JP3282586B2 - Odor 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 an odor measuring device for measuring an odor component contained in a sample gas using an odor sensor which is a kind of gas sensor. The odor measuring device according to the present invention is widely used for quality inspection of foods and fragrances, quantitative detection of odor pollution, fire alarm by detection of burnt odor, and further, criminal investigation such as tracking, identification, authentication and drug test of persons. Available in the field.

[0002]

2. Description of the Related Art An odor sensor electrically (or optically) converts a physical change of an odor component contained in air (or a supplied sample gas) caused by adhering to a sensitive surface of the sensor. It is to be measured. As an odor sensor, a sensor using an oxide semiconductor and a sensor using a conductive polymer are known. The odor measuring device uses such an odor sensor to determine, for example, what odor or odor an unknown odor substance has, or a substance such as "burnt odor" or "rot odor". Identification of smell, such as what category of smell is included,
Classification or positioning can be performed.

[0003] These odor sensors are based on the type of the material (for example, in the case of an odor sensor provided with a sensitive film made of a conductive polymer, the type of the conductive polymer and the type of dopant introduced for adjusting the conductivity). Etc.), the detectable compound differs. Also, in general, an odor sensor does not respond to only one type of compound but responds to a plurality of types of substances. Therefore, in order to measure an odorant in which a plurality of compounds are mixed, a plurality of odor sensors having different response characteristics are used, and a plurality of detection signals obtained from each of the odor sensors are comprehensively processed.

[0004]

The above processing is performed based on, for example, the absolute value of the level of each signal obtained from a plurality of sensors and the ratio of the signal levels of the plurality of sensors. Such processing enables relatively accurate discrimination when the output level is substantially linear with respect to the concentration of the substance, such as a conductive polymer sensor. However,
For example, when the output with respect to the concentration of the odor component is non-linear as in a metal oxide semiconductor sensor, there is a problem that it is difficult to determine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an odor measuring apparatus capable of accurately performing odor discrimination processing even when a sensor having nonlinearity with respect to concentration is used. It is to provide a device.

[0006]

Means for Solving the Problems The odor measuring apparatus according to the first invention, which has been made to solve the above-mentioned problems, comprises: a) adsorbing and holding an odor component in a sample gas introduced into an adsorbent; Gas preparation means for preparing the measurement gas by releasing the odor component from the adsorbent into the carrier gas by heating; andb) a sample gas flowing through the gas preparation means at the time of adsorption to adjust the measurement gas to a predetermined concentration. Concentration control means for setting the total flow rate or parameters related thereto, or the total flow rate of carrier gas flowing to the gas preparation means at the time of desorption, or parameters related thereto; andc) odor components in the measurement gas prepared at a predetermined concentration. A) detecting a plurality of measurement gases having different concentrations prepared from the same sample gas based on outputs detected by the plurality of detection means. It is characterized in that and a processing means for calculating an index characterizing the odor components contained in the material gas.

[0007] An odor measuring apparatus according to a second aspect of the present invention for solving the above-mentioned problems includes: a) gas preparation means for preparing a measurement gas obtained by concentrating or diluting a sample gas containing an odor component to a predetermined concentration; b) a plurality of detection means for detecting the odor component in the measurement gas, c) when a certain measurement gas is introduced into the plurality of detection means, based on the output obtained from each detection means Calculating means for performing a multivariate analysis calculation by analysis, d) using a calculation result obtained by the calculating means for a plurality of measurement gases having different concentrations prepared from the same sample gas, Means for identifying the odor;
It is characterized by having.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the odor measuring apparatus according to the first invention, a so-called thermal desorption type gas including, as gas preparation means, for example, a collection tube loaded with an adsorbent and a heating means for heating the adsorbent. Concentrating means can be used. In this configuration, a measurement gas is prepared in the following procedure. First,
The sample gas is caused to flow through the collection tube, and the odor components contained in the sample gas are adsorbed by the adsorbent. After the odor components are sufficiently adsorbed, a carrier gas (for example, nitrogen gas or the like) is supplied to the collection tube instead of the sample gas, and the adsorbent is heated by the heating means. Then, the adsorbed odor component is separated and diffused into the carrier gas. The measurement gas thus prepared is introduced into a plurality of detection means, and each detection means outputs a detection signal according to the corresponding odor component contained in the measurement gas. As the detection means, a sensor having a sensitive film, which changes the electrical characteristics of the sensitive film when odor component molecules adhere to the sensitive film can be used.

