JP2011174722A - Gas detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas detector including an electrochemical gas sensor, capable of acquiring at an early stage where gas concentration can be measured, after the application of power. <P>SOLUTION: The gas detector including an electrochemical gas sensor (hereafter, simply referred to as a "gas sensor") also includes an output correction mechanism having a function, wherein in a state where sensor output correction gas is introduced when starting the gas sensor, a sensor output value at an output correction object measurement time is predicted, by using some measuring time within a specific time range set as the output correction object measuring time, based on a sensor output value acquired actually by the gas sensor at each of two measurement times, selected within the specific time range in which the sensor output value is changed logarithmically with elapse of time; and the result is acquired as an output value for correction, and a sensor output acquired actually from the gas sensor at the output correction object measuring time is corrected, based on the output value for correction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas detector including a constant potential electrolytic oxygen sensor, for example.

For example, a certain type of constant potential electrolytic oxygen sensor has a gas permeable hydrophobic diaphragm that allows a gas to be detected to pass through a window that accommodates the electrolyte, and the electrolyte of the gas permeable hydrophobic diaphragm. And a counter electrode disposed at a certain distance from the working electrode. For example, the potentiostat causes the working electrode to have a constant potential at which oxygen reduction occurs. By being controlled, an electrolytic current flowing between the working electrode and the counter electrode corresponding to the concentration of oxygen gas is detected.
In such a constant potential electrolytic oxygen sensor, it is necessary to limit the amount of test gas supplied to the working electrode on the detection principle. For example, the test gas is supplied to the working electrode via a pinhole, for example. A structure having a structure for supplying is proposed (Japanese Patent Publication No. 61-56777).

Japanese Patent Publication No. 61-56777

  Thus, in the constant potential electrolytic oxygen sensor, for example, the atmosphere is introduced in a state where the supply amount is limited by turning on the power and starting energization to the constant potential electrolytic oxygen sensor. However, immediately after the start of energization, for example, the atmosphere existing around the working electrode in advance is supplied to the working electrode constituting the gas detection electrode, so that oxygen gas in the atmosphere reacts with the working electrode and the counter electrode and the working electrode. Electrolytic current flows between the two and the sensor output decreases rapidly, and then the amount of oxygen (oxygen gas) present around the working electrode in advance decreases over time, and the amount of oxygen supplied through the pinhole Since the amount of the atmosphere supplied to the working electrode is relatively decreased, the sensor output decreases with time, and after a predetermined time elapses, a constant output (for example, oxygen gas concentration in the atmosphere (21 The output value is stable at a sensor output at the time of starting the sensor (see FIG. 3), and therefore it takes time for the sensor output to stabilize. In the constant potential electrolytic oxygen sensor, the oxygen gas concentration measurement is actually performed after the sensor output is stabilized.

  Also, in other constant potential electrolytic gas sensors other than the constant potential electrolytic oxygen sensor, when the constant potential electrolytic gas sensor is in a non-energized state, the potential of the working electrode changes with the type of electrode constituent material over time. And a state in which equilibrium is reached at the natural electrode potential (equilibrium potential state) according to the combination of the type and concentration of the electrolyte, and this equilibrium potential state and measurement suitable for gas concentration measurement in a constant potential electrolytic gas sensor Since there is a difference in potential state, it takes time for the state at the interface between the working electrode and the electrolyte, for example, the state of ion density at the interface, to stabilize, after the power is turned on. The concentration cannot be measured.

  To solve such a problem, for example, in order to maintain a stable state at the interface between the working electrode and the electrolyte when the power of the constant potential electrolytic gas sensor is turned off, In order to keep the supply amount of oxygen supplied through the supply control means equal to the consumption amount of oxygen by the working electrode, a so-called “backup circuit” may be provided. This is not suitable for portable gas detectors, because it consumes a large amount of power, and is particularly unfavorable, especially in the case of a device equipped with a constant potential electrolytic oxygen sensor, because an electrode reaction always occurs. .

  The present invention has been made based on the above circumstances, and is a gas comprising an electrochemical gas sensor, which can quickly obtain a state in which gas concentration can be measured after power-on. The object is to provide a detector.

