JP3226066B2 - Odor concentration meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus used for measuring offensive odor and the like, and more particularly to an odor concentration meter for detecting odorous substances using a quartz oscillator or a surface acoustic wave device.

[0002]

2. Description of the Related Art Conventionally, an odor sensory test method has been used for measuring the odor concentration, and the odor concentration has been actually measured using the human sense of smell. For example, a three-point comparison odor bag method, which is one method of the odor sensory test method, has been adopted as a method for measuring offensive odor by local governments such as Tokyo.

Here, the three-point comparison type odor bag method will be described. In the three-point comparison odor bag method, first, three bags are prepared and 2 bags are prepared.
One bag is made odorless, and the other bag is filled with a sample diluted to a predetermined dilution ratio.

A person who performs a test (hereinafter, referred to as a panel)
Smells the smells of the three bags, and selects the bag that is considered to smell. If the selected bag encapsulates the diluted sample, that is, if the answer is correct, the dilution factor is set to about 3 and the panel is selected again. Then, the panel selects an odorless bag, that is, repeats the above test until an incorrect answer is obtained.

[0005] Here, the geometric mean of the maximum dilution ratio that the panel correctly answers and the dilution ratio that is incorrectly answered is the olfactory threshold of the panel. This test method is performed by a panel of a plurality of persons, and an average value obtained by removing the maximum and minimum olfactory thresholds from the obtained olfactory thresholds is defined as the odor concentration of the odor.

As a conventional odor concentration measuring method using a quartz oscillator, there is an odor concentration measuring system as described in Japanese Patent Application Laid-Open No. 4-50637.

In the odor concentration measuring system, the odor concentration is measured by once logarithmically converting the output signal from the quartz oscillator as a sensor, and again performing antilogarithmic conversion of the value multiplied by the sensitivity multiple.

[0008]

However, the above-mentioned odor sensory test method is based on the sense of smell of human beings, so that the measured values are apt to vary, and the test is performed by a plurality of humans, which takes time. There is.

Further, in the odor concentration measurement system using the above-described quartz oscillator, it is necessary to perform logarithmic conversion and antilogarithmic conversion once each, so that the circuit scale becomes large in hardware, and the software becomes large. There is a problem that the operation time becomes long. Therefore, an object of the present invention is to realize an odor concentration meter capable of measuring odor concentration and the like with a simple configuration.

[0010]

In order to achieve the above object, according to a first aspect of the present invention, there is provided an odor concentration meter for measuring the concentration of an odor substance, wherein a quartz oscillator having an odor-sensitive film adhered to the surface thereof is provided. Alternatively, a sensor composed of a surface acoustic wave element, an oscillation circuit for driving the sensor to resonate at a resonance frequency, a counter for measuring the oscillation frequency of the oscillation circuit, and measurement in advance from a measurement value output from the counter
And a calculation control means for calculating the odor concentration by subtracting the measured value at the time of no odor and multiplying by a proportional coefficient.

A second aspect of the present invention is characterized in that, in the second aspect of the present invention, a calculation control means for calculating an odor index from an odor concentration is provided.

[0012]

The odor concentration is obtained by multiplying the change amount of the resonance frequency of the sensor by the proportional coefficient. The odor concentration is obtained by logarithmically converting the odor concentration and multiplying the conversion result by ten.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of an odor concentration meter according to an embodiment of the present invention. In FIG. 1, 1 is a sensor, 2 is an oscillation circuit, 3 is a counter, 4 is a timer circuit, 5 is a microprocessor which is an arithmetic control means, 100, 101 and 103.
Is a control signal, and 102 is a data signal.

The output of the sensor 1 is connected to an oscillation circuit 2,
The output of the oscillation circuit 2 is connected to the counter 3. The control signal 101 from the timer circuit 4 and the data signal 102 and the control signal 103 from the microprocessor 5 are connected to the counter 3, respectively.

The control signal 101 from the timer circuit 4
Is connected to the microprocessor 5, and a control signal 100 from the microprocessor 5 is connected to the timer circuit 4.

Here, the operation of the embodiment shown in FIG. 1 will be described. The sensor 1 has a film containing an amphipathic molecule such as lipid (hereinafter referred to as a lipid film) attached to the surface of a quartz oscillator or a surface acoustic wave device as an odor-sensitive film. The resonance frequency changes. The sensor 1 is arranged in the sample to be measured, and resonates by driving from the oscillation circuit 2.