In the above gas preparation means, the total flow rate of the sample gas passing through the collection tube at the time of component adsorption and the total flow rate of the carrier gas passing through the collection tube at the time of separation and desorption are measured within a range in which the adsorption action is not saturated. The gas concentration (odor component concentration) is determined. Therefore, the concentration control means may control the total flow rate of the sample gas or a parameter related thereto, or the total flow rate of the carrier gas or a parameter related thereto (specifically, for example, the flow rate per unit time of the sample gas or the carrier gas or the flow time). Etc.) are set appropriately, and the concentration of the measurement gas is set to a predetermined value. When measurement of a plurality of measurement gases having different concentrations prepared from the same sample gas is performed, the arithmetic processing unit acquires detection signals from the plurality of detection units for each concentration. Then, a predetermined calculation is performed based on these detection signals, and an index characterizing the odor component contained in the sample gas is calculated. Examples of this arithmetic processing include arithmetic processing using various multivariate analysis techniques such as principal component analysis described later, and a method using an appropriate equation that approximates the relationship between the gas concentration and the output of the detection means. can do.

In the odor measuring device according to the second invention, the gas preparation means may be, for example, the gas preparation means described in the first invention. The calculation means uses a detection signal obtained from a plurality of detection means for a certain concentration of the measurement gas to perform principal component analysis (Principal Component Analysis).
ysis = PCA). The identification means identifies the odor of the odor component based on a plurality of analysis results obtained for a plurality of measurement gases containing the same odor component at different concentrations. For example, on a PCA score obtained as a result of the principal component analysis, a straight line or a curve connecting points obtained for a certain unknown odor component corresponding to different concentrations is obtained corresponding to different concentrations for other odor components. If they exist on the same line (including the extension line) as a straight line or a curve connecting the points, it is determined that both have the same or very similar tendency to smell. Therefore, with this configuration, the smell can be accurately identified and classified without being affected by the concentration dependency of the detection means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the odor measuring device according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram centering on the gas flow path of the odor measuring device of the present embodiment.

A flow path on the outlet side of a constant pressure valve 11 provided at a gas outlet of a nitrogen gas container 10 filled with pure nitrogen gas (N 2) has first and second flow control units 13 such as a mass flow controller, respectively. It is branched into two first and second nitrogen gas flow paths 12 and 15 having a molecular sieve filter 14 and a molecular sieve filter 17 for removing impurities. The three-way valve 20 selectively connects the sample gas flow path and the first nitrogen gas flow path 12 connected to the sample gas supply port 18 via the dust removing PTFE membrane filter 19 with a three-way valve (6-port 2-position valve). 21 port a. The second nitrogen gas flow path 15 is connected to the port d of the six-way valve 21. Hex valve 21
A heater 23 for heating is provided between the port c and the port f.
Is connected to the collection tube 22 provided with. The collection tube 22 is filled with, for example, a carbon-based adsorbent or another appropriate adsorbent according to the odor component to be measured.

The port b of the six-way valve 21 is selectively connected by a three-way valve 24 to a flow path that passes through the pump 25 and the flow meter 26 or a flow path that does not pass therethrough. The port e of the hexagonal valve 21 is connected to a first flow cell 28a having a plurality of odor sensors 29a.
The downstream outlet is connected to a plurality of odor sensors 29.
b is connected to the second flow cell 28b in which b is installed, and further downstream thereof is connected to the outlet 30. The odor sensor 29a is an odor sensor using, as a sensitive film, a conductive polymer having characteristics different in detection sensitivity from various odor components. On the other hand, the odor sensor 29b
Is an odor sensor using a metal oxide semiconductor having different detection sensitivities for various odor components as a sensitive film.

