JPH11132995A - Nitrogen oxide detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the concns. of NO and NO2 in a measuring atmosphere by measuring the potential difference based on the concn. of nitrogen oxide of mixed NOx gas of NO and NO2 gases in atmospheric gas by a pair of electrodes and measuring the potential difference based on the concn. of nitrogen oxide converted to single gas such as NO or NO2 gas by a pair of other electrodes. SOLUTION: A detection electrode 1 having activity to nitrogen oxide and oxygen and a reference electrode 3 are formed on one surface of a solid electrolyte substrate 13 having oxygen ion conductivity and a detection electrode 2 not having activity to nitrogen oxide and having activity to oxygen and a reference electrode 4 are formed on the other surface thereof. Then, the potential difference E1 based on the concn. of nitrogen oxide consisting of NO and NO2 gases is measured by a pair of the electrodes 1, 2 and the potential difference E2 based on the concn. of nitrogen oxide converted to NO or NO2 , is measured by a pair of the other electrodes 3, 4. By performing operation by using these potential differences E1 , E2 , the individual concns. of NO and NO2 in a measuring atmosphere can be detected at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen oxide device for detecting a nitrogen oxide concentration.

[0002]

2. Description of the Related Art NOx emitted from combustion equipment such as automobiles and industrial furnaces is regarded as one of polluting gases that destroy the global environment, and it is desired to reduce it. Therefore, the necessity of detecting the NOx concentration for each generation source, and further controlling the combustion based on the NOx concentration is increasing. NOx concentration in the exhaust gas of an automobile and gas engines, NO, since the sum of the concentration of nitrogen oxides consisting of NO ₂ or the like, the presence ratio and the total concentration of the NO and NO ₂ varies by the combustion state. For the total NOx concentration, while being defined by the exhaust gas emission regulations, with respect to the composition of NOx, which may perform a more sophisticated combustion control by knowing the concentration of NO and NO ₂ to the individual.

Conventionally, several proposals have been made regarding the detection method of an all-solid-state NOx sensor. For example, JP-A-8
In the NOx sensor disclosed in JP-A-271476, NO is contained in a first can chamber provided in a zirconia solid electrolyte substrate.
introducing x test gas, of the NO and NO ₂ in NOx, only NO ₂ NO
NO introduced into the second canister communicating with the first canister
Is electrochemically electrolyzed and the oxygen ion current generated there is detected as a total NOx concentration.

In Japanese Patent Application Laid-Open No. Hei 9-113484, after the gas is converted into NO gas in the same manner as described above, it is
NO is decomposed into oxygen and nitrogen using a catalyst, and the density electromotive force according to the Nernst equation is measured based on the partial pressure of oxygen generated at that time, and the total
A method of detecting NOx concentration has been proposed. These are NOx sensors that are high-temperature operated sensors using an oxygen ion conductive zirconia solid electrolyte substrate and a noble metal electrode, and can be directly inserted into exhaust gas. However, the measurable NOx gas is the total NOx concentration,
And the abundance ratio of NO ₂ cannot be measured in principle. That is, NO, N in the exhaust gas NOx due to fluctuations in the combustion state, etc.
Changes in the individual concentrations of O ₂ cannot be detected.

On the other hand, the present inventor has also proposed a mixed potential type electromotive force NOx sensor obtained in the simultaneous presence of oxygen and NOx. In Japanese Patent Application No. 8-85419,
It is a method to measure the total NOx concentration of NO test NOx gas as mixed potential electromotive force of NO ₂ turned into NO ₂ gas. On the contrary, in Japanese Patent Application No. 8-165105, NO ₂
Is converted to NO and the total NOx concentration is measured as a mixed potential electromotive force of NO gas. Neither of these methods can simultaneously detect the individual concentrations of NO and NO ₂ in the test NOx gas.

[0006]

As described above, in the all solid-state sensor proposed so far, the total NO in the test gas is
It was difficult to simultaneously detect the x concentration and the abundance ratio of NO / NO ₂ or the individual concentrations of NO and NO ₂ . In the present invention,
It is an object to provide an all-solid-type NOx sensor the individual concentrations of NO and NO ₂ in the measurement atmosphere can be measured total NOx concentration at the same time can be detected.