The timer circuit 4 starts operating in response to a control signal 100 from the microprocessor 5, and the control signal 10
1 controls the operation and stop timing of the counter 3.

Further, the microprocessor 5 receives the control signal 101 from the timer circuit 4, outputs a control signal 103 to the counter 3, takes out the measured value in the counter 3 as a data signal 102, and initializes the counter 3 Become Further, calculation such as odor concentration is performed based on the data signal 102.

Here, the operation of the arithmetic processing in the microprocessor 5 in FIG. 1 will be described with reference to FIG. 2 and FIG.
FIG. 2 is a functional block diagram showing the arithmetic processing in the microprocessor 5 in hardware, and FIG. 3 is a flowchart of the arithmetic processing in the microprocessor 5.

In FIG. 2, 1, 2 and 3 are given the same reference numerals as in FIG. 1, 6 is a storage circuit, 7 is a subtraction circuit, 8 and 10 are multiplication circuits, 9 is a logarithmic circuit, 104 is an odor concentration signal. , 105 are odor index signals.

The sensor 1 is connected to an oscillation circuit 2, and the output of the oscillation circuit 2 is connected to a counter 3. The output of the counter 3 is connected to one input terminal of the subtraction circuit 7, and the other input terminal of the subtraction circuit 7 is connected to the output of the storage circuit 6.

The output of the subtraction circuit 7 is connected to a multiplication circuit 8, and the output of the multiplication circuit 8 is output as an odor concentration signal 104 and is connected to a logarithmic circuit 9. The output of the logarithmic circuit 9 is connected to a multiplying circuit 10. Further, the multiplication circuit 10 outputs an odor index signal 105.

In the circuit as shown in FIG. 2, the sensor 1 is arranged in the sample to be measured and resonates by driving from the oscillation circuit 2. This resonance frequency signal is input to the counter 3 and the frequency is measured.

The measurement in the absence of the odorant in the storage circuit 6, that is, the measurement value at odorless is previously stored, multiplied in the subtraction circuit 7 from the output signal of the counter 3 is subtracted the offset value is Input to the circuit 8.

The multiplication circuit 8 multiplies the subtraction result by a coefficient,
The odor concentration signal 104 is output. Further, the odor concentration signal 104 is logarithmically converted by the logarithmic circuit 9 and the multiplication circuit 1
After being multiplied by 10 at 0, it is output as the odor index signal 105.

On the other hand, the flowchart shown in FIG. 3 shows the operation when the timer circuit 4 is not used. FIG.
In "ST1", the counter 3 is initialized.
In ST2 ", the counter 3 is started.

Next, a predetermined time is waited in a loop of "ST3" in FIG.
Read the measured value from. The value when there is no odor substance in "ST5" in FIG. 3 is subtracted from the measured value obtained in "ST4" in FIG.

In "ST6" in FIG. 3, "ST" in FIG.
5 ”is converted into a frequency value.“ ST ”in FIG.
At 7 ", this value is multiplied by a coefficient, and at" ST8 "in FIG. 3, the calculation result is output as an odor concentration output signal.

Further, in "ST9" in FIG. 3, the odor concentration signal is logarithmically converted, and the result is further multiplied by ten.
In "ST10" in FIG. 3, the calculation result is output as an odor index signal.

FIG. 4 is a characteristic curve diagram when an odorous substance is measured using the sensor 1 in which the lipid film is attached to a quartz oscillator. In FIG. 4, the horizontal axis represents the concentration of an odorant, for example, amyl acetate in air, and the vertical axis represents the amount of change in the resonance frequency of the sensor 1.
In FIG. 4, "A" indicates the detection limit range of human odorous substances.

FIG. 4 shows that the concentration of the odorant in the air and the amount of change in the resonance frequency of the sensor 1 are proportional. Further, the proportional relationship is maintained within the detection limit range of the human odorous substance.

FIG. 5 shows an olfactory threshold which can be detected by humans.
FIG. 4 is a characteristic curve diagram showing a relationship between a detectable range of the sensor 1 and a distribution coefficient of the lipid membrane. In FIG. 5, the horizontal axis represents the threshold concentration of human, and the vertical axis represents the partition coefficient of the lipid membrane. Here, the partition coefficient of the lipid membrane is the ratio of the adsorption of odorous substances inside and outside the lipid membrane.