The gas detector of the present invention includes an electrochemical gas sensor, and an output correction mechanism that corrects a sensor output value from the electrochemical gas sensor acquired at the time of sequential measurement at regular time intervals when the electrochemical gas sensor is started up. With
For the electrochemical gas sensor, the sensor output initial fluctuation characteristic curve showing the change over time of the sensor output value acquired in the state where the sensor output correction gas is introduced at the time of sensor activation, the sensor output value is logarithmically with time. It has a logarithmic function region that changes functionally,
The output correction mechanism, at the time of measurement at any time within the time range corresponding to the logarithmic function region in the sensor output initial variation characteristic curve at the time of output correction target measurement, at the time of the output correction target measurement,
The output correction target measurement selected in a time range corresponding to a logarithmic function region in the sensor output initial fluctuation characteristic curve obtained in a state where a sensor output correction gas is introduced at the time of starting the electrochemical gas sensor Based on the sensor output value at each of the two measurements before the time, the sensor output value at the time of the output correction target measurement is predicted, and the predicted sensor output value is acquired as the correction output value. Processing and
It has a function of performing an output correction process for correcting the sensor output value from the electrochemical gas sensor actually acquired at the time of the output correction target measurement based on the correction output value acquired by the correction output acquisition process. It is characterized by.

  In the gas detector according to the present invention, when the output correction mechanism detects that the sensor output correction gas is introduced at the time of the output correction target measurement, the output correction target measurement time is the two measurements. It is updated as time of later measurement in time series of time, and it is configured to have a function to perform correction output acquisition processing and output correction processing at the time of the next output correction target measurement at the time of the output correction target measurement It is preferable.

Furthermore, in the gas detector of the present invention, an electrochemical oxygen sensor in which the gas to be inspected is supplied to the gas detection electrode via the gas supply restriction means is used as the electrochemical gas sensor. It is more preferable that the gas supply restriction unit is provided with a pinhole. And the gas detector of this invention can be set as the structure provided with the constant potential electrolytic oxygen sensor.
Furthermore, the gas detector of the present invention can be configured as a portable type.

According to the gas detector of the present invention, when an electrochemical gas sensor is started, the sensor output value during two measurements, which is actually acquired in a state where the sensor output correction gas is introduced, tends to change over time. The sensor output value predicted at the time of output correction target measurement is based on the actual sensor output initial fluctuation characteristic curve for the electrochemical gas sensor, and therefore the predicted sensor output value is used for correction. As the output value, the sensor output value actually obtained from the electrochemical gas sensor at the time of measurement of the output correction target is corrected by the correction output value, thereby compensating for the temporal change of the sensor output at the time of starting the electrochemical gas sensor. Therefore, after the power is turned on, the gas concentration can be measured and wait for the sensor output to stabilize. And no, it is possible to obtain an early stage.
Also, the configuration of the electrochemical gas sensor (gas detection electrode configuration, type of electrolyte, etc.), the length of the non-energization time (non-energized state) from when the power is turned off until the power is turned on again, and other conditions Regardless of whether or not sensor output values at the time of at least two measurements are acquired, a correction output value for correcting the sensor output value actually acquired from the electrochemical gas sensor at the time of output correction target measurement should be acquired. Therefore, high versatility can be obtained.
Furthermore, since a state in which the gas concentration can be measured can be obtained at an early stage after the power is turned on, it is extremely useful when configured as a portable type.

It is a block diagram which shows the outline of a structure of the principal part in an example of the gas detector of this invention. It is sectional drawing which shows the structure in an example of the constant potential electrolytic oxygen sensor which concerns on the electrochemical gas sensor which comprises the gas detector of this invention. It is a figure which shows the sensor output initial stage fluctuation characteristic curve about a constant potential electrolytic oxygen sensor. It is a figure which shows an example of the sensor output initial stage fluctuation characteristic curve for demonstrating the output correction operation | movement by the output correction mechanism in the gas detector of this invention. 6 is a graph showing the measurement results of oxygen gas concentration in Experimental Example 1. It is sectional drawing which shows the structure in the other example of the constant potential electrolytic oxygen sensor which concerns on the electrochemical gas sensor which comprises the gas detector of this invention.

Hereinafter, embodiments of the present invention will be described by taking, for example, a portable gas detector including a constant potential electrolytic oxygen sensor as an example.
FIG. 1 is a block diagram showing an outline of a configuration of a main part in an example of a gas detector of the present invention.
The gas detector includes, for example, a constant potential electrolytic oxygen sensor 10, a sensor control unit 30 that activates the constant potential electrolytic oxygen sensor 10 and outputs a gas detection signal from the constant potential electrolytic oxygen sensor 10, Main control means 40 for controlling the operation of the entire gas detector, storage means 50 for storing information relating to gas concentration measurement and output correction operation, and time measuring means for acquiring time information for performing the output correction operation described later 55, operating means (not shown) for setting the operation of the gas detector, display means (not shown) for displaying the type and concentration value of the detected gas, and the concentration of the detection target gas An alarm means (not shown) for issuing an alarm when it is detected that the reference value is exceeded, and a driving power source (not shown) made of a storage battery, for example, are provided.