[0007]

Means for Solving the Problems In view of the above problems, as a result of intensive research, the present invention solves the problems by providing the following means.
That is, the principles of the present invention, oxygen is fixed to the ion-conducting solid electrolyte substrate having a first detector for detecting the NOx and NO and NO ₂ are mixed, NO and NO ₂ and one of either one It consists of a second detection unit that converts the gas into gas and detects NOx, and the output of the first detection unit and the output of the second detection unit,
Calculated by the external calculation means, NO in the NOx gas to be detected
And there is provided a nitrogen oxide sensing apparatus characterized by simultaneously measuring the individual gas concentration of NO _2. The specific problem solving means in the present invention will be described below.

In the nitrogen oxide sensor of the present invention, a solid oxide substrate having oxygen ion conductivity is provided with at least a nitrogen oxide detection electrode having activity for nitrogen oxide and oxygen and a reference electrode having activity only for oxygen. A sensor structure in which two or more pairs are formed.
NO ₂ and measuring the potential difference based on the concentration of the nitrogen oxides consisting of a mixture NOx gas in the gas, the other pair of electrodes, and measuring the potential difference based on the concentration of a single gas converted nitrogen oxides to NO or NO ₂ gas, Total NO in atmospheric gas due to potential difference before and after conversion
It is characterized by detecting the x concentration and detecting the abundance ratios of NO and NO ₂ or their respective concentrations. In this case, there may be three or more pairs of the detection unit including the detection electrode and the reference electrode. This is because, for example, when simultaneously detecting the third detection target gas in the test gas, three or more pairs of plural detection units are required.

A more specific configuration of the sensor, that is, a configuration of the nitrogen oxide detector is provided as follows. That is, a first active substance for NOx and oxygen fixed to a solid electrolyte substrate having oxygen ion conductivity.
And the detection electrode (1), becomes from a first reference electrode in oxygen activity inert to NOx (3), a first sensing unit having an output characteristic in the reverse direction to and NO and NO _2, A second detection electrode (2) having the same output characteristics as the first detection unit;
A second detection unit including a reference electrode (4), and a means for calculating an electromotive force of the first detection unit and the second detection unit, wherein a detection target NOx mainly composed of NO and NO ₂ The electromotive force value obtained by measuring the gas with the first detection unit without changing the gas composition and the detection target NOx gas
Alternatively, by using an electromotive force value obtained by converting the gas into one of NO ₂ and being measured by the second detection unit, the individual NO and NO ₂ in the NOx gas to be detected by the external arithmetic means. The present invention provides a nitrogen oxide detection device characterized by simultaneously measuring the gas concentrations of nitrogen oxides.

Further, from the viewpoint of downsizing of the sensor, the response time of gas detection, and the accuracy of detection, it is preferable that the first detection unit and the second detection unit are closely integrated with each other. That is, the first detector and the second detector having the same output characteristics as the first detector are electrically connected to the same solid electrolyte substrate or a solid electrolyte using oxygen ions as a common conductor. It is provided with the above-mentioned nitrogen oxide detecting device formed on a substrate.

Further, as a more preferable specific sensor configuration, the detection electrode (1) of the first detection portion, or the detection electrode (1) and the reference electrode (3) are directly exposed to the gas atmosphere to be detected. At the same time, a second detection electrode (2) and a second reference electrode (4) provided in the internal space (12) of the solid electrolyte substrate communicating with the detection target gas atmosphere via the gas diffusion resistor. two detecting portions of the detection target NOx gas internal space (12) of the solid electrolyte internal space and at the same time a single gas into NO or NO ₂ by the substrate to form a gas conversion pumping electrode (5,6) (12) 3. The nitrogen oxide detecting apparatus according to claim 2, wherein oxygen is measured at a predetermined partial pressure. Note that the reference electrode 3 of the first detection section does not need to be directly exposed to the test gas atmosphere, but it is preferable to form an exhaust gas shielding layer from the viewpoint of electrode temperature stability. In addition, the diffusion resistor described above only needs to have a resistance enough to convert NOx gas sufficiently in the internal space 12, and it is not necessary to control the diffusion. It can be a body.

