is used, commercially available software can be used, and examples thereof include SPSS (SPSS, USA) and Unscrambler (CAMO, USA).

[0014]

According to the odor measuring device of the present invention, the calculating section is based on the sensor outputs of two or more gas sensors when the odor index is measured for each of a plurality of standard gases whose odor indexes are known. Since a relational expression between the sensor outputs of two or more gas sensors and the odor index is calculated, and the odor index is calculated based on the relational expression and the sensor outputs of the two or more gas sensors when the sample gas is measured. An accurate odor index can be calculated even for an odor composed of a plurality of types of odor components.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing an example of an odor map displayed by a PC 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measurement gas container 2 Zero gas container 3 Sensor cell 3 Flow meter 5 Suction pump 5 Signal processing unit 7 Controller 8 Personal computer (PC) P1, P2, P3 Port V1, V2 Valve

Claims (1)

[Claims] 1. An odor measuring apparatus comprising two or more gas sensors having different response characteristics, wherein two or more gas sensors having different odor indexes are measured when the odor index is changed for each of a plurality of standard gases having known odor indexes. A relational expression between the sensor output of the two or more gas sensors and the odor index is calculated based on the sensor output, and the odor index is calculated based on the relational expression and the sensor output of the two or more gas sensors when the sample gas is measured. An odor measuring device comprising a calculation unit for calculating the odor.