The air sucked from the air supply port 31 by the pump 32 is compressed and stored in the tank 33, and the outlet thereof is passed through a third flow control unit 34 and an activated carbon filter 35 for removing impurities. It is connected to the inlet of the second flow cell 28b. Thereby, the first flow cell 28
An appropriate amount of air can be mixed with the gas flowing from the flow cell a to the second flow cell 28b. Note that a configuration in which pure oxygen gas is mixed instead of air may be adopted. If pure oxygen gas is used, the volume to be mixed can be far reduced as compared with air, so that the rate of dilution of the odor component is small, which is advantageous for improving the sensitivity of detection by the odor sensor 29b.

Six-way valve 21, first and second flow cells 2
The whole of 8 a and 28 b is installed in a thermostat 36, and the thermostat 36 can be controlled to a predetermined temperature by a temperature controller 37. In addition, the plurality of odor sensors 29a, 2
The detection signal 9b is input to a signal processing unit 40 that performs processing such as identification and classification of odor components. Signal processing unit 4
0 denotes an A / D conversion unit 41 for converting an analog detection value into a digital value for each odor sensor, an operation processing unit 42 for executing a principal component analysis operation, which is one method of multivariate analysis, as described below, An odor discriminating unit 43 for discriminating the odor of the odor component based on the calculation result. Control unit 38
Has a function of controlling the three-way valves 20, 24, the six-way valves 21, the pumps 25, 32, the heater 23, the temperature adjusting unit 37, the signal processing unit 40, and the like according to a predetermined program, as described later. An operation unit 39 is provided for externally setting information necessary for control and the like.

Next, in the above-mentioned odor measuring device, sensor outputs (odor sensors 29a, 29a,
9b) will be described in detail in accordance with the measurement order.

(I) Collection of odor components First, the control unit 38 switches the three-way valve 20 so that the sample gas supply port 18 and the port a of the six-way valve 21 are connected, and simultaneously controls the port b of the six-way valve 21. The three-way valve 24 is switched so that is connected to the pump 25. The connection state indicated by the broken line in FIG.
And the pump 25 is operated. Then, by the suction force of the pump 25, the sample gas sucked from the sample gas supply port 18 is subjected to removal of relatively large suspended solids such as dust by the membrane filter 19, and is captured via the three-way valve 20 and the six-way valve 21. It is introduced into the collecting pipe 22 (from left to right in FIG. 1), and further, the six-way valve 21 and the three-way valve 2
4. The liquid is discharged from the discharge port 27 through the pump 25 and the flow meter 26. At this time, heating by the heater 23 is not performed.

Since the gas pressure at the gas outlet of the nitrogen gas container 10 is higher than the gas pressure at the outlet 30, the second nitrogen gas flow path 1
The nitrogen gas supplied through 5 flows through the first and second flow cells 28 a and 28 b through the six-way valve 21, and is discharged from the discharge port 30 to the outside. Thereby, the odor sensors 29a and 29b are always kept in the nitrogen gas atmosphere. At this time, the tank 3 is located on the side of the flow cell 28b.
The air sent from 3 may be mixed with the nitrogen gas to flow.

As described above, when the sample gas passes through the collection tube 22, the odor components contained in the sample gas are adsorbed by the adsorbent. At this time, the amount of the odor component adsorbed by the adsorbent is substantially proportional to the total flow rate of the sample gas passing through the collection tube 22 within a range where the adsorption capacity is not saturated. Therefore, under the condition that the flow rate per unit time is constant, it is almost proportional to the flow time of the sample gas, and under the condition that the flow time is constant, it is almost proportional to the flow rate per unit time. However, in practice, when the flow rate per unit time is increased to a certain extent, the odor component molecules may pass through without contacting the adsorption surface. The amount can be controlled more precisely. Therefore, in the present embodiment, the control unit 38 controls the suction force of the pump 25 so that the value detected by the flow meter 26 becomes a predetermined constant value, and sets the total flow rate set by the operation unit 39 or a parameter based on the total flow rate. The flow time of the sample gas is changed according to the conditions.

