JP3882297B2 - Gas measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas measuring device, and more particularly to a gas measuring device that measures gas components and odor components using a sensor using a conductive polymer film.
[0002]
[Prior art]
Performing qualitative and quantitative measurement of gas using gas sensors (including odor sensors) that react to various gases has been put into practical use. For example, what is called an artificial nose using an odor sensor may be applied to a fire alarm by detecting the quality of foods and fragrances, odor pollution quantitative standards, and burning odor detection using an odor detection system. Furthermore, it is expected that it can be used for tracking, identification, authentication, and drug testing of humans if it is comparable to a dog's nose by increasing sensitivity.
[0003]
One that has already been put into practical use as a gas sensor or an odor sensor uses a conductive polymer represented by polypyrrole as a sensitive film.
[0004]
This is to electrically measure a change in resistance value of the sensor caused by a gas component contained in the air adhering to the sensitive surface of the sensor. With this sensor, analysis can be performed while the sensitive film is maintained at room temperature. In addition, in sensors using conductive polymers, not only changes in electrical characteristics due to the interaction between gas components and conductive polymers, but also gas components and dopants (added to increase the conductivity of conductive polymers) Changes in electrical characteristics due to the interaction with the material), it is possible to make sensors with different detection sensitivities and characteristics by appropriately selecting conductive polymers and dopants. The substance of the component can be detected.
[0005]
[Problems to be solved by the invention]
In a gas sensor using a conductive polymer film, electrical characteristics such as electrical conductivity and electrical resistance of the conductive polymer film change as the sample is adsorbed and desorbed. As the conductive polymer film repeats the sample measurement, the electrical characteristics of the film irreversibly change, and the difference from the electrical characteristics exhibited by the film at the beginning of use increases over time. is there. When this difference is increased, the noise component included in the measurement result is increased, and not only measurement reproducibility is deteriorated, but also gas responsiveness of the sensor is deteriorated. Therefore, it is necessary to keep the electrical characteristics of the sensor within a certain range in order to maintain the continuity of the gas measuring device using the sensor using the conductive polymer film. And when it exceeds a certain range, it is necessary to replace the sensor with a new one.
[0006]
However, since the sensor replacement time varies depending on the type of polymer conductive film and the usage environment, conventionally, the measurer manages the sensor replacement time by monitoring the electrical characteristics (mainly the resistance value) of the sensor, Alternatively, when the measurement result of the sample specimen is analyzed, the sensor is exchanged when a defect such as, for example, a decrease in identification ability is felt. For this reason, there is a problem that the measurer is burdened with the management of the replacement time, and the operator is not aware of the replacement time coming.
[0007]
In view of the above, an object of the present invention is to provide a gas analyzer capable of solving such a problem and automatically determining and informing a sensor replacement time.
[0008]
[Means for Solving the Problems]
The gas measuring apparatus of the present invention made to solve the above problem is a gas using at least one sensor that utilizes the fact that the electrical properties of the film change due to the adsorption of the gas component to the conductive polymer film. In the measurement apparatus, initial electrical property storage means for storing electrical properties of the polymer film in an initial stage of sensor use, temporal change measurement means for periodically measuring electrical properties of the polymer film, and temporal change measurement means Determining means for determining the replacement time of the sensor from the calculation result using the current electrical characteristics measured by the sensor and the electrical characteristics stored in the initial electrical characteristics storage means, and notifying means for notifying the sensor deterioration by a signal from the determining means It is characterized by comprising.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The gas measuring device of the present invention measures and stores the electrical characteristic value at the initial stage of use of the sensor, and allows an acceptable electrical characteristic resistance value based on an increase in noise component expected due to a change with time of the electrical characteristic value of the sensor Determine the amount of deviation (ratio). The gas measuring device continuously measures the electrical characteristic value of the sensor at a timing specified in advance, and compares the current electrical characteristic value with the allowable deviation amount to determine whether the allowable range is exceeded. When the allowable range is exceeded, the notification means notifies that the sensor replacement time has come.
[0010]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a gas measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the gas measuring apparatus.
[0011]
In the figure, reference numeral 1 denotes a gas sensor unit, which is configured by forming a conductive polymer film using polypyrrole between two electrodes. In this gas sensor unit, when a gas component adheres to the conductive polymer film, the resistance value, which is one of the electrical characteristics, changes. Therefore, the gas can be detected by measuring the resistance value between the electrodes. Note that the gas sensor unit 1 may be made up of a plurality of sensors having different types and addition amounts of dopants so as to be sensitive to various gases. Reference numeral 2 denotes a control unit, which is configured by a computer. 3 is a notification means, and an alarm is used. In addition, the CRT screen can be used as a notification means by issuing a message prompting that it is time to replace it on the CRT screen of the computer as necessary.
[0012]
The control unit 2 includes a time-change measuring unit 21, an initial electrical characteristic storage unit 22, and a determination unit 23. The temporal change measuring means 21 monitors the resistance value of the sensor at predetermined time intervals. The initial electrical characteristic storage means 22 stores the resistance value of the gas sensor unit 1 immediately after the new gas sensor unit is attached. This storage may be performed by allowing the measurer to input by inputting from the keyboard, and when the gas sensor is replaced with a new gas sensor, the apparatus automatically stores the first measured value after the start of the measurement. It can also be. The determination means 23 performs an operation for comparing the current resistance value sent from the time-varying measurement means 21 with a reference value obtained from the resistance value data stored in the initial characteristic storage means 22, and When the value is exceeded, a signal is sent to the alarm 3. The alarm device that has received the signal notifies the measurer that it is time to replace it.
