JPS59192953A - Oxygen gas concentration analyzer - Google Patents

Abstract

PURPOSE:To enable easy measurement of concn. of gaseous oxygen with high accuracy by providing prescribed electrodes and a diffusing hole to a box body formed with an oxygen ion permeating body consisting of a solid electrolyte and specifying the size of the diffusing hole. CONSTITUTION:An oxygen ion permeating body 1 consisting of a solid electrolyte is formed in a part on the side wall of a box body 40, and a cathode 2 is attached on the inside wall surface thereof and an anode 3 on the outside wall surface. A diffusing hole 5 for diffusing oxygen is opened in the body 40 and the aperture area thereof is made <=0.5 the area of the cathode. The diameter of the hole is made >=0.05mm. and the length thereof <=20mm.. This sensor B is mounted in a measuring cell 10, in an actual device. The measuring gas heated to 600-1,000 deg.C is introduced into the sensor through the hole 5 and when the voltage impressed on the electrodes is increased, the current is increased and therefore the concn. of oxygen is measured from the limiting current value thereof. The easy measurement with high acculacy is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen gas concentration analyzer using a solid electrolyte body.

Conventionally, zirconia oxygen concentration cells have been generally used to measure oxygen concentration in gas.

This measuring device consists of electrodes made of platinum or the like formed on both sides of a zirconia plate, which is a solid electrolyte.

To measure oxygen concentration using this device, one electrode is contacted with the scum to be measured and the other electrode is contacted with a reference gas containing oxygen of known concentration at a high temperature of 650 to 900C, and the 9 electrodes are placed in contact with each other. By measuring the electromotive force generated, the oxygen concentration in the waste to be measured is measured. however.

Since this device attempts to utilize the electromotive force determined by the oxygen partial pressure ratio of two oxygen systems (oxygen in the gas to be measured and oxygen as the reference gas) and temperature, the oxygen partial pressure in the gas to be measured is If the partial pressure of oxygen is close to that of the reference gas, only a small electromotive force can be obtained, and a daytime-sensitive instrument is required. The equipment is complicated because a reference gas is required.

The present invention aims to provide an oxygen gas concentration analyzer free from such drawbacks.

That is, one aspect of the present invention is as illustrated in FIG.

A box 40 in which at least a portion of the side wall constituting a closed space is formed of an oxygen ion permeable body 1 made of a solid electrolyte, a cathode 2 provided on the inner wall surface of the oxygen ion permeable body 1, and the cathode provided on the outer wall surface thereof. An electrode consisting of an anode 6 provided opposite to the electrode 2, and both of the electrodes 2 and 6
A power source 7 and 9 configured to apply a voltage between the two electrodes 2,
The box 40 has an ammeter 9 configured to measure the current flowing between the voltages 5 and 5, and a space chamber 6 inside the box 40 by diffusion of a smaller amount of oxygen than the oxygen delivery capacity of the voltage. A diffusion hole 5 is provided, and the ratio of the area of the opening of the diffusion hole to the surface area of the cathode is 0.
5 or less, the hole diameter is 0.05 mm or more, and the hole length is 20 mm or less.

When measuring the oxygen concentration in a gas using the device of the present invention, a detection section consisting of a box having an oxygen ion permeable body and a diffusion hole, and negative and negative electrodes formed on both sides of the oxygen ion permeable body (hereinafter referred to as a sensor, as shown in Figure 2) is placed in a gas to be measured at a high temperature of 600 to 1000°C, and the voltage applied between the negative and positive electrodes is gradually increased by the power source. I'm going to go. As the voltage increases, the current flowing between the electrodes initially also increases, but above a certain voltage, the current value is maintained at a constant value. This constant current value is the limiting current value, and by measuring the limiting current value, the oxygen concentration in the gas to be measured can be measured.