Further, in order for the first detection unit to perform stable measurement without being subjected to temperature fluctuation of the measurement atmosphere or temperature fluctuation due to gas flow, the following sensor configuration is more preferable. That is,
A first internal space (11) communicating with a gas atmosphere to be detected through a gas diffusion resistor is provided in the solid electrolyte substrate, and the detection electrode (1) is formed in the first internal space (11). And a second internal space (12) provided in the solid electrolyte substrate which is in direct communication with the gas atmosphere to be detected via a gas diffusion resistor.
Forming the second detection portion in the second internal space (12).
The NOx gas to be detected introduced into the second space (12)
That of the solid electrolyte at the same time the second internal space when a single gas into NO or NO ₂ by the substrate to form gas conversion pumping electrode (5,6) of oxygen (12) measured by controlling the predetermined partial pressure It is a nitrogen oxide detection device characterized by the following.

Further, in order to suppress the output fluctuation due to the oxygen concentration fluctuation in the measurement atmosphere, the following sensor configuration is more preferable. That is, the detection unit (1) is provided in the first internal space (11) in the solid electrolyte substrate communicating with the detection target gas atmosphere via the gas diffusion resistor, and the solid in the first internal space (11) is provided. An oxygen pump electrode (7, 8) having no NOx conversion capability for controlling the oxygen partial pressure formed on the electrolyte substrate, and further comprising the gas communicating with the gas atmosphere to be detected via a gas diffusion resistor. The NOx gas to be detected by the second detector provided in the second internal space (12) of the electrolyte substrate is supplied to a gas conversion pump electrode (5, 6) formed on the solid electrolyte substrate of the second internal space (12). ) To convert it to NO or NO ₂ as a single gas and at the same time to the second internal space (1
2) A nitrogen oxide detection device characterized in that oxygen is controlled at a predetermined partial pressure and measured. Here, the internal space 11
The pump electrodes 7 and 8 need to have a function of simply performing oxygen pumping, and it is necessary to suppress the NOx conversion catalytic ability as much as possible. Therefore, a material in which Au is added to Au or Pt is usually used. The gas pumping resistance of the pump electrode is set so that the oxygen concentration in the internal space can be sufficiently controlled.

[0014] Further, in order to perform more accurate and stable measurement, it is more desirable to keep the oxygen concentration in the detecting section constant. That is, the inner space 11 in which the first detection unit is formed
And the oxygen concentration of the internal space 12 in which the second detection section is formed is controlled to a constant value within a range of 0.1 to 30%. is there.

An example of a specific detection calculation method in the nitrogen oxide sensor of the present invention will be described below. The present invention is not limited to the calculation methods exemplified below from the concept of the present invention, and its improvement methods and the like are also included in the present invention. For example, the output potential based on the mixed potential type electromotive force is E _NO and E _NO2 respectively with respect to NO and NO ₂ concentrations before gas conversion, and exists before conversion.
When the concentrations of NO and NO ₂ are X _NO and X _NO2 , respectively, E _NO and
E _NO2 , X _NO , and X _NO2 are represented by a relational expression using the following logarithm. If a and b are positive constants, NO for mixed potential type
NO ₂ has an output in the opposite direction in principle.
In the formula, a minus sign is added. E _NO = -aln (X _NO ) ………………………………………………… (1) E _NO2 = bln (X _NO2 ) …………………………… (2) NO before gas conversion And the electromotive force generated based on the concentration of NO ₂ is E ₁
Then, the potential E _{1 of} the first detection unit based on the concentrations of NO and NO ₂
Becomes _{E 1 = E NO2 + E NO} = bln (X NO2) -aln (X NO) ............ (3). On the other hand, to convert the NO gas in the atmosphere to NO ₂ gas by the gas conversion pump, if only a single gas NO ₂ touches the sense electrode 2, when the electromotive force of the converted and E ₂ E ₂ = b {1n (X _NO2 + X _NO )｝ …………… (4) Electromotive force after the electromotive force E ₁ and gas conversion before gas conversion
Taking the difference between _{E 2 E 2 -E 1 = b} {1n (X NO2 + X NO)} - {b1n (X NO2) - a1n (X NO)} = b1n {(X NO2 + X NO) / _{X NO2} + a1n (X NO} ) ...... (5) = become b1n _{[1+ X NO / exp {E 1} + a1n (X NO)} ] _{+ a1n (X NO) ... (} 6).