FIG. 2 is a cross-sectional view schematically showing the configuration of an example of a constant potential electrolytic oxygen sensor according to the electrochemical gas sensor constituting the gas detector of the present invention.
This constant potential electrolytic oxygen sensor 10 has a pinhole 12 that constitutes a gas supply restricting means for introducing a gas to be inspected at one end while restricting the supply amount to the gas detection electrode, and at the other end a pressure adjusting opening. 13 is provided, and one end side gas permeable hydrophobicity made of a porous film such as a fluorine resin is formed on one end side inner surface of the casing 11 so that the pinhole 12 is closed from the inner surface side. On the other end side inner surface of the casing 11, the other end side gas permeable hydrophobicity made of a porous film such as a fluororesin is provided so that the diaphragm 15 is stretched and the pressure adjusting opening 13 is closed from the inner surface side. A diaphragm 16 is stretched, thereby forming an electrolyte chamber S in which an electrolyte made of, for example, an aqueous sulfuric acid solution is accommodated.
In the casing 11, a working electrode 20 constituting a gas detection electrode is provided on the surface (inner surface) on the liquid contact side of the one end side gas permeable hydrophobic diaphragm 15, and the counter electrode 21 is disposed on the other end side gas permeable hydrophobic diaphragm. 16 is provided on the liquid contact side surface (inner surface), and the reference electrode 22 is immersed in the electrolyte so as to face the working electrode 20 and the counter electrode 21 at positions spaced apart from each other. Is provided.

The working electrode 20 is formed, for example, by firing fine particles such as platinum, gold, ruthenium, palladium, or a mixture or alloy thereof together with a binder at a central position on one surface of the one-side gas-permeable hydrophobic diaphragm 15. An electrode catalyst layer is formed.
The counter electrode 21 is formed by, for example, firing fine particles of platinum, gold, ruthenium, palladium, or a mixture or alloy thereof together with a binder at a central position on one surface of the gas permeable hydrophobic diaphragm 16 at the other end. An electrode catalyst layer is formed.
The reference electrode 22 has a binder made of, for example, fine particles of platinum, gold, ruthenium, palladium, or a mixture or alloy thereof on the entire surface of a gas permeable base film made of, for example, a fluororesin porous film. An electrode catalyst layer formed by firing together is formed. The reference electrode 22 may have a configuration in which electrode catalyst layers are formed on both surfaces of a gas permeable base film, or may be configured by a single metal.

  In the case where the pinhole 12 has a uniform inner diameter, the inner diameter of the pinhole 12 in the casing 11 is practically 1.0 to 200 μm, for example, 80 μm. Moreover, the length of the pinhole 12 is 0.1 mm or more, for example.

  The sensor control unit 30 applies a voltage having a predetermined magnitude to the working electrode 20 so that a constant potential difference is generated between the working electrode 20 and the reference electrode 22. Here, the applied voltage to the working electrode 20 is such that the potential difference between the working electrode 20 and the reference electrode 22 is, for example, −2.0V to + 1.5V.

  The main control means 40 is acquired at the time of sequential measurement at regular time intervals at the time of starting the operation control mechanism for controlling the operation of the sensor control means 30 and other components and the constant potential electrolytic oxygen sensor 10. An output correction mechanism for correcting the sensor output value from the constant potential electrolytic oxygen sensor 10 and a gas concentration calculation mechanism having a function of calculating a gas concentration based on the correction sensor output value corrected by the output correction mechanism. I will.

  The information related to the gas concentration measurement recorded in the storage means 50 is, for example, specific to the constant potential electrolytic oxygen sensor 10 indicating the relationship between the sensor output value from the constant potential electrolytic oxygen sensor 10 and the gas concentration value. Individual calibration curve (sensitivity curve), zero calibration value, span calibration value, temperature correction data after calibration processing for constant potential electrolytic oxygen sensor 10 can be mentioned, and information related to output correction operation at sensor startup For example, a set value (t1 and t2) of time information at the time of measurement (elapsed time since the power is turned on and energization is started) in which the sensor output value is used in an output correction operation to be described later. be able to.

Hereinafter, the operation of the gas detector will be described.
In the gas detector, a predetermined voltage is applied between the working electrode 20 and the reference electrode 22 when a predetermined voltage is applied (energization is started) to the working electrode 20 based on the potential state of the reference electrode 22. In the measurement potential state, which is a state, a gas to be inspected such as air in the ambient atmosphere in the detection target space is supplied to the working electrode 20 through the pinhole 12 of the casing 11, thereby causing a gap between the working electrode 20 and the counter electrode 21. The value of the electrolysis current generated in the test gas is detected, and the concentration of oxygen gas in the test gas corresponding to the electrolysis current value is measured.