This point will be explained in detail below. First, during the above measurement operation, oxygen in the gas to be measured diffuses through the diffusion hole and enters the empty chamber inside the box, is reduced to oxygen ions at the cathode, and passes through an oxygen ion permeable body made of a solid electrolyte. and sent to the anode.

It is oxidized to oxygen again at the anode and discharged to the outside of the box. In other words, the oxygen gas that entered the box is yin and yang WJ.
It is sent to the outside by the oxygen sending action (oxygen pumping action) by the electrolyte. This action selectively exhausts only oxygen in the opposite direction to the flowing current, and the amount of exhaust per unit time is proportional to the passed current. What is important in the present invention is that the cathode for reducing oxygen ions in the oxygen delivery action is provided inside the perforated box, so that the oxygen supplied to the cathode is Oxygen is supplied from the outside through the holes, and the inflow of oxygen is suppressed at the diffusion holes. As a result, the oxygen concentration within itself is lower than that in the outside air (measured gas). At the same time, a certain oxygen concentration difference also occurs because oxygen passes through the cathode and reaches the solid electrolyte. This is called concentration polarization of the electrode.

Oxygen is supplied from the outside air to the space chamber inside the box.

is carried out by the diffusion of oxygen in the gas through the diffusion pores,
The supply amount Q per second is approximately here, D is the diffusion coefficient of oxygen in the gas, S is the area of the opening of the diffusion hole, l is the depth of the diffusion hole, and △P is the oxygen partial pressure of the outside air and the box. The difference between the partial pressure of oxygen in the space chamber inside the body, N is the gas 1i
It is the total number of moles of oxygen and other gas molecules contained in it. The amount of oxygen flowing into the case from the outside air through the diffusion holes is maximum when the oxygen partial pressure in the space inside the case becomes 0 (zero). Let Il be the current corresponding to Q at that time, 4FI) SN and I β −□・PO2・・・・・・・・・
(1) is almost like a hailstorm. Here, PO2 is the oxygen concentration of outside air. Also, if the total pressure of the gas is constant, N is a function only of temperature. The diffusion coefficient of oxygen in a gas is a function of temperature and oxygen concentration in the gas.

Although the values differ depending on the type of gas, these values are determined once the gas system (components in the gas) is determined.

Furthermore, since oxygen actually reaches the solid electrolyte through the cathode, a certain oxygen concentration difference is required inside the cathode, and therefore the oxygen concentration in the space inside the box does not become zero. t/-1t, area s-1 of the opening of the diffusion hole rE
If the area A is made sufficiently smaller than the area A, the difference in oxygen concentration due to concentration polarization of the electrodes can be made much smaller than the difference in oxygen concentration between the inside of the box and the outside air caused by the diffusion holes. The maximum value of the ratio between the area of the diffusion hole and the area of the cathode that satisfies this condition is limited by the current carrying capacity of the electrode. Therefore, under the above conditions, the oxygen concentration in the space inside the box is extremely lower than the oxygen concentration in the outside air, and at this time, the relationship between the limiting current flowing between the electrodes and the oxygen concentration is almost the same as described in (1) above. It will be hailed in a ceremony. Therefore, from the limiting current value (Jl), the unknown oxygen concentration in the gas to be measured (Po2)
can be found.

The magnitude of the limiting current value (Ig) is measured as follows. The relationship between the applied voltage applied between the electrodes and the current flowing between the electrodes is as shown in the curve shown in FIG. Here, the sensor is kept at a certain temperature. Apply voltage to O
When the voltage increases steadily from 0 to VAO, the current increases linearly with the voltage, but VA
Above this value, the slope becomes gentle, and below vB, even if the voltage is increased, the current hardly increases. This phenomenon occurs because the oxygen concentration in the space inside the box becomes almost O due to the effect of the diffusion holes, and the current flowing between the electrodes is restricted. Therefore, the saturation current value in FIG. 7 becomes the limit current value (1β).

From equation (1), PO□ is.