[0016] Thus, nitrogen oxide sensor of the present invention can be obtained NO concentration X _NO in the atmosphere gas by measuring the electromotive force E ₂ after the electromotive force E ₁ and gas conversion before gas conversion. Further, X _NO2 is obtained by substituting X _NO into the equation (4), and the respective concentrations of NO and NO ₂ in the atmospheric gas can be calculated. Further, in the nitrogen oxide sensor of the present invention, even if the gas conversion pumps 5 and 6 do not convert 100% from NO to NO ₂ , if the gas conversion rate (η) is known, N
The individual concentrations of O and NO ₂ can be determined from the following formula. _{E 2 - E 1 = η <} b1n _{[1+ X NO / exp {E 1} + a1n (X NO)} ] _{+ a1n (X NO)> ..........................................} (7)

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the nitrogen oxide sensor according to the present invention will be described below with reference to the drawings. FIG. 1 shows the basic configuration of the nitrogen oxide sensor of the present invention. In the nitrogen oxide sensor of the present invention, a first detection electrode 1 and a second detection electrode 2 having activity on nitrogen oxide and oxygen are formed on one surface of a solid electrolyte substrate 13 having oxygen ion conductivity. A first reference electrode 3 and a second reference electrode 4 on the other surface which are inactive against nitrogen oxides and active on oxygen.
Is further formed of solid electrolyte substrates 13 and 14 having oxygen ion conductivity and communicating with the gas atmosphere to be detected by two gas diffusion resistors (diffusion resistors 9 and 10). Oxygen gas is pumped into both sides of the substrate 14 and formed in the internal cavities 11 and 12,
Gas conversion pump electrodes 5 and 6 for converting to NO ₂ gas are formed in the second internal space 12. When converting NO ₂ to NO, the pump electrode is driven in the reverse direction. In order to expose the first reference electrode 3 and the second reference electrode 4 to the atmosphere, a spacer sheet 15 and an upper holding sheet 16 made of ceramic are formed. It is desirable that the sensor has a structure in which NO and NO ₂ flowing from the gas diffusion resistor 9 touch the gas conversion pump electrodes 5 and 6 before touching the second detection electrode 2. This is because such a structure improves the efficiency of converting NO gas in the atmosphere into NO ₂ gas.

The reference electrodes 3, 4 and the gas conversion pump electrodes 5, 6 are formed of an electrode material such as a noble metal active on oxygen, such as Pt, Rh, Ir, or Pd, an alloy thereof, or a cermet of a noble metal and a metal oxide. Is done. As the electrode material, it is more preferable to use Pt, Rh, or a cermet of these with a zirconia solid electrolyte substrate from the viewpoint of thermal stability and chemical stability. When a pump electrode is installed to control the oxygen concentration in the first internal space 11, an electrode material that does not cause NOx conversion is selected. Usually, Au or a Pt-Au alloy is used.

[0019] Gas conversion pumping electrodes 5 and 6, NO introduced through the diffusion resistor 9, the nitrogen oxides consisting of NO ₂ is, NO ₂
It is necessary to have sufficient oxygen pumping ability to be converted to a single gas of 0.1%, and the sum of oxygen gas flowing in through the diffusion resistor 10 and oxygen gas pumped by pumping is 0.1 to 30%. Needs to have sufficient oxygen pumping ability to be controlled so as to be constant within the range.

The sensing electrodes 1 and 2 are formed of oxygen and a noble metal or a noble metal alloy such as Pt, Rh, Ir, or Pd active for NO and NO ₂ , a noble metal-oxide cermet, and an oxide of a transition metal. Is done.

The solid electrolyte substrates 13 and 14 are oxygen ion conductors, and may be a solid electrolyte substrate obtained by adding a stabilizer to an oxide such as zirconium oxide, hafnium oxide, thorium oxide, or cerium oxide, or bismuth oxide. . From the viewpoint of thermal stability and chemical stability, it is preferable to use stabilized zirconia using a stabilizer such as yttrium oxide, magnesium oxide, or calcium oxide.

The gas diffusion resistor 9 is provided in the detection atmosphere gas.
Nitrogen oxide composed of NO and NO ₂ is set to a size sufficient to flow into the first internal space 11. First internal space 1
The NOx gas introduced into 1 further diffuses and flows into the second internal space 12. Gas diffusion resistor 10 must NO flowing, NO ₂ is set to a size for being converted to a single gas NO ₂ gas conversion pump. Here, the diffusion hole may be formed with one fine hole or a porous body including a plurality of holes.