  Thus, as described above, the constant potential electrolytic oxygen sensor takes time for the sensor output to stabilize at the time of startup, and measures the oxygen concentration immediately after the gas detector is turned on. In the gas detector, when the gas detector is turned on and energization of the constant potential electrolytic oxygen sensor 10 is started, the sensor output correction gas is introduced. Then, an output correction operation for correcting the sensor output value from the constant potential electrolytic oxygen sensor 10 is performed. Hereinafter, the output correction operation will be specifically described.

For the constant potential electrolytic oxygen sensor 10, a sensor output initial fluctuation characteristic curve α showing a change over time of a sensor output value obtained in a state where, for example, the atmosphere that is a sensor output correction gas at the time of sensor activation is introduced, As shown in FIG. 3, the sensor output value suddenly decreases (rises) due to the start of energization of the constant potential electrolytic oxygen sensor 10, and then the sensor output value increases with time, and energization is started. After several minutes to several hours have elapsed, the output value is stabilized at a predetermined output value, for example, an output value having a magnitude corresponding to the oxygen concentration in the atmosphere.
Output ratio (%) of the sensor output value acquired when the atmosphere (sensor output correction gas) is introduced at the time of starting the sensor when the sensor output value when the oxygen concentration is 25% is 100% ) On the vertical axis and the elapsed time (sec) from the start of energization on the horizontal axis in the logarithmic coordinate system taken on a logarithmic scale, as shown by the broken line in FIG. Is a logarithmic function area LA that changes logarithmically with time, in other words, a sensor output initial fluctuation characteristic curve α having an area that can be linearly approximated in the logarithmic coordinate system. Here, the sensor output value is acquired, for example, every time interval of 1 second.
The logarithmic function region LA in the sensor output initial fluctuation characteristic curve α has a start time t0, an end time tn, and a length of time, for example, a configuration (specification) of the constant potential electrolysis oxygen sensor 10 and a length of non-energization time. For example, the elapsed time from the start of energization is at least 20 seconds or more and is within a time range of 240 seconds or less.

  In the gas detector, the output correction mechanism in the main control means 40 is used for any measurement within the time range (t0 to tn) corresponding to the logarithmic function region LA in the sensor output initial fluctuation characteristic curve (α). When the output correction target measurement is, the first measurement time t1 and the first measurement time selected before the output correction target measurement are selected within the time range corresponding to the logarithmic function region LA in the sensor output initial fluctuation characteristic curve (α). The sensor output value at the time of the output correction target measurement is predicted based on the sensor output value actually obtained from the constant potential electrolytic oxygen sensor 10 at each of the two measurement times t2 of the measurement time t2. Correction output acquisition processing for acquiring the sensor output value as a correction output value, and constant potential electrolytic oxygen during the output correction target measurement The output correction operation including the output correction process for correcting the sensor output value actually acquired from the sensor 10 based on the correction output value acquired by the correction output acquisition process is performed at the first measurement time t1 and the first time. The sensor output value from the constant potential electrolytic oxygen sensor 10 is recorded in the storage means 50 at each of the two measurement times t2.

Specifically, the correction output acquisition process by the output correction mechanism will be described. When the output correction target measurement is the next measurement time tm after the second measurement time t2, first, as shown in FIG. The tendency of the output change with time between the sensor output value (actual value) V1 at the first measurement time t1 and the sensor output value (actual value) V2 at the second measurement time t2 is detected, that is, 2 When the two sensor output values V1 and V2 are approximated by a logarithmic function (linear approximation in the logarithmic coordinate system), an approximate curve SL indicated by a solid line in FIG. 4 is acquired.
Here, both the sensor output value (actually measured value) V1 at the first measurement time t1 and the sensor output value (actually measured value) V2 at the second measurement time t2 are actually obtained from the constant potential electrolytic oxygen sensor 10. Is obtained by subtracting the reference sensor output value corresponding to the oxygen gas concentration present in the atmosphere, for example, 21%, from the sensor output value to be zero, and the sensor output value at the start of the constant potential electrolytic oxygen sensor 10 should be zero. This indicates the degree of deviation from a point.

  Next, the tendency of the output change over time between the sensor output value V2 at the second measurement time t2 and the sensor output value (on the sensor output initial fluctuation characteristic curve α) that should be originally at the output correction target measurement time tm is as follows: Based on the premise that the sensor output value V1 at the first measurement time t1 and the sensor output value V2 at the second measurement time t2 are the same as the tendency of the output change over time, the measurement subject to output correction is performed. The predicted sensor output value Vm at time tm is predicted by the approximate curve SL, and this sensor output value Vm should correct the sensor output value actually obtained from the constant electrolysis oxygen sensor 10 at the output correction target measurement time tm. Obtained as a correction output value Vm.