PO4-resistant-・Il...(2), and the proportionality constant 174F08N can be changed depending on the area S of the opening of the diffusion hole and its depth L, so it depends on the oxygen concentration range to be measured. The size of II can be selected to be the optimal value. As a result, the oxygen concentration ranges from very small to several tens of percent.
It becomes possible to easily measure up to high concentrations. As explained in FIG. 7, II is determined by gradually increasing the voltage applied between the electrodes. Alternatively, it may be determined by applying a certain constant voltage determined by the measured oxygen concentration range between the electrodes and measuring the current flowing at that time. In this case, the scale of the ammeter can be scaled almost proportionally to the oxygen concentration.

As is known from the above, in one aspect of the present invention.

The amount of oxygen that passes through the electrode is set to be the same as the amount of oxygen absorbed by the diffusion holes provided in the box, and in other words, the amount of oxygen sent out by the electrode is dependent on ``diffusion rate limiting by the diffusion holes'', thereby reducing the amount of oxygen that passes through the box. Its distinctive feature is that it attempts to measure the concentration of oxygen in a gas to be measured outside the body.

Therefore, according to the present invention, since the device of the present invention applies a voltage between the electrodes and utilizes the limiting current flowing between the two electrodes, it utilizes the electromotive force generated between the electrodes as described above. Compared to concentration batteries.

Can be easily measured. This is particularly effective when the oxygen concentration in the gas to be measured is high.

Furthermore, in the present invention, since the oxygen concentration and the limiting current value are in a substantially proportional relationship, measurement is easy, and no reference gas is required as in the case of single-cell batteries.

Furthermore, the effects of using a box having diffusion holes (hereinafter referred to as a "perforated box") are as follows in comparison with the case where such a box is not used.

In other words, the present invention uses an effective box.

The electrode only needs to deliver the amount of oxygen that is available in mass quantities when a perforated box is not used. This means that the current and applied voltage required to obtain the limiting current characteristics can be lower than when no box is used. By selecting such a value, the current and applied voltage can be lowered.

Even if the gas to be measured has a relatively high oxygen concentration of 10° or more, the oxygen concentration can be measured with high accuracy over a long period of time without causing the oxygen ion transmitter to generate heat. In other words, if a perforated box is not used, the oxygen concentration in the gas to be measured is low, the current value required to obtain the limiting current characteristics becomes excessive, and it becomes necessary to apply a large voltage to the electrodes. However, when such a large current is passed through the device, the characteristics of the electrodes change significantly.

Oxygen gas may be forced through and damage the electrode.

In addition, the oxygen io-A transmitter generates self-heating due to the application of a large current and voltage, and this temperature change changes the current characteristics of the device, which adversely affects measurements. However, in the present invention, there is no such problem.

In addition, if a perforated box is not used, it is plated.

It is difficult to stably manufacture devices with the same performance because the limiting current characteristics differ depending on the method of installing the electrode on the oxygen ion permeable material, such as sputtering or vapor deposition, and the difference in electrode thickness (on the order of microns). 1. In the present invention, in order to utilize the rate-limiting diffusion of oxygen gas generated in the diffusion hole portion provided in the case, the method of forming the electrode is not influenced by the electrode conditions such as the thickness, and is almost the same. It is possible to stably manufacture high-performance devices.

Furthermore, if the perforated material itself is not used, the electrode itself has a limiting current characteristic corresponding to the oxygen concentration in the measured gas.
To take advantage of this, changes in electrode properties over time immediately affect the properties of the device. However, since the present invention utilizes the "diffusion rate-limiting rate of oxygen gas due to its own diffusion pores," the current flowing through the electrode is determined by the size of the diffusion pores, and the magnitude of the current is compared to the case where there is no oxygen gas. And quite small.

Therefore, even if the limit current characteristics of the electrode itself with respect to oxygen concentration change over time, the electrode retains the ability to sufficiently send out oxygen due to the diffusion rate control of the diffusion holes.

