JPH0634508A - Odor measurement device - Google Patents

Abstract

PURPOSE:To exactly measure odor density without any influence of drift of an odor sensor by making constitution capable of charging over from standard air to gas to be measure. CONSTITUTION:Gas to be measure collected with a gas measurement collector 1 is introduced to a standard air supply device 2 through a changing-over valve 4, odor substances are eliminated with the device 2 so as to become standard air, introduced to a measurement cell 3 through the valve 4 again and exhausted through a suction pump 7. In other words, a quartz oscillation type odor sensor 5 set in the cell 3 is exposed in the standard air and at the time a resonance frequency f0 is measured within a measurement circuit 6. Next, when the valve 4 is changed over, the gas to be measured supplied from the device 1 is introduced to the cell 3 without passing through the device 2 and at the time another resonance frequency f1 of the sensor 5 is also measured. The output DELTA f of the sensor 5 caused by odor components of the gas to be measured of both the outputs is given from DELTAf=f1-f0 and odor substance density can be exactly measured without any influence of drift of the odor sensor.

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 using an odor sensor such as a crystal oscillator type odor sensor, and more particularly to a device capable of stable measurement by eliminating the influence of baseline drift. Is.

[0002]

2. Description of the Related Art As a conventional odor measuring device, there is a device having a structure as shown in FIG. The device having the configuration shown in FIG. 3 uses a crystal oscillator as an odor sensor. This crystal oscillator is formed of, for example, an AT-cut crystal substrate, and a lipid bilayer film, which is an odor-sensitive film, is accumulated on the surface of the crystal oscillator via a metal electrode formed of gold or the like. In such a structure, odor molecules generally have a property of being easily adsorbed on a lipid membrane. When an odor substance in the air is adsorbed on the lipid bilayer of this odor sensor,
The amount of adsorption increases the mass of the film. Along with this, the resonance frequency of the crystal unit decreases. The odor can be measured by reading the change in the resonance frequency with a frequency counter.

[0003]

However, in the odor measuring device having the structure described in the above-mentioned prior art, the odor sensor (quartz oscillator) is simply left in the gas to be measured. In addition to temperature and humidity, this odor sensor drifts due to evaporation and oxidation of the substance of the odor sensitive membrane, so it is not possible to distinguish between the frequency change due to the drift of the odor sensor and the frequency change due to the adsorption of the odor substance. It has a drawback that it cannot measure a gradual change in concentration.

The present invention has been made in view of the above problems of the prior art, and by adopting a structure capable of switching between standard air and gas to be measured, the odor can be accurately measured without being affected by the drift of the odor sensor. It is intended to provide an odor measuring device capable of measuring a substance concentration.

[0005]

Means for Solving the Problems The structure of the present invention for solving the above-mentioned problems includes an odor sensor, a measuring circuit for measuring the output of the odor sensor, and a measuring cell in which the odor sensor is installed. A standard air supply device, a measured gas sampling device, a switching valve connected to the standard air supply device and the measured gas sampling device and introducing one of the gases into the measurement cell, and the measurement It is characterized in that it is configured to include a valve or a pump connected to the cell for maintaining a constant gas flow rate. Further, a crystal oscillator type odor sensor is used as the odor sensor. Further, as the standard air supply device, a deodorizing device which is connected to the measured gas sampling device and removes an odor substance from the measured gas is used.

[0006]

According to the present invention, the standard air and the gas to be measured can be switched, and the zero point can be measured immediately before the measurement of the gas to be measured, so that the influence of the drift of the baseline of the odor sensor is eliminated. It is possible to measure odor substances without receiving them.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the odor measuring device of the present invention. In FIG. 1, reference numeral 1 is a measured gas sampling apparatus, 2 is a standard air supply apparatus, and in the figure, a deodorizing apparatus that is connected to the measured gas sampling apparatus 2 and removes odorous substances from the measured gas is used. 3 is a measuring cell, 4 is a switching valve, which is connected to the measured gas sampling device 1 and the standard air supply device 2,
Either gas is selected and introduced into the measurement cell 3. 5
Is an odor sensor installed inside the measuring cell 3, and a crystal oscillator type odor sensor is used in the figure. Reference numeral 6 is a measuring circuit for measuring the change in the resonance frequency of the crystal oscillator type odor sensor 5, and reference numeral 7 is a suction pump for keeping the gas flow rate constant. Each device is connected by a pipe (double line in the figure) or a conducting wire (solid line in the figure).

In such a structure, at the start of measurement, the switching valve 4 is in the state of the valve position a shown in FIG. 2, and when the suction pump 7 is operated, the air flow shown by the arrow in FIG. 1 is generated. It occurs throughout the measuring device. At this time, the measured gas collected by the measured gas sampling device 1 is introduced into the standard air supply device 2 through the switching valve 4, and the standard air supply device 2 removes odorous substances to become standard air, It is introduced into the measuring cell 3 again through the switching valve 4,
Further, it is exhausted through the suction pump 7. That is, the crystal oscillator type odor sensor 5 installed in the measuring cell 3 is exposed to the standard air without odor, and the resonance frequency f ₀ at that time is measured by the measuring circuit 6.

Next, when the switching valve 4 is switched to the state of the valve position b shown in FIG. 2, the measured gas taken in from the measured gas sampling device 1 does not pass through the standard air supply device 2 and the measuring cell 3 The resonance frequency f ₁ of the crystal oscillator type odor sensor 5 at that time is similarly measured by the measuring circuit 6.

The output Δf of the crystal oscillator type odor sensor 5 due to the odor components in the gas to be measured having both outputs is given by Δf = f ₁ −f ₀ .

The measurement is always performed by the step response measurement, and since the zero point (f ₀ ) is measured immediately before the odor component measurement, it is not affected by the baseline drift.

As described above, according to the above-described embodiment, since the standard air and the gas to be measured can be switched, the zero point can be measured immediately before the measurement of the gas to be measured, and the baseline of the odor sensor can be measured. It is possible to measure odorous substances without being affected by drift. At the same time, since the suction pump for keeping the gas flow rate constant is used, the measurement can be performed without being affected by the gas flow rate fluctuation.

Although the crystal oscillator type odor sensor is used as the odor sensor in the above embodiment, the odor sensor is not limited to this, and an oxide semiconductor type odor sensor or the like may be used.

[0014]

As described above in detail with reference to the embodiments, according to the present invention, it is possible to realize an odor measuring device capable of accurately measuring the odor substance concentration without being affected by the drift of the odor sensor.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a switching state of a switching valve of the apparatus shown in FIG.

FIG. 3 is a configuration diagram showing an example of a conventional odor measuring device.

[Explanation of symbols]

 1 Measuring gas sampling device 2 Standard air supply device (deodorizing device) 3 Measuring cell 4 Switching valve 5 Crystal oscillator type odor sensor 6 Measuring circuit 7 Suction pump

Claims (3)

[Claims] 1. An odor sensor, a measurement circuit for measuring the output of the odor sensor, a measurement cell in which the odor sensor is installed, a standard air supply device, a measured gas sampling device, and the standard. A switching valve that is connected to the air supply device and the gas sampling device to be measured and selects one of the gases and introduces it into the measurement cell; and a valve or a pump that is connected to the measurement cell to keep the gas flow rate constant. An odor measuring device having a configuration provided with. 2. The odor measuring device according to claim 1, wherein a crystal oscillator type odor sensor is used as the odor sensor. 3. The odor measuring device according to claim 1, wherein the standard air supply device is a deodorizing device that is connected to the measurement gas sampling device and removes an odor substance from the measurement gas. measuring device.