  The output correction process by the output correction mechanism will be specifically described. For example, the correction output is acquired from the sensor output value (actually measured value) actually acquired from the constant potential electrolytic oxygen sensor 10 at the output correction target measurement time tm. By subtracting the correction output value Vm acquired by the processing, the correction sensor output value at the output correction target measurement time tm is acquired.

  In the gas detector, the output correction operation including the correction output acquisition process and the output correction process is at least within a time range corresponding to the logarithmic function region LA in the sensor output initial fluctuation characteristic curve α, This is performed for sequential measurements after the measurement time t2 (during output correction target measurement).

  The oxygen concentration according to the correction sensor output value obtained by the output correction operation by the output correction mechanism by the gas concentration calculation mechanism in the main control means 40 is based on the individual calibration curve recorded in the storage means 50. Calculated. Here, at the time of output correction target measurement tm, when air in the environmental atmosphere (inspected gas) in the detection target space is introduced, the correction sensor output value acquired by the output correction operation as described above is This corresponds to the oxygen gas concentration in the test gas.

In the above output correction operation, since the first measurement time t1 is practically immediately after the start of energization of the constant potential electrolysis oxygen sensor 10, the degree of change (variation range) of the sensor output value with time is large. It is preferable to set the time (time) immediately before the time (for example, about 60 seconds) required for the initial process for the constant potential electrolysis oxygen sensor 10 after the power is turned on.
The second measurement time t2 can be set by selecting a specific time after the first measurement time t1, but the sensor output correction gas is introduced at the output correction target measurement time tm ( When the gas concentration instruction value calculated based on the correction sensor output value is substantially 0 ppm), the output correction target measurement time tm is updated and set as a new second measurement time. It is preferable in that the accuracy of correction can be improved.
In this case, the tendency of the output change with time between the sensor output value V1 (actually measured value) at the first measurement time t1 and the updated sensor output value (actually measured value) at the second measurement time. Is detected, and a new approximate curve is acquired. Based on this approximate curve, the constant potential electrolytic oxygen sensor 10 actually performs the output correction target measurement time t (m + 1) after the output correction target measurement time tm. A correction output value V (m + 1) for correcting the acquired sensor output value is acquired.

  The output correction operation at the time of starting the sensor as described above is based on the assumption that the calibration process of the constant potential electrolytic oxygen sensor 10 is properly performed, and the calibration process of the constant potential electrolytic oxygen sensor 10 itself is as follows. For example, it is performed once every predetermined period, for example, every six months.

Thus, in the gas detector including the constant potential electrolytic oxygen sensor in which the gas to be inspected is supplied to the working electrode constituting the gas detection electrode through the gas supply limiting means such as a pinhole, as described above. During the time until the sensor output value of the constant potential electrolytic oxygen sensor is stabilized, the oxygen gas concentration measurement cannot normally be performed with high reliability. After the charging, a state in which the gas concentration can be measured can be obtained at an early stage without waiting for stabilization of the sensor output value of the constant potential electrolytic oxygen sensor.
That is, the present inventors turn on the power of the gas detector in a state where, for example, the atmosphere (oxygen gas concentration is known), which is a sensor output correction gas, is introduced when the constant potential electrolytic oxygen sensor is started. The sensor output value of the constant potential electrolytic oxygen sensor does not change irregularly over time until the sensor output value stabilizes after the energization of the constant potential electrolytic oxygen sensor is started. Paying attention to the fact that the sensor output value has a logarithmic function region in which the sensor output value changes logarithmically with time in the sensor output initial fluctuation characteristic curve showing the change with time, i.e., the sensor output initial variation characteristic curve, As long as sensor output values at the time of two measurements selected within the time range corresponding to the logarithmic function region are obtained, the sensor output initial characteristic unique to the potentiostatic oxygen sensor is obtained. Even if the dynamic characteristic curve is not acquired in advance, the sensor output value at any measurement within the time range corresponding to the logarithmic function region can be predicted, and the predicted sensor output value is corrected. It was found that the gas concentration can be measured by correcting the sensor output value actually obtained from the constant potential electrolysis oxygen sensor based on the correction output value.

  Therefore, according to the gas detector having the above-described configuration, the sensor output initial fluctuation characteristic curve α is obtained by including the output correction mechanism having the function of performing the output correction operation including the correction output acquisition process and the output correction process. The second measurement time predicted based on the tendency of the output change over time between the first measurement time t1 and the second measurement time t2 selected within the time range corresponding to the logarithmic function area LA in FIG. Since the sensor output value at the time tm of the output correction target measurement after t2 is in accordance with the actual sensor output initial fluctuation characteristic curve α, the constant potential electrolysis type using the predicted sensor output value as a correction output value. By correcting the sensor output value actually obtained from the oxygen sensor 10 with the correction output value, the change over time of the sensor output at the time of starting the constant potential electrolytic oxygen sensor 10 is changed. A special arrangement including, for example, a backup circuit to keep the supply of oxygen supplied via the pinhole 12 and the consumption of oxygen by the working electrode 20 equal, for example As shown in the results of an experimental example to be described later, the state in which the concentration of oxygen gas can be measured after turning on the power is quickly determined without waiting for the sensor output to stabilize. Specifically, it can be obtained when the sensor output value V2 at the second measurement time t2 is acquired.