(Ii) Replacement of Gas in Collection Tube After the passage of the flow time, the control unit 38 switches the three-way valve 20 to connect the first nitrogen gas flow path 12 to the six-way valve 2.
One port a is connected, and the three-way valve 24 is switched to connect the port b of the six-way valve 21 directly to the outlet 27. Then, instead of the sample gas, the nitrogen gas supplied from the nitrogen gas container 10 is supplied to the first nitrogen gas flow path 12.
The gas passes through the three-way valve 20, the six-way valve 21, the collection pipe 22, the six-way valve 21, and the three-way valve 24, and is discharged from the discharge port 27. Thus, the sample gas remaining inside the flow path including the collection tube 22 is pushed out to the outside by the nitrogen gas. At this time, since the heating by the heater 23 is not performed, the odor component previously adsorbed by the adsorbent remains as it is. On the other hand, nitrogen gas is extremely dry, so most of the water adsorbed on the adsorbent and the water adhering to the inner wall of the flow channel are volatilized in the nitrogen gas and carried away. Thereby, dehumidification to a certain extent is achieved.

(Iii) Introduction of Odor Components into Odor Sensor After flowing nitrogen gas through the collection tube 22 for an appropriate time, the control unit 38 switches the six-way valve 21 to a connection state shown by a solid line in FIG. . Then, a flow path of the second nitrogen gas flow path 15-the hexagonal valve 21-the collection pipe 22-the hexagonal valve 21-the first flow cell 28a-the second flow cell 28b-the outlet 30 is formed. In this state, the heater 23 is energized to rapidly heat the collection tube 22 (for example, at a temperature rising rate of about 10 ° C./sec). As a result, the odor component adsorbed by the adsorbent in the collection tube 22 is separated from the adsorbent, and rides on the nitrogen gas flowing in the opposite direction (from right to left in FIG. 1) to the previous one. It is carried to one flow cell 28a. Here, the total flow rate of the nitrogen gas passing through the collection tube 22 during the period from when the heating of the collection tube 22 is started to when the odor components are almost completely removed from the adsorbent is determined in the above (i). 2
If the total flow rate of the sample gas passing through 2 is less than
The concentration of the measurement gas (odor component concentration) introduced into the flow cell 28a is higher than the concentration of the sample gas. That is, even if the amount of the odor component adsorbed by the adsorbent is the same, the concentration of the measurement gas introduced into the first flow cell 28a changes by changing the total flow rate of the nitrogen gas when the odor component is desorbed. Therefore, here, the flow rate of the nitrogen gas per unit time and the flow time thereof are always kept constant so that the concentration of the measurement gas changes only by the flow time of the sample gas.

When the temperature of the collecting tube 22 changes, the flow resistance changes. However, if a secondary pressure fluctuation type mass flow controller of a mechanical control type is used for the second flow control unit 16, for example, Even if the flow path resistance of the path fluctuates, the flow rate of the passing nitrogen gas can be kept constant. In addition,
In order for this mass flow controller to operate normally, the pressure difference between the inlet side pressure and the outlet side pressure must be maintained at a certain level or more. The set pressure, the inner diameter of the pipe, the flow rate of the air mixed through the third flow control unit 34, and the like are determined. Thus, the flow rate of the nitrogen gas is accurately controlled, and the mixed gas does not flow back to the first flow cell 28a from the location where the air is mixed.

As described above, when the measurement gas passes through the first flow cell 28a, the odor component is adsorbed on the sensitive film made of the conductive polymer of the odor sensor 29a.
The electrical resistance between the electrodes 9a changes. The detection signal due to the resistance change is sent to the signal processing unit 40.

The air stored in the tank 33 is
The flow rate is adjusted to an appropriate flow rate by the flow rate control unit 34, and after the undesired components that cause disturbance in the measurement are removed by the activated carbon filter 35, the flow rate is mixed into the measurement gas that has passed through the first flow cell 28a. Because air contains oxygen gas,
Oxygen gas flows into the second flow cell 28b together with the odor component, and the oxygen gas molecules are adsorbed on the sensitive film made of a metal oxide semiconductor, thereby causing an oxidation-reduction reaction with the odor component molecules. As a result, the conductivity of the odor sensor 29b changes, and the electrical resistance between the electrodes changes. The detection signal due to this resistance change is also sent to the signal processing unit 40.

During these measurements, the six-way valve 21,
The first and second flow cells 28a and 28b and the flow path connecting them are maintained at a constant temperature (for example, about 40 ° C.) slightly higher than room temperature by the temperature adjustment unit 37. As a result, the odor sensors 29a, 29
In addition to reducing the influence of b, it is possible to prevent the high-boiling compound from adhering to the inner wall of the flow path and the like, thereby preventing the stability of the detection sensitivity from being impaired.