In FIG. 5, "a", "b", "c" and "d" are shown.
Shows the distribution of human olfactory threshold for citral, acetic acid, amyl acetate and ethanol, respectively,
“E” in FIG. 5 is a boundary line indicating the detectable range of the sensor 1.

From FIG. 5, it can be seen that the human olfactory threshold value and the detectable range of the sensor 1, that is, the minimum detection sensitivity of the sensor 1, match regardless of the odorant.

Here, the odor concentration is a dilution factor when the odor substance is diluted until the odor cannot be discriminated as described above, and is equivalent to a value obtained by dividing the odor substance concentration in the air by a human odor threshold. Therefore, the minimum detection sensitivity of the sensor 1 is equal to the human olfactory threshold regardless of the odorant, and the amount of change in the resonance frequency of the sensor 1 is proportional to the concentration of the odorant in the air. It can be seen that the frequency change is proportional to the odor concentration.

As a result, the odor concentration can be obtained by multiplying the change amount of the resonance frequency of the sensor 1 by, for example, the proportional coefficient by the multiplying circuit 8 in FIG.

Since the odor coefficient is generally defined by the following equation, odor index = 10 · log (odor concentration) (1) For example, the odor concentration is calculated by the logarithmic circuit 9 and the multiplication circuit 10 in FIG. Is logarithmically converted and the conversion result is multiplied by 10 to obtain an odor index.

It is to be noted that an odorless sample or the like may be actually detected using another sensor instead of the storage circuit 6 and measured and output by another counter.

Further, a frequency signal corresponding to the frequency in the case of no odor may be output by using a voltage controlled oscillation circuit or the like.

It is also possible to output only one of the odor concentration signal 104 and the odor index signal 105 without outputting both.

Further, since the proportionality coefficient varies depending on the thickness and type of the lipid membrane of each sensor, a more accurate measurement of the odor concentration and the like can be performed by obtaining a value for each sensor.

As described above with reference to FIG. 3, the timer circuit 4 can be omitted if this timer function is realized in the microprocessor 5.

The counter 3 can be omitted if the function of the counter can be realized in the microprocessor 5.

[0044]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. By applying a proportional coefficient to the frequency change amount of the sensor, an odor concentration meter capable of measuring the odor concentration with a simple configuration can be realized.

Further, by converting the odor concentration logarithmically and further multiplying it by ten, an odor concentration meter capable of measuring the odor index with a simple configuration can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing an embodiment of an odor concentration meter according to the present invention.

FIG. 2 is a functional block diagram illustrating arithmetic processing in terms of hardware.

FIG. 3 is a flowchart of a calculation process.

FIG. 4 is a characteristic curve diagram when an odorant is measured using the sensor 1.

FIG. 5 is a characteristic curve diagram showing a relationship between a smell threshold that can be detected by a human, a detectable range of a sensor, and a distribution coefficient of a lipid membrane.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor 2 Oscillation circuit 3 Counter 4 Timer circuit 5 Microprocessor 6 Storage circuit 7 Subtraction circuit 8, 10 Multiplication circuit 9 Logarithmic circuit 100, 101, 103 Control signal 102 Data signal 104 Odor concentration signal 105 Odor index signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-50637 (JP, A) JP-A-61-128138 (JP, A) JP-A-5-180746 (JP, A) JP-A-5-180746 99868 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 5/02 JICST file (JOIS)

Claims (2)

(57) [Claims] An odor concentration meter for measuring the concentration of an odorant, comprising: a sensor comprising a quartz oscillator or a surface acoustic wave element having an odor-sensitive film adhered to a surface thereof; An oscillation circuit that resonates, a counter that measures the oscillation frequency of the oscillation circuit, and a counter that is measured in advance from a measurement value output from the counter .
An odor concentration meter comprising: an arithmetic control unit for calculating an odor concentration by subtracting a measured value at the time of no odor and multiplying by a proportional coefficient. 2. An odor concentration meter according to claim 1, wherein said odor concentration meter for measuring the concentration of the odor substance comprises an arithmetic control means for calculating an odor index from the odor concentration.