  Furthermore, the constant potential electrolytic oxygen sensor 10 usually has variations in sensitivity characteristics (individual differences), and the degree of change in sensor output over time at the time of sensor activation is not uniquely determined. When performing the output correction at the time of starting the sensor, for example, the sensor output initial fluctuation characteristic curve under various conditions for each constant potential electrolytic oxygen sensor is required. Regardless of the configuration (specifications) of the constant potential electrolysis oxygen sensor 10, the length of the non-energization time (non-energized state) from when the power is turned off to when the power is turned on again, and other conditions, the first As long as the sensor output values at the two measurement times t1 and the second measurement time t2 are acquired, the sensor output values are actually acquired from the constant potential electrolytic oxygen sensor 10 at the time of output correction target measurement. It is possible to obtain the correction output value to be corrected that the sensor output value, it is possible to obtain a high versatility.

  As described above, according to the present invention, for example, with respect to the constant potential electrolytic oxygen sensor 10, a state in which gas concentration measurement can be performed after power-on can be obtained at an early stage. The portable gas detector is extremely useful, and according to such a portable gas detector, the constant potential electrolytic oxygen sensor 10 can be measured for gas concentration when the sensor is activated. For example, when urgent gas detection is required, oxygen gas concentration can be detected at an early stage, for example, underground construction sites and tunnels. This is useful for preventing the occurrence of oxygen deficiency accidents in places where other people enter and work areas.

  Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.

<Experimental example 1>
In accordance with the configuration shown in FIG. 2, a constant potential electrolytic oxygen sensor according to the present invention having the following configuration was produced.
[Configuration of Constant Potential Electrolytic Oxygen Sensor (10)]
Casing pinhole (12); inner diameter is 80 μm, length is 1.5 mm,
Working electrode (20); outer diameter is 15 mm, thickness is 0.3 mm, electrode catalyst layer: formed by firing platinum fine particles together with binder, outer diameter is 10 mm,

  After performing a predetermined calibration process on the constant potential electrolytic oxygen sensor, the power is turned off and left for 24 hours, and then the power is turned on again in the atmosphere to supply the working electrode and the reference electrode. A voltage with a magnitude of −600 mV is applied to the working electrode and energized. The time when 40 seconds have elapsed from the start of energization is the first measurement (t1), and 60 seconds from the energization start. The time at which the lapse of time was taken as the second measurement time (t2), and the oxygen gas concentration was measured while performing the output correction operation. The results are shown in FIG. 5 (curve (β)).

In FIG. 5, the vertical axis represents the oxygen gas concentration instruction value (%), the horizontal axis represents the elapsed time (sec) after the power is turned on again, and the curve (α) indicated by the broken line is It is a time-dependent change characteristic curve of the actual gas concentration instruction | indication value about the said constant potential electrolytic oxygen sensor when an output correction operation is not performed.
In the curve (β) in FIG. 5, the plot (square mark) at the time of the measurement before the first measurement (t1) is the sensor output value at the time of the first measurement (t1) and at the time of the second measurement. The sensor output actually obtained based on the output value for correction is set as the output value for correction based on the approximated curve obtained by approximating the sensor output value at (t2) with a logarithmic function. The gas concentration instruction value corresponding to the corrected sensor output value obtained by correcting the value is shown, and between the sensor output value at the first measurement (t1) and the sensor output value at the second measurement (t2). Plots (squares) at the time of measurement within the time range of the sensor output value actually obtained based on the output value for correction using the sensor output value interpolated based on the approximate curve as the output value for correction. Obtained by correcting The shows a correction sensor output value correction sensor output value gas concentration indication value corresponding to that based on the correction output prediction value corresponding to.

  As is clear from the above results, the sensor output values over time output at the time of the first measurement and at the time of the second measurement, which are acquired in the state in which the atmosphere (gas for output correction) is introduced when the sensor is activated. Based on the tendency of the change, the sensor output value at the time of the output correction target measurement after the second measurement time is predicted, and the predicted sensor output value is obtained as the correction output value. According to the gas concentration measuring method according to the present invention in which the sensor output value actually obtained from the electrolyzed oxygen sensor is corrected by the correction output value and the gas concentration is measured, the gas concentration indication value is reapplied by the power supply. For example, after 40 seconds have passed since the energization of the constant potential electrolytic oxygen sensor is started, the gas concentration indication value is stable within a range of ± 5%, for example, and the power is turned on. , The early state that can perform gas concentration measurement, in these examples, for example, when the sensor output value at the time of the second measurement is obtained, it is confirmed that it is possible to obtain.