Since the plurality of odor sensors 29a and 29b have different selectivity and response characteristics, for example, a large detection signal is obtained from a certain odor sensor for a certain odor component, In some cases, no detection signal can be obtained from the sensor. Therefore, the signal processing unit 40 performs multivariate analysis processing using the plurality of detection signals obtained as described above, thereby comprehensively identifying or classifying the smell. Although various methods of multivariate analysis are known, here, principal component analysis (PCA) is used as described later.

(Iv) Purification of Odor Sensor As described above, when the odor components adsorbed on the adsorbent of the collection tube 22 are sufficiently released, the control unit 38 controls the six-way valve 21 again as shown in FIG. Is switched to the connection state indicated by the broken line, and the temperature of the thermostatic bath 36 is raised to a predetermined temperature by the temperature adjustment unit 37. Thereby, the first and second flow cells 2
A clean nitrogen gas flows through 8a and 28b. When the temperature of the odor sensors 29a and 29b rises, the odor components and other impurities adsorbed on the sensitive film are easily released, and are exhausted from the outlet 30 on the nitrogen gas.
As a result, the sensitive films of the odor sensors 29a and 29b recover and return to a state where the odor components can be detected again.

Next, an example of a procedure for measuring a certain type of sample gas in the above-mentioned odor measuring device will be described with reference to the flowchart of FIG. First, the measurer appropriately designates three different densities from the operation unit 39. The score of the concentration is not limited to this, and instead of specifying the concentration, other parameters corresponding to the concentration (such as the total flow rate of the sample gas and the flow time of the sample gas) may be directly input. Good. Here, the concentration is P
[%], Three points of P × 2 and P × 4 are designated.
In this embodiment, the measurement gas is supplied to the first flow cell 28a.
Since the air (or oxygen gas) is mixed in after passing through the second flow cell 28b, strictly speaking, the concentration of the measurement gas decreases at the time of passing through the second flow cell 28b, but the flow rate of the nitrogen gas is lower than the flow rate of the air. If is also large enough, this reduction in concentration can be ignored. Even in such a case, if the flow rate of the air is kept constant, the amount of change in concentration during the flow from the first flow cell 28a to the second flow cell 28b can be calculated. Thus, it is possible to cope with the case where the concentration specified at the time of passing through any of the flow cells. In the following description, it is assumed that the flow rate of the mixed air is small and the concentration of the measurement gas does not change.

In response to the above designation, the control unit 38 calculates the sample gas flow time corresponding to those concentrations based on a predetermined formula. As described above, if the flow rate of the sample gas per unit time and the total flow rate of the nitrogen gas at the time of odor separation and separation are constant, the concentration of the measurement gas is proportional to the flow time of the sample gas. The time is t [seconds], t ×
2, t × 4.

When the measurement is started, the control unit 38 first sets the sample gas flow time at the time of component adsorption to t (step S1), and executes a series of measurements in the order described above (step S2). ). As a result, the measurement gas having the concentration P flows through the first and second flow cells 28a and 28b.
The arithmetic processing unit 42 acquires detection signals obtained from the respective odor sensors 29a and 29b via the A / D conversion unit 41,
These are temporarily stored in an internal memory (step S
3).

In the first measurement, the odor sensor 29
When the cleaning of a and 29b is completed, the control unit 38
Next, the same measurement is performed with the sample gas flow time during component adsorption set to t × 2 (steps S4 and S5). As a result, the concentration P is stored in the first and second flow cells 28a and 28b.
Since × 2 measurement gas flows, the arithmetic processing unit 42 stores the detection signals obtained from each of the odor sensors 29a and 29b at this time in an internal memory (step S6). After the second measurement, the same measurement is performed by setting the sample gas circulation time at the time of component adsorption to t × 4, and the arithmetic processing unit 42 calculates the concentration P
A detection signal for the × 4 measurement gas is obtained and stored in an internal memory (steps S7 to S9). In this way, the detection signals of the respective odor sensors 29a and 29b for the measurement gases having the concentrations P, P × 2 and P × 4 are obtained.