Therefore, in the device of the present invention, aging of the electrodes has little effect on the critical flow characteristics of the device with respect to oxygen concentration. Therefore, the device according to the present invention has excellent durability. To explain the above point using Figure 9, as shown in Figure 8, where the horizontal axis shows the oxygen concentration (%) and the vertical axis shows the ocular current value (mA, ), the initial characteristics of the device that does not use the is as shown by straight line C, but as the electrode changes over time, its characteristics deteriorate as shown by direct MC''.In contrast, in the device of the present invention.

Even if the electrode itself changes over time in the same way as above, the ocular current value depends on the diffusion of the diffusion hole and is quite low. It has a great influence on the characteristics of

In the present invention, the size of the diffusion holes provided in the box is such that a smaller amount of oxygen can be sent into the space inside the box by diffusion than the oxygen delivery capacity of the electrode. Therefore, there are no restrictions on the number or shape of the diffusion holes, and the box itself, excluding the oxygen ion permeable portion, may be made porous. However, in practice, the length of the diffusion hole is at most 2ONLH, depending on the thickness of the sensor, and if platinum, palladium, or silver, which is usually used as an electrode, is used, the length of the diffusion hole is It is desirable that the ratio of the area (8) of the opening of the diffusion hole to the surface area (A) of the facing portion of the cathode is 0.05 or less. In addition, the lower limit of the pore diameter is 005 mm, and below this the amount of oxygen gas passing through becomes too small.
There are 2 things that make the responsiveness worse. In addition, when the porous body itself is used as described above, it is sufficient that the total of the voids becomes the equivalent pore diameter of the above-mentioned diffusion hole openings. In other words,
The total area of the voids on the surface corresponding to the cathode is 0.5 or less of the surface of the cathode1.The material itself may cover the cathode; Due to the need to configure it, its own fabrication.

A practical method is to form a cathode and an anode on both sides of the oxygen ion permeable material as shown in the example, and then cover the oxygen ion permeable material on the cathode forming surface with a lid having a U-shaped cross section and adhere it. be. In terms of responsiveness, it is better for the space chamber formed inside the box to be as small as possible. Therefore, when the cathode itself is made of a porous material as described above, the porous material may be coated on the surface of the cathode. As for the material of the material other than the oxygen ion permeable material, airtight ceramics such as alumina, luconia, and magnesia are preferable from the viewpoint of heat resistance. Further, it is preferable that the thermal expansion coefficients of the oxygen ion permeable body and other parts thereof are similar to each other. 2. The material of the box is entirely the same as that of the oxygen ion permeable body, and a portion thereof can be provided with negative and positive poles.

The oxygen ion permeable body is a dense sintered body made by dissolving oxides of calcium, magnesium, or rare earths such as yttrium, ytterbium, and gadolinium in oxides of zirconium, hafnium, cerium, and thorium. There are kumquats. Further, as the electrode, a heat-resistant material having sufficient tetraelectricity at the operating temperature of the sensor is used.

These include platinum, palladium, and silver.

Therefore, the formation of an electrode on an oxygen ion permeable body.

This is accomplished by applying powder of these electrode materials in the form of a paste onto the oxygen ion permeable body and baking it, or by attaching these materials by sputtering, vacuum evaporation, chemical plating, or the like.

9 The temperature of the device according to the present invention is 600 to 1000°C.
It operates at such high temperatures that it is used to measure the oxygen concentration in the exhaust gas of internal combustion engines and the oxygen concentration in combustion gas. Also.

The gas to be measured at a low temperature is preheated to 60 to 1000'C and then supplied to a part of the sensor of this apparatus for measurement.

Embodiments Next, nine embodiments according to the present invention will be explained with reference to FIGS. 1 to 5.

The oxygen gas analyzer according to this example has a cylindrical sensor B as shown in Fig. 2 connected to a power supply circuit as shown in Fig. 1. Measurement cell 10 that can be heated and kept warm as shown in Figure 3
Attach it inside.