As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be added.
For example, according to the present invention, the sensor output initial fluctuation characteristic unique to the potentiostatic gas sensor is used in the first measurement time (t1) and the second measurement time (t2) selected when the output correction operation is performed at the time of starting the sensor. There is no particular limitation as long as it is set within a time range corresponding to the logarithmic function region in the curve.
Furthermore, the output correction mechanism updates the latest measurement time as a new second measurement time each time the output correction operation is performed, and outputs the sensor output at each of the first measurement time and the latest measurement time. It may be configured to have a function of acquiring a predicted output value for correction at the time of subsequent measurement based on a change in output with time.
Furthermore, the output correction operation at the time of starting the sensor is performed for a fixed time after the power is turned on, but the subsequent output correction may be performed by switching to a method of tracking the zero point. Good.

  In the case where the gas detector of the present invention has a configuration including a constant potential electrolytic oxygen sensor, the constant potential electrolytic oxygen sensor is not limited to the above configuration, and for example, as shown in FIG. The thing of such a structure can be used.

FIG. 6 is a cross-sectional view showing a configuration in another example of a potentiostatic oxygen sensor according to an electrochemical gas sensor constituting the gas detector of the present invention.
This constant potential electrolytic oxygen sensor 10 includes a casing 61 having a substantially box shape as a whole, having an electrolytic solution chamber S in which an electrolytic solution is accommodated. Reference numeral 62 denotes a gas permeable hydrophobic pressure adjusting membrane made of, for example, a fluorine resin.
In the casing 61, at a position aligned with the electrolytic solution chamber S, there is a sensitive portion forming space 65 composed of a substantially cylindrical through-hole extending in the vertical direction communicating with the internal space of the electrolytic solution chamber S through the communication hole 63. On the upper surface side of the upper surface side protection plate 70 formed in the sensitive portion forming space 65 and formed with a plurality of through holes 70A each penetrating in the thickness direction, for example, filter paper A plate-like lid member (gas supply limiting member) 80 made of, for example, a liquid crystal polymer, which is formed by penetrating an electrolyte solution holding layer (not shown), a working electrode 75, and a pinhole 81 for introducing a gas to be inspected is sequentially formed. It is housed and arranged.
A reference electrode 76 is provided at a central position on the lower surface side of the upper surface side protection plate 70 with an electrolyte solution holding layer (not shown) made of, for example, filter paper interposed.
In addition, a lower surface side protection plate 85 in which a fluid flow path formed of a plurality of through holes 85A each penetrating in the thickness direction is disposed below the upper surface side protection plate 70 in the sensitive portion forming space 65. The cap member 90 in which an electrolyte holding layer (not shown) made of, for example, filter paper, a counter electrode 77, and a gas discharge through-hole 90A for discharging the gas to be inspected are sequentially formed on the lower surface side of the lower surface protection plate 85. It is housed and arranged.

  The working electrode 75 in this constant potential electrolytic oxygen sensor has, for example, platinum, gold, or the like at a central position on one surface of a gas permeable base film made of, for example, a porous film of a fluorine resin having air permeability and water repellency. An electrode catalyst layer is formed by firing fine particles of ruthenium, palladium, or a mixture or alloy thereof together with a binder. Further, the counter electrode 77 has fine particles such as platinum, gold, ruthenium, palladium, or the like at a central position on one surface of a gas permeable base film made of a porous film of a fluororesin having air permeability and water repellency. An electrode catalyst layer formed by firing a mixture or alloy of the above together with a binder is formed.

Even in such a configuration, the sensor output initial fluctuation characteristic curve showing the change over time of the sensor output value acquired in the state where the sensor output correction gas, for example, the atmosphere, is introduced when the sensor is activated is shown in FIG. A tendency similar to that of the constant potential electrolytic oxygen sensor having the configuration shown in FIG. 1, that is, a logarithmic function area LA in which the sensor output value changes logarithmically with time, in other words, an area that can be linearly approximated in the logarithmic coordinate system. Have.
Therefore, the output correction operation including the correction output acquisition process and the output correction process described above is performed by the output correction mechanism, so that after the power is turned on, the gas concentration can be measured and the sensor output is stabilized. And can be obtained early.