The arithmetic processing section 42 executes an arithmetic processing for principal component analysis using detection signals obtained from the plurality of odor sensors 29a and 29b for each concentration (step S1).
0). Principal component analysis is to express a large number of variables (six in the example of FIG. 3 described below) with a smaller number of index values (three in this case). For more details, Yoshikatsu Miyashita and Shinichi Sasaki "Chemometrics" Kyoritsu Publishing (1995)
And the like describe the method. In addition, various types of software are available for performing arithmetic processing of principal component analysis on a personal computer or a workstation. For example, SPSS (Statistical Packages)
for Social Sciences) (SPSS Co., Ltd.)
Is well known.

When the above-mentioned index value (factor) is set to three, the result of the principal component analysis is represented by a point (hereinafter referred to as “score point”) on a graph (PCA score) having three factor axes as shown in FIG. "). Therefore, when the measurement and processing are performed on the measurement gas having three concentrations prepared from the same sample gas as described above,
In the PCA score, each score point usually appears at three positions apart from each other. Note that the arithmetic processing unit 42
It is not necessary to wait until the measurement up to step S9 is completed, and when the detection signal for each concentration is obtained in the first and second measurements, the calculation processing of the principal component analysis for that concentration can be started. it can.

After all the principal component analysis calculation processing is completed,
The odor component is identified using the calculation result (step S11). Hereinafter, a method of identifying an odor in the odor identification unit 43 of this embodiment will be described using an example in which three types of sample gases A, B, and C are measured by the odor measurement device. In this example, the concentration was adjusted to three concentrations of P, P × 2, and P × 4 by using six odor sensors 29b each having a sensitive film made of a metal oxide semiconductor provided in the second flow cell 28b having the above configuration. The measurement gas is being measured. In addition, in consideration of the variation in the measurement, the same sample gas and the same concentration are measured three times each.

FIG. 3 shows the PCA score obtained by this measurement. In FIG. 3, for example, (A, P) indicates the result of the principal component analysis for the measurement gas having the concentration P prepared from the sample gas A. It is the score point shown. In the PCA score, the distance between score points is short for those having a close relationship to each other. As is clear from FIG. 3, the same sample gas and the same concentration
The score points corresponding to each measurement are located very close to each other. In FIG. 3, these are surrounded by the same elliptical frame. On the other hand, score points corresponding to different concentrations of the same sample gas are located apart from each other.
Therefore, as shown by a dashed line in FIG. 3, a line connecting the score points separated from each other (hereinafter, referred to as a “concentration-dependent line”).
Draw. In FIG. 3, concentration-dependent lines for sample gases A, B, and C are denoted by a, b, and c, respectively.

The odor discriminating section 43 determines the similarity of the odors based on the positional relationship of the density-dependent lines. For example, when the concentration-dependent lines of two kinds of sample gases are substantially on the same line, it can be determined that they have the same tendency or the same category of smell. In addition, even if they are not on the same line, if they are oriented in the direction of the parallel translation and the distance is short, it can be determined that the smell has a relatively close tendency. Conversely, when the distance between the two density-dependent lines is large or the intersection angle is large, it can be determined that the odors have different tendencies. In the case of the example of FIG. 3, since the concentration-dependent lines a, b, and c are separated from each other, the three types of sample gases A, B, and C (or the odor components contained therein) all have different odors. Can be determined to be.

In general, the determination of the similarity of the odor can be performed more precisely as the number of the odor sensors is larger and the odor sensor having a higher selectivity is used. For example, when an odor sensor having relatively low selectivity (that is, having a similar response characteristic to a plurality of the same type of components) is used, when the concentration-dependent lines of two types of sample gases are on the same line, Although it is possible to determine that the odors have the same tendency, it is difficult to determine that the components themselves are exactly the same. However, when an odor sensor having high selectivity (that is, having a particularly strong response characteristic to a certain specific component) is used, when the concentration-dependent lines of the two types of sample gases are on the same line, It can be determined that there is a high possibility that the same odor component is contained.

In the example of FIG. 3, the concentration-dependent lines a, b,
Although c is almost a straight line, it is not always a straight line. Therefore, it is desirable to set three or more measurement concentrations for the same sample gas. As described above, the odor measuring device of the present embodiment can identify the odor of the sample gas based on the positional relationship of the concentration-dependent line on the PCA score.

