JP3501033B2 - Odor measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an odor measuring apparatus provided with two or more gas sensors having different response characteristics. Such an odor measuring apparatus is used for identifying or identifying an odor in the fields of deodorization, aroma, food management, malodor measurement, and the like. [0002] Regarding the odor measurement, 22 types of odor control substances specified by the Environment Agency, such as methyl mercaptan and trimethylamine, are determined by the official law (September 8, 1993, Environment Agency Notification No. 72, Odor Control). Material analysis method matrix (see amendment) has been established, and sample gas collection, concentration, and measurement methods are defined. For substances other than odor-controlling substances, a method called the three-point odor bag method, which is conducted under the guidance of an odor judge, is performed. In that method, 6 panelists who are recognized as having a normal sense of smell are
Using more than one person, each panelist will be given one scented odor bag with sample gas injected into odorless air and two odorless odor bags sealed with odorless air, and will select one odor bag to determine that sample gas has been injected. Then, the odor index is calculated by a predetermined formula based on the selection result of each panel (see Environmental Agency Notification No. 63, September 13, 1995, Method of calculating the odor index). However, the official methods described above have the problem that the measurement methods for each offensive odor control substances are different and the operation thereof is complicated, and it is difficult to obtain an accurate value unless it is entrusted to a specialist. Moreover, since measurement takes time, there exists a fault that it is unsuitable for on-site measurement.
In the three-point odor bag method, it is necessary to collect six or more panelists, so it is not easy, and there is a concern about the influence on the human body because the panelists need to smell bad odors. In order to solve such problems, a malodor measuring device using a gas sensor has been proposed, and as one of them, an odor index meter XP-349S (manufactured by New Cosmos Electric Co., Ltd.) capable of easily measuring malodors. Is on sale. This odor index meter includes one oxide semiconductor sensor that utilizes a phenomenon in which the electrical resistance of an oxide semiconductor changes due to an oxidation-reduction reaction with a malodorous substance in a sample gas. [0004] Since the odor index meter has only one gas sensor, when the odor composed of one kind of odor component is targeted, the odor index Although a correlation can be obtained, when an odor composed of a plurality of types of odor components is targeted, it is impossible to associate the odor index with the difference in sensitivity of the gas sensor with respect to the type of odor components. Accordingly, an object of the present invention is to provide an odor measuring apparatus capable of accurately calculating an odor index even if it is composed of a plurality of odor components. The present invention is an odor measuring apparatus provided with two or more gas sensors having different response characteristics, and the odor index for each of a plurality of types of standard gases with known odor indices. Based on the sensor output of two or more gas sensors when measured while changing, the relational expression between the sensor output of two or more gas sensors and the odor index is calculated, and the relational expression and two when the sample gas is measured An arithmetic unit that calculates an odor index based on the sensor output of the gas sensor is provided. The measurement is performed by changing the odor index for each of a plurality of standard gases having known odor indices. The calculation unit
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 measuring the sample gas, the odor index is calculated based on the relational expression. Therefore, an accurate odor index can be calculated even if the odor is composed of a plurality of types of odor components. FIG. 1 is a schematic block diagram showing an embodiment.
A measurement gas container 1 in which a sample gas or a standard gas with a known odor index is accommodated is provided. Oxygen necessary for the 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. There is provided a zero gas container 2 in which a zero gas made of clean air containing oxygen is accommodated. Zero gas container 2 is 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, there is a valve V
Either the measurement gas container 1 or the zero gas container 2 is connected by opening and closing 1 and V2. In the sensor cell 3, six oxide semiconductor sensors having different response characteristics are arranged. The outlet side of the sensor cell 3 is a flow meter 4
Is connected to the suction side of the suction pump 5. A 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 that calculates the 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. A flow meter 4 and a pump 5 are also electrically connected to the controller 7, and the controller 7 controls the operation of the pump 5 based on a flow rate 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 connecting the zero gas container 2 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 zero gas to the sensor cell 3,
Clean the flow path system. The zero gas supplied to the sensor cell 3 is connected to the port P via the flow meter 4 and the pump 5.
3 is discharged. 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 connecting the measurement gas container 1 containing the sample gas or standard gas to the port P1, the valve V2 is closed to stop the supply of zero gas, and the valve V1 is opened to supply the sample gas or standard gas to the sensor cell 3. To start measurement. The integrated flow rate of the sample gas or 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 and the measurement is finished. For each oxide semiconductor sensor, the signal processing unit 6 uses the base resistance value Rb and the sensor resistance value (measured value) R when measuring the sample gas or the standard gas.
The sensor output (−log (Rs / Rb)) is calculated based on s and 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. As the standard gas, three types of gas A, gas B and gas C each containing different odor components were used, and each standard gas adjusted to three types of odor index was measured. The three types of odor index values are the same for gas A, gas B, and gas C.
On the odor map, the intersection points of the sensor outputs when the standard gases of the two oxide semiconductor sensors CH1 and CH2 are measured among the six oxide semiconductor sensors arranged in the sensor cell 3 are plotted. . The horizontal axis represents the sensor output of the oxide semiconductor sensor CH1 (−log (Rs / Rb)),
The vertical axis represents the sensor output of the oxide semiconductor sensor CH2 (−lo
g (Rs / Rb)). As shown in FIG. 2, when plots of the same odor index of gas A, gas B and gas C are connected by a line, an odor index line (broken line) such as a contour line is formed. Measure the odor index unknown odor sample gas composed of odor components contained in gas A, gas B or gas C, and plot it on the odor map in Fig. 2 to predict the odor index of the sample gas Can do. Thus, since different odor species can be output with one parameter called the odor index, the labor of the sensory test can be reduced, and reproducible measurement independent of the physical condition of the panel 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 output of a 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, and a gas adsorbing film is formed on the surface of a conductive polymer sensor or a crystal resonator or SAW device. A sensor may be used. Further, the number of gas sensors is not limited to six, and may be two or more. In this embodiment, when the odor map is created, the sensor outputs of two gas sensors are used for analysis. However, when the 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 through principal component analysis (PCA). As a method for 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, PLS (Pa
(rtialLeast Squares) A regression method such as a 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 Unscrambling (CAMO, USA). According to the odor measuring apparatus of the present invention, sensor outputs of two or more gas sensors when the arithmetic unit changes the odor index for each of a plurality of types of standard gases whose odor index is known. And calculating a relational expression between sensor outputs of two or more gas sensors and an odor index, and calculating an odor index based on the relational expression and sensor outputs of two or more gas sensors when measuring the sample gas. Therefore, an accurate odor index can be calculated even if the odor is composed of a plurality of types of odor components.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing an example of an odor map displayed by the PC 8. FIG. [Explanation 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 Ports V1, V2 Valve

Continuation of Front Page (56) References JP-A-8-94567 (JP, A) JP-A-2-110361 (JP, A) JP-A-6-50868 (JP, A) JP-A-5-180746 (JP) JP, 5-99868 (JP, A) JP 9-21773 (JP, A) JP 2001-33362 (JP, A) JP 2-110361 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G01N 27/00-27/12

Claims (1)

(57) [Claims] [Claim 1] In an odor measuring apparatus having two or more gas sensors having different response characteristics, measurement is performed by changing the odor index for each of a plurality of kinds of standard gases having known odor indices. Based on the sensor outputs of the two or more gas sensors, the relational expression between the sensor outputs of the two or more gas sensors and the odor index is calculated, and the relational expression and the two or more when the sample gas is measured are calculated. An odor measuring apparatus comprising an arithmetic unit for calculating an odor index based on a sensor output of a gas sensor.