As shown in FIGS. 1 and 2, the sensor B has a disk-shaped cathode 2 formed on the upper surface of a disk-shaped oxygen ion permeable body 1 by sputtering, and the cathode 2 is formed on the lower surface of the disk-shaped cathode 2. Similarly, an anode 3 is formed on a portion facing the oxygen ion permeable body 1 on the side where the cathode 2 is provided.

A cylindrical lid 4 having an inverted U-shaped cross section and having a diffusion hole 5 for oxygen gas diffusion in its upper part is fixed so as to cover the cathode 2, thereby constituting itself 40. Thus, the space chamber 6 of the box 40 is formed by the inner wall of the lid 4, the oxygen ion permeable body 1, and the cathode 2. Further, the cathode 2 is connected to the cathode of a power source 7 through a lead wire 8, and the anode 6 is connected to a power source 7 through a lead wire 8.
An ammeter 9 and a voltmeter 10 for measuring the limiting current flowing between the electrodes are connected to the anodes of the power source 7, respectively, and the two electrodes are connected to the anode of the power source 7, respectively.

In the above, the oxygen ion permeable body 1 contains yttrium oxide dissolved in zirconium oxide as a solid electrolyte.
oy+), platinum was used for both the negative and negative electrodes 2 and 3, and a platinum wire was used for the lead wire 8°8'. A zirconia ceramic material was used as the lid 4, and the lid 4 and the oxygen ion permeable body 1 were bonded together with glass at 1000''C.

In addition, the oxygen ion permeable body 1 has a thickness of 0.5 mm and a diameter of 2
Both the 0o+ and 'vt poles 2 and 6 have a thickness of 1/7 and a diameter of 1 mm, and the lid body 4 has an outer diameter of 20 mm and a length of 2.1 am.
, wall thickness 4 mm, diffusion hole 5 diameter 0.5 mm, length 1
．． It was 7 mm.

Here, the area of the upper surface of the cathode 2 is 0.785 crA, and the opening area of the diffusion hole 5 is 0196 mm. Therefore, the ratio of the area (S) of the diffusion hole to the area (A) of the cathode is 8/
A is 1/400"?'

As shown in FIG. 3, the measurement cell 11 includes a cylindrical box 11 having an inlet nozzle 14 and an outlet nozzle 15 for the gas to be measured at both ends in the axial direction, and an outer surface of the box 11 in the circumferential direction. It consists of a heater 16 for heating and keeping warm, and has a fixing frame 13 and a buffer plate 12 for mounting the sensor B therein. The sensor B is fixed to the fixing frame 16 so that its diffusion hole 5 is positioned in the direction of the gas-filled cylinder/l/14. The fixed frame 13 is provided with an opening 161 for easily causing the gas to be measured to flow out in the direction of the gas outlet nozzle /l/15. Similarly, the buffer plate 12
has an opening 121 in a portion other than the portion facing the diffusion hole 5 of the sensor B to facilitate the flow of the temporary measurement gas 1L in the same way as described above.

Further, the lead wire 8.8' from the sensor B is connected to the terminal ear provided in the measurement cell/L/10.

The terminal 71/17'f: is connected to the terminal 7 through the terminal 71/17'f. A thermocouple 18 is installed in the measurement cell 10 to measure the internal temperature, and a temperature control device @ (not shown) and a heater 16 control the sensor B and the gas to be measured to an appropriate measurement temperature. Heat to.

Make sure to keep warm. Note that 161 is a lead wire of the heater 16.

Next, the results of measuring gases to be measured having various oxygen concentrations using the above device will be shown. For this measurement, a temporary measuring gaff was introduced from the Hegasian Ronoz)v14 while maintaining the temperature of the measuring cell/L/circle at approximately 700'C. A gas consisting of oxygen and nitrogen adjusted to two different oxygen concentrations was used as the gas to be measured. The injected gas is sent to the buffer plate 1
The gas is discharged from the outlet gas/shield 15 through the first part 121 of No. 2 and the opening 161 of the fixed frame 13 . At this time, in sensor B, oxygen gas flows into the space chamber 6 of sensor B from the diffusion hole 5 due to the diffusion of oxygen gas.