Next, the non-linear concentration dependence of the odor sensor is corrected by using the detection signals obtained by the odor sensor for a plurality of measurement gases having different concentrations prepared from the same sample gas as described above. Another processing method for performing accurate odor identification will be described. FIG. 4 is a diagram showing the concept of this method. The concentration dependency of each odor sensor, that is, the relationship between the concentration and the detection signal should be able to be expressed by an already known approximate expression. Since this approximate expression includes a constant depending on the type of the odor component, etc., by giving detection signals at a plurality of concentrations as shown in FIG. 4, the approximate expression is solved (that is, the broken line curve in FIG. 4). (Confirm the approximate expression as shown in (1)) to obtain a constant. Then, by comparing the constants calculated for a plurality of sample gases,
Smell identification.

For this purpose, various approximation formulas already proposed can be used. For example, PK Clifford et al., Sensors and Actuators 3 [1982/83].
) 3) “Characteristics of
Semiconductor Gas Sensors One. Steady
State Gas Response (Characteristics of sem
iconductor gas sensorsI. Steady state gas respons
e)), the metal oxide semiconductor sensor
The approximate expression of (1) is proposed. (R / R0) ^{-(1 / k)} = (1 + ^K.Gn ) / O (1) where R is a sensor resistance (detection value), R0 is a sensor resistance in an air atmosphere (initial value), G Is a measured gas concentration, O is an oxygen gas concentration, and k, K and n are constants.

The initial sensor resistance R0 can be measured by a preliminary experiment or the like, and these values are known since the oxygen gas concentration O depends on the flow rate of the mixed air or oxygen gas. Therefore, unknown constants k, K, and n can be calculated by substituting the measured gas concentration G and the value of the sensor resistance R at that time into the above equation (1).

Further, as another example of the approximate expression, Rajeev K. Srivastava et al., Published by Sensors and Actuators B21 (1994).
s and Actuators B21), “Sensing Mechanism in Tin Oxide-Based Thick-
Film Gas Sensors (Sensing mechanism inti
n oxide-based thick-film gas sensors). Log (R / R0) = - BG b ... (2) wherein, R, R0, G is the same definition as above (1), B
And b are constants.

The approximate expression that can be used is not limited to the above example, and it is desirable to use an optimal approximate expression for each type of sensor used. Further, even when the number of constants in such an approximate expression is large, not all of the constants depend on the type of the odor component. Therefore, since a part of the constant may be fixed to a certain value in some cases, it is not always necessary to increase the number of measured concentrations even if the approximate expression is complicated. Also, there are cases where a certain approximate expression is applicable only within a predetermined gas concentration range. In such a case, the range of the measured concentration that can be specified from the operation unit 39 may be limited first.

It should be noted that the above embodiment is merely an example, and it is apparent that modifications and modifications can be made within the spirit of the present invention. For example, instead of the right side of equation (2), G ^h / (1+
G ^h ) or {G / (1 + G)} ^h (h is a constant). In the above embodiment, the sample gas flow time is changed to change the concentration of the measurement gas. However, as described above, by changing other parameters, the concentration of the measurement gas is set to a set value. You can also

[0045]

As described above, in the odor measuring device according to the first invention, a plurality of detecting means (odor sensors) are provided.
By installing a collecting means (collecting tube) at the preceding stage, the total flow rate of the sample gas flowing through the collecting tube at the time of component adsorption or the total flow rate of the carrier gas flowing through the collecting tube at the time of separation and separation is controlled. The concentration of the odor component in the measurement gas to be introduced into the detection means is adjusted to a predetermined value, and a plurality of measurement gases having different concentrations prepared from the same sample gas are obtained by the respective detection means when introduced into the detection means. Odor identification is performed based on the output. Therefore, when a plurality of concentrations are set and measurement is performed, the concentration of the measurement gas introduced into the detection means can be made accurate, and the concentration dependency of the output of the detection means can be accurately obtained. As a result, the odor can be identified more accurately.