[0013]
Next, operation | movement of this measuring apparatus is demonstrated using a flowchart. In this gas measuring device, before starting the measurement of the day, the sensor is replaced when the amount of change from the electric resistance value at the initial stage of use of the sensor exceeds 80%. Therefore, the following operation is performed.
[0014]
After starting the gas measurement device (st1), after waiting for a certain time to stabilize the device (st2), the current resistance value of the gas sensor unit 1 is monitored (st3), and the following equation is calculated. The initial resistance value is stored in advance in the control unit as described above.
[0015]
(Initial resistance value−current resistance value) / initial resistance value (1) The value of equation (1) (deviation ratio of sensor resistance value) is compared with the allowable deviation ratio (st4). Then, it is determined whether or not the deviation ratio is within the allowable range (for example, within ± 80% of the initial resistance value) (st5). If the deviation ratio is within the allowable range, the measurement process is continued (st6). If the allowable range is exceeded, the alarm 3 is activated to urge that the sensor replacement time has come (st7). Then, the measurer determines whether or not to continue the measurement in response to the alarm from the alarm (st8), and when the measurement continuation command is input, the measurement process is continued. If not, replace the sensor. An input to the effect is performed and the exchange process is performed (st9).
[0016]
In addition, when multiple sensors are used, the replacement time is notified when even one of the sensors exceeds the allowable range. However, depending on the case, the change with time of only a specific sensor among the multiple sensors is monitored. However, the notification may not be made until this specific sensor is time for replacement.
[0017]
In addition, it is not a comparison of the resistance value of the sensor membrane, but the capacitance (C), inductance (L), electrical conductivity (σ), etc., which are electrical characteristics other than the resistance value of the conductive polymer membrane sensor, are out of a certain range. Therefore, the sensor replacement time may be determined.
[0018]
In addition, the measurement of the electrical characteristics (resistance value, etc.) in the present invention is not limited to the direct measurement of the electrical characteristics of the sensitive film, but the balance resistance and sensor resistance value required for driving the conductive polymer film. Such a difference is also included in the case of comparing the deviations because it is substantially equivalent to measuring the electrical characteristics of the sensitive film.
[0019]
Hereinafter, embodiments of the present invention will be summarized.
(1) In the gas measuring apparatus using at least one sensor utilizing the fact that the electrical characteristics of the film are changed by adsorbing a gas component to the conductive polymer film, the polymer film in the initial stage of using the sensor. Initial electrical characteristic storage means for storing the electrical characteristics of the polymer film, temporal change measurement means for periodically measuring the electrical characteristics of the polymer film, current electrical characteristics measured by the temporal change measurement means, and initial electrical characteristic storage means Determining means for determining the replacement time of the sensor based on whether the difference from the stored electrical characteristics is a certain ratio or more with respect to the initial electrical characteristics; and notifying means for notifying sensor deterioration by a signal from the determining means. A gas measuring device characterized by that.
(2) Use of a specific sensor among the sensors in a gas measuring device using at least two or more sensors utilizing the fact that the electrical properties of the film change due to adsorption of gas components to the conductive polymer film Initial electrical characteristic storage means for storing electrical characteristics in the initial stage of the present invention, time-dependent change measuring means for periodically measuring the electrical characteristics of the polymer film of the specific sensor, and current electrical characteristics measured by the time-dependent change measuring means And a determination means for determining a sensor replacement time from a calculation result using the electrical characteristics stored in the initial electrical characteristic storage means, and a notification means for notifying the sensor deterioration by a signal from the determination means. Gas measuring device.
[0020]
【The invention's effect】
As described above, in the gas measuring device of the present invention, since the sensor replacement time can be automatically determined, anyone can use it and the management of the replacement time is simple. Further, since the reference value of the sensor replacement time can be set to the accuracy expected by the measurer, the replacement time can be adjusted according to the required measurement accuracy, and excessive replacement can be prevented. Furthermore, the measurer can be engaged in peace of mind without worrying about measurement errors due to sensor deterioration.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a gas measuring apparatus showing an embodiment of the present invention.
FIG. 2 is an operation flow diagram of a gas measuring apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1: Gas sensor unit 2: Computer (CPU)
3: Notification means 21: Temporal change measurement means 22: Initial electrical characteristic storage means 23: Determination means

Claims (1)

In a gas measuring apparatus using at least one sensor that utilizes the fact that the electrical properties of the film change due to adsorption of gas components to the conductive polymer film,
Initial electrical property storage means for storing electrical properties of the polymer film in an initial stage of sensor use;
A time-change measuring means for periodically measuring electrical characteristics of the polymer film;
A determination means for determining the replacement time of the sensor from a calculation result using the current electrical characteristics measured by the time-change measuring means and the electrical characteristics stored in the initial electrical characteristics storage means;
A gas measuring device comprising: notifying means for notifying sensor deterioration by a signal from the determining means.

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