The atmosphere gas to be detected flows into the first internal space 11 through the diffusion resistor 9, and the nitrogen oxides composed of NO and NO ₂ flowing into the first internal space 11 are removed by the first detecting section. In N
A detection output in which O and NO ₂ interfere with each other is obtained. Further, the gas flows from the gas diffusion resistor 8 and is converted into NO ₂ gas by the gas conversion pump electrodes 5 and 6. The converted NO ₂ gas is
Touch the detection electrode 2 and use the second detection unit to detect N corresponding to the total NOx concentration.
A potential change based on the O ₂ concentration occurs. In the nitrogen oxide sensor of the present invention, the detection electrode 2 and the gas conversion pump electrodes 5 and 6 are formed in the same chamber, but the additional diffusion resistor 1 is used.
2, that is, even if the gas conversion pump electrodes 5 and 6 are independently disposed in separate chambers, there is no problem in the configuration of the present invention.

Since the nitrogen oxide sensor of the present invention uses a solid electrolyte substrate exhibiting oxygen ion conductivity at a high temperature, it is necessary to heat the sensor to a predetermined temperature. As a heating means, a self-heating device may be added for heating to a predetermined temperature, or heating may be performed in high-temperature exhaust gas.

[Embodiment 1] An embodiment of the nitrogen oxide sensor of the present invention will be described below. Yttria-stabilized zirconia green sheets (thickness: 400 μm, P sheets 13, 14, 16 and alumina green sheets (thickness: 200 μm, P sheets 15, 18) cut by a doctor blade method to a width of 12 mm and a length of 60 mm ( At the time of cutting, a diffusion resistor 9 having a width of 0.8 mm and a length of 5 mm was provided on the alumina green sheet 18. A Pt / Rh electrode (detection electrode) was formed on one surface of the zirconia sheet 13 by a screen printing method. Pt electrodes (reference electrodes 3 and 4) were formed on the other side by screen printing, and then on both sides of the zirconia sheet 14 by screen printing.
Pt electrodes (gas conversion pump electrodes 5, 6) were formed. After attaching a Pt lead wire to each electrode, the green sheets were overlapped as shown in FIG. 1 and fired in the air at 1400 ° C. to produce the nitrogen oxide sensor shown in FIG. From the test gas inlet, the prepared sample was added with 20 to 400 ppm of NO.
21% O ₂ and NO ₂ are set in a tubular furnace so that a test gas of ₂₀ to 400 ppm + 21% O ₂ is introduced, and the atmosphere is introduced from an atmosphere introduction port, heated to 600 ° C., and a nitrogen oxide electrode 1
And the electromotive force generated between the electrodes 3 was measured. At this time,
No voltage was applied between the gas conversion pump electrodes 5 and 6. FIG. 3 shows the measurement results. Detection electrode 1 and reference electrode 3
The electromotive force generated during the period decreased as the NO concentration increased, and increased as the NO ₂ concentration increased. From the measurement results, the electromotive forces based on the NO and NO ₂ concentrations were approximated by the following equations, respectively. E _NO = -5.325 ln (X _NO ) E _NO2 = 18.452 ln (X _NO2 )

Next, a voltage of 1 V is applied to the gas conversion pump electrode, a mixed gas of _{20 to} 200 ppm of NO + _{20 to} 200 ppm of NO ₂ is introduced, and a gas is applied between the detection electrode 1 and the reference electrode 3 and between the detection electrode 2 and the reference electrode 4. The generated electromotive force was measured. Table 1 shows the results.

[0027]

[Table 1]

Next, E ₁ and E ₂ obtained from the measurement are represented by (6),
The NO and NO ₂ concentrations were calculated by substituting into equation (4). Table 2 shows the calculation results.

[0029]

[Table 2]

From the calculation results, the calculated NO and NO ₂ concentrations and the charged concentrations are substantially equivalent, and the electromotive force between the electrodes 1 and 3 (E ₁ ) and the electromotive force between the electrodes 2 and 4 (E ₂ ), It was confirmed that NO and NO ₂ concentrations could be detected simultaneously.

[0031]

According to the nitrogen oxide sensor of the present invention, the potential difference based on the concentration of nitrogen oxide composed of NO and NO ₂ gas is measured at one pair of electrodes, and converted to NO or NO ₂ at the other pair of electrodes. By measuring the potential difference based on the concentration of nitrogen oxides, the respective concentrations of NO and NO ₂ in the measurement atmosphere can be simultaneously detected. In addition, the fact that the total NOx concentration can be detected at the same time has a very large effect particularly in performing combustion control more precisely.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nitrogen oxide sensor according to the present invention.