The oxygen gas that has flowed in this way is discharged to the outside of the sensor B by the electrodes 2 and 3 through the oxygen ion permeable body 1, and is discharged from the outlet nozzle 15 together with the gas to be measured. Therefore, the amount of oxygen flowing into the sensor through the hole 5 of sensor B is extremely small compared to the amount of oxygen in the gas to be measured that is introduced into the measurement cell/l/10. In this way, while supplying the gas to be measured, the voltage applied between the electrodes 2 and 3 was changed, and the current value at each voltage was measured. This measurement was performed for each gas to be measured having a different oxygen concentration. The results are shown in Figure 4, where the horizontal axis is the voltage (Vo
I t ) and current (mA) is plotted on the vertical axis.

Each oxygen concentration is shown as a curve. In FIG. 4, the values indicated by the measurement lines substantially parallel to the horizontal axis are the limiting current values at each oxygen concentration. FIG. 5 shows the relationship between the oxygen concentration (%) and the limiting current value (mA) obtained by the above measurements. This figure 5.

This serves as a calibration curve for the oxygen analyzer shown in this example. Therefore, when measuring the oxygen concentration in an unknown gas to be measured, the limiting current value for the gas is determined using the above device, and the oxygen concentration of the gas is determined from FIG.

Note that the above-mentioned apparatus was used for various measurements.

Despite long-term use, the values of the calibration curve (Figure 5) hardly curved, and even when measuring relatively high oxygen concentrations for a long period of time, it showed excellent measurement performance and stability.

Example The diameter and length of the diffusion holes in the box were varied.

Changes in limiting current values were measured.

That is, in the oxygen gas concentration analyzer similar to the one shown in the above example, various apparatuses were fabricated that differed only in the diameter and length of the diffusion holes 5 of the device 40, and an oxygen-nitrogen mixture with an oxygen concentration of 1% was prepared. About gas.

The limiting current value was measured at 825"C. The results are shown in Figure 6, with the horizontal axis representing the diameter of the diffusion hole and the vertical axis representing the limiting current value (mA). 9 curves 1..1. and l in the figure.

show the case of hole lengths of 2.5.5 and 10 mm, respectively. The horizontal axis of the figure also shows the ratio (S/A) of the area (S) of the opening of the diffusion hole to the area (A) of the cathode.

As can be seen from FIG. 6, the limiting current value decreases as the pore diameter becomes smaller, and when the pore diameter becomes less than a certain value, the limiting current value begins to drop rapidly.

Therefore, the region in which the rate of change in limiting current value with respect to change in hole diameter is large varies depending on the length of the hole. In areas where this rate of change is large, the limiting current value is.

This shows that it depends on the amount of oxygen reaching the electrode by diffusion from the diffusion holes, that is, it is in a state where the rate of diffusion is limited only by the diffusion holes as defined in the present invention.

For example, when the length of the diffusion hole is 2.5 wings (4I), this indicates that the pore diameter of 2 wings or less becomes diffusion rate-limiting. At the same time, when the length of the diffusion hole is 5 mm (Cl2) and 10 mm (ls), the hole diameter is approximately 4 ym or less than 7 mm, respectively. Although not shown in the figure, when the hole diameter is sufficiently large (for example, 11 mm or more), the limiting current value is approximately 60 mm.
It shows a constant value of 1IIA. In other words, a state where such a constant value is exhibited indicates that the rate-limiting state due to the diffusion holes no longer exists, and a high current will flow through the electrode, causing the problems described above. Also. In the same figure, in the region where the pore diameter is larger than the pore diameter that shows C1 diffusion rate limiting (for example, when the diffusion pore length is 2.5 mm, the pore diameter is 2 mm or more), the rate of increase in the limiting current value with respect to the increase in the pore diameter is almost constant and low. It seems that in this region, there is a mixture of the diffusion-limiting influence due to the diffusion pores and the influence of the oxygen delivery ability of the electrode. In other words, it shows a transitional state from a state where only diffusion is controlled to a state where there is no diffusion limited at all.