Furthermore, the electrochemical oxygen sensor used in the present invention is not limited to a constant potential electrolytic oxygen sensor. For example, a gas to be inspected that is diffusion-limited by a gas supply limiting means using a pinhole is used, for example, from a noble metal. A galvanic cell for detecting the oxygen concentration in the gas to be inspected based on the current value generated by the reduction reaction at the cathode and the oxidation reaction at the anode made of, for example, lead arranged via the cathode and the electrolyte For example, a gas to be inspected that is diffusion-limited by a gas supply restricting means using a pinhole is applied to one of the electrodes (cathodes) of a pair of electrodes provided on each of the upper and lower surfaces of the oxygen sensor or the zirconia solid electrolyte. Supply and detect the oxygen concentration in the test gas based on the current value (limit current value) obtained within a certain applied voltage range Or the like can be used field current type zirconia oxygen sensor.
Even in such an electrochemical oxygen sensor, the sensor output initial variation characteristic curve showing the change over time of the sensor output value acquired in the state where the sensor output correction gas, for example, the atmosphere is introduced when the sensor is started is shown in FIG. 2 is a logarithmic function area LA in which the sensor output value changes logarithmically with time, in other words, an area that can be linearly approximated in a logarithmic coordinate system. The output correction operation including the correction output acquisition process and the output correction process described above is performed by the output correction mechanism, so that the gas concentration measurement can be performed after the power is turned on. It can be obtained early without waiting for stabilization.

  Furthermore, in the electrochemical oxygen sensor, the gas supply limiting means for supplying the diffusion-controlled gas to be inspected to the gas detection electrode is not limited to a pinhole, for example, a porous film, It may be a non-porous film such as a plastic film.

Furthermore, the present invention is not limited to an electrochemical oxygen sensor. For example, carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen monoxide, nitrogen dioxide, ozone, phosgene, AsH ₃ , PH ₃ , SiH ₄ , B ₂ H ₆ , GeH ₄ , HCl, CCl ₄ , HF and the like can also be applied to electrochemical gas sensors.

DESCRIPTION OF SYMBOLS 10 Constant potential electrolytic oxygen sensor 11 Casing 12 Pinhole 13 Pressure adjustment opening 15 One end side gas permeable hydrophobic diaphragm 16 Other end side gas permeable hydrophobic diaphragm S Electrolyte chamber 20 Working electrode 21 Counter electrode 22 Reference electrode 30 Sensor control means 40 Main control means 50 Storage means 55 Timekeeping means 61 Casing 62 Gas permeable hydrophobic pressure adjusting membrane 63 Communication hole 65 Sensitive part forming space 70 Upper surface side protection plate 70A Through hole 75 Working electrode 76 Reference electrode 77 Counter electrode 80 Plate-shaped lid member (Gas supply restriction member)
81 Pinhole 85 Lower surface side protective plate 85A Through hole 90 Cap member 90A Gas exhaust through hole

Claims (6)

Comprising an electrochemical gas sensor and an output correction mechanism for correcting the sensor output value from the electrochemical gas sensor acquired at the time of sequential measurement at predetermined time intervals when the electrochemical gas sensor is started,
For the electrochemical gas sensor, the sensor output initial fluctuation characteristic curve showing the change over time of the sensor output value acquired in the state where the sensor output correction gas is introduced at the time of sensor activation, the sensor output value is logarithmically with time. It has a logarithmic function region that changes functionally,
The output correction mechanism, at the time of measurement at any time within the time range corresponding to the logarithmic function region in the sensor output initial variation characteristic curve at the time of output correction target measurement, at the time of the output correction target measurement,
The output correction target measurement selected in a time range corresponding to a logarithmic function region in the sensor output initial fluctuation characteristic curve obtained in a state where a sensor output correction gas is introduced at the time of starting the electrochemical gas sensor Based on the sensor output value at each of the two measurements before the time, the sensor output value at the time of the output correction target measurement is predicted, and the predicted sensor output value is acquired as the correction output value. Processing and
It has a function of performing an output correction process for correcting the sensor output value from the electrochemical gas sensor actually acquired at the time of the output correction target measurement based on the correction output value acquired by the correction output acquisition process. Gas detector characterized by.   When the output correction mechanism detects that the sensor output correction gas has been introduced at the time of the output correction target measurement, the output correction mechanism measures the output correction target measurement time-sequentially of the two measurement times. 2. The gas detector according to claim 1, wherein the gas detector has a function of performing update output acquisition processing and output correction processing at the time of the next output correction target measurement at the time of the output correction target measurement. .   3. The gas detector according to claim 1, wherein the electrochemical gas sensor is an electrochemical oxygen sensor in which a gas to be inspected is supplied to a gas detection electrode through a gas supply restriction unit.   The gas detector according to claim 3, wherein the gas supply restriction means has a pinhole formed therein.   The gas detector according to claim 3 or 4, wherein the electrochemical gas sensor is a constant potential electrolytic oxygen sensor.   The gas detector according to any one of claims 1 to 5, wherein the gas detector is configured as a portable type.

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