Further, in order to adjust the concentration of the measurement gas,
For example, it is only necessary to control the time during which the sample gas flows through the collection tube during component adsorption, the flow rate of the carrier gas through the collection tube during separation and desorption, and the like, so that the concentration can be easily adjusted and is also suitable for automatic measurement. Therefore, a complicated operation is not required at the time of measurement, and efficient measurement can be performed. In addition, space can be saved by incorporating the collection tube integrally with the odor measurement unit.

In the odor measuring apparatus according to the second invention, when a plurality of measurement gases prepared from the same sample gas and having different concentrations are respectively introduced into the detection means, the principal component analysis is performed by using the outputs obtained by the detection means. The characteristics of each sample gas are calculated as, for example, a concentration-dependent line on a PCA score, and the odor of the sample gas is characterized by comparing the characteristics. Therefore, even if the concentration dependency of the output of the detection means is non-linear, it is possible to accurately identify and classify the odor without being affected by the non-linearity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an odor measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a measuring procedure in the odor measuring device.

FIG. 3 is a view showing a PCA score showing an example of a result of principal component analysis.

FIG. 4 is a conceptual diagram of an odor discrimination processing method using an approximate expression indicating a relationship between a gas concentration and an output of an odor sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Nitrogen gas container 11 ... Constant pressure valve 12,15 ... Nitrogen gas flow path 13,16,34 ... Flow control part 18 ... Sample gas supply port 20,24 ... Three-way valve 21 ... 6-way valve 22 ... Collection pipe 23 ... Heater 25, 32 Pump 26 Flow meter 27, 30 Outlet 28a, 28b Flow cell 29a Odor sensor (conductive polymer) 29b Odor sensor (metal oxide semiconductor) 31 Air supply port 33 Tank 36 Constant temperature bath 37 temperature control unit 38 control unit 39 operation unit 40 signal processing unit 41 A / D conversion unit 42 arithmetic processing unit 43 odor identification unit

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Nakano 1 Nishinokyo Kuwaharacho, Nakagyo-ku, Kyoto Shimazu Seisakusho Sanjo Plant (56) References JP-A-11-118744 (JP, A) JP-A-11- 125612 (JP, A) JP-A-11-125613 (JP, A) JP-A-11-125610 (JP, A) JP-A-11-125614 (JP, A) JP-A-11-174012 (JP, A) JP-A-11-218512 (JP, A) JP-A-8-304317 (JP, A) JP-A-10-19862 (JP, A) Junichi Ide, Takamichi Nakamoto, Toyoei Moriizumi, Symposium on taste and smell Shu, Japan, 26, 345-348 Atsushi Fukuda, Takamichi Nakamoto, Toyosaka Moriizumi, Yasuo Asakura, IEICE Technical Report, Japan, VOL90 / NO52, 13-18 Mitsuo Soike, Yutaka Kurioka, Odor Applied Engineering, Japan, 1994 January 25, 159-166 (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 27/12 G01N 5/02

Claims (2)

(57) [Claims] 1. a) Gas preparation for preparing a measurement gas by adsorbing and holding an odor component in an introduced sample gas by an adsorbent and then releasing the odor component from the adsorbent into a carrier gas by heating. Means, b) to adjust the measurement gas to a predetermined concentration, the total flow rate of the sample gas flowing to the gas preparation means at the time of adsorption or parameters related thereto, or the total flow rate of the carrier gas flowing to the gas preparation means at the time of desorption, or Concentration control means for setting related parameters; c) a plurality of detection means for detecting odor components in a measurement gas prepared at a predetermined concentration; and d) a plurality of concentration differences prepared from the same sample gas. Arithmetic processing means for calculating an index characterizing an odor component contained in the sample gas, based on outputs detected by the plurality of detection means with respect to the measurement gas. An odor measuring device characterized by the following. 2. a) gas preparation means for preparing a measurement gas obtained by concentrating or diluting a sample gas containing an odor component to a predetermined concentration; b) a plurality of detection means for detecting the odor component in the measurement gas; c. A) when a certain measurement gas is introduced into the plurality of detection means, a calculation means for performing a multivariate analysis calculation by principal component analysis based on the output obtained from each detection means, d) from the same sample gas An odor measuring device comprising: an identification unit for identifying the odor of the sample gas by using a calculation result obtained by the calculation unit for a plurality of prepared measurement gases having different concentrations.