In summary, the present invention has an oxygen ion permeable body made of a solid electrolyte as its side wall.

In the oxygen ion permeable body, a cathode formed inside the box and an anode formed outside the box, a power source for applying a voltage between these two electrodes, and a current for measuring the limiting current flowing between the two electrodes. an oxygen gas concentration analyzer, characterized in that the box is provided with a diffusion hole that sends a smaller amount of oxygen than the oxygen delivery capacity of the electrode to the space chamber inside the box by diffusion. According to the present invention, compared to the device using the AFZ battery, it is easier.

Oxygen gas concentration can be measured with high accuracy.

Furthermore, according to the present invention, the amount of oxygen delivered by the electrode is controlled by diffusion by the diffusion holes, and the applied voltage and current required to obtain the limiting current characteristics can be lowered.
Compared to devices that do not use a perforated box, -C can also measure oxygen concentrations with high accuracy over a long period of time when measuring relatively high oxygen concentrations of 10'-3 or more. In addition, since the diffusion rate is controlled by diffusion holes, it can be used even if the limiting current characteristics change due to the manufacturing conditions of the electrode itself or changes over time.

It is possible to provide a durable oxygen gas concentration analyzer without affecting the limiting current characteristics of the device.

[Brief explanation of the drawing]

1 to 5 show nine embodiments of the present invention. Figure 1 is an explanatory diagram of the oxygen gas concentration analyzer, showing a cross-sectional view of the sensor and a circuit diagram of the device, Figure 2 is a partially cutaway perspective view of the sensor, and Figure 3 is a measurement cell in which the sensor is installed. Figure 4 is a diagram showing the relationship between voltage and current, which shows the limiting current value, Figure 5 is a diagram showing the relationship between oxygen concentration and limiting current value, and Figure 6 shows the pore diameter of the diffusion hole in the experimental example. A diagram showing the relationship between the limiting current value, FIG. 7 is a diagram showing the relationship between applied voltage and current for detailed explanation of the present invention, and FIG. In the device. This shows the difference in performance based on the aging of the electrode. FIG. 3 is a diagram showing the relationship between oxygen concentration and limiting current value. DESCRIPTION OF SYMBOLS 1... Oxygen ion permeable body, 2... Cathode, 6... Anode, 40... Box, 5... Diffusion hole, 10... Measurement cell) v, 12. Fist/a punch Plate, 16... Heater, 18
...Thermocouple 0, OH... Before and after the change over time of one electrode in a device that does not use a perforated box, D, IJ'・
...Before and after the electrode changes over time in the device of the present invention. Patent Applicant Toyota Central Research Institute Representative Director Noboru Komatsu Noboru Komatsu Noboru Noboru Taka Man Yasushi t%ノ

Claims (1)

[Claims] 1) A box in which at least a part of the side wall constituting a closed space is formed of an oxygen ion permeable body made of a solid electrolyte, a cathode provided on the inner wall surface of the oxygen ion permeable body, and a cathode provided on the outer wall surface of the box. It consists of an electrode consisting of an anode placed opposite to the electrode, a power source configured to apply a voltage between these two electrodes, and a "flow meter configured to measure the current flowing between the two electrodes," and the above-mentioned The box is provided with a diffusion hole that sends a small amount of oxygen into the internal space of the box by diffusion compared to the oxygen delivery capacity of the electrode, and the ratio of the area of the opening of the diffusion hole to the surface area of the cathode is provided. is 05
An oxygen gas concentration analyzer characterized in that the pore diameter is 0.05 mynφ or more and the pore length is 20 zm or less.