FIG. 2 is a cross-sectional view of a nitrogen oxide sensor according to the present invention.

FIG. 3 is a diagram showing the NO and NO ₂ concentration dependence of the electromotive force of a nitrogen oxide detection electrode.

[Explanation of symbols]

 1, 2 Detection electrode 3, 4 Reference electrode 5, 6 Gas conversion pump electrode 7, 8 Oxygen pump electrode 9, 10, 17 Diffusion resistor 11, 12 Internal space 13, 14, Solid electrolyte substrate

Claims (7)

[Claims] 1. A immobilized on a solid electrolyte substrate having oxygen ion conductivity, converting a first detector for detecting the NOx and NO and NO ₂ are mixed, the NO and NO ₂ to the one of the gas And a second detection unit for detecting this, and using the electromotive force of the first detection unit and the electromotive force of the second detection unit, NO and NO ₂ in the NOx gas to be detected by external calculation means. A nitrogen oxide detection device characterized by simultaneously measuring individual gas concentrations. 2. A first sensing electrode (1) fixed to NOx and oxygen fixed to a solid electrolyte substrate having oxygen ion conductivity, and a first reference active to oxygen and inert to NOx. becomes because the electrode (3), and a first sensing unit having an output characteristic in the reverse direction to the NO and NO _2, the second detecting electrodes having the same output characteristics as the first detection section (2) the a second detecting portion consisting a second reference electrode (4), the first detecting unit and the second detecting unit a structure formed by using the means for calculating the electromotive force of the detection target mainly composed of NO and NO ₂ electromotive force values obtained by measurement in the first detection unit without the NOx gas changes its gas composition, the first by converting the detection target NOx gas on either a single gas nO or nO ₂ (2) Using the electromotive force value obtained by measurement by the detection unit, the detection target NOx Nitrogen oxide sensing apparatus characterized by simultaneously measuring the individual gas concentration of NO and NO ₂ in. 3. The method according to claim 1, wherein the first detection unit and the second detection unit are formed on the same solid electrolyte substrate or on an electrically connected solid electrolyte substrate using oxygen ions as a common conduction carrier. The nitrogen oxide detection device according to claim 1 or 2, wherein: 4. The detection electrode (1) of the first detection portion, or the detection electrode (1) and the reference electrode (3) are directly exposed to the gas atmosphere to be detected, and at the same time, are detected via the gas diffusion resistor. The NOx gas to be detected by the second detection section, which is composed of the second detection electrode (2) and the second reference electrode (4) provided in the internal space (12) of the solid electrolyte substrate communicating with the target gas atmosphere, oxygen measurement is controlled to a predetermined partial pressure of the cavity (12) of the solid electrolyte internal space and at the same time a single gas into NO or NO ₂ by the substrate to form gas conversion pumping electrode (5,6) (12) 3. The nitrogen oxide detecting device according to claim 2, wherein: 5. A first internal space (11) communicating with a gas atmosphere to be detected through a gas diffusion resistor in the solid electrolyte substrate, and the detection electrode (11) is provided in the first internal space (11). 1), and further into the second internal space (11) via the gas diffusion resistor or the second internal space (12) provided in the solid electrolyte substrate which directly communicates with the gas atmosphere to be detected. The second detection portion is formed, and the NOx gas to be detected introduced into the second internal space (12) is supplied to a gas conversion pump electrode (5, 5) formed on the solid electrolyte substrate in the second internal space (12). 3. The nitrogen oxide detector according to claim ₂ , wherein the gas in the second internal space (12) is controlled at a predetermined partial pressure and measured at the same time as the single gasification to NO or NO2 by (6). 6. A detection unit (1) in a first internal space (11) in the solid electrolyte substrate that communicates with a gas atmosphere to be detected via a gas diffusion resistor, and the first internal space (1).
The oxygen pump electrode (7, 2) having no NOx conversion capability for controlling the oxygen partial pressure formed on the solid electrolyte substrate of 1).
8), and the detection target NO of the second detection unit provided in the second internal space (12) of the solid electrolyte substrate that communicates with the detection target gas atmosphere via a gas diffusion resistor.
The x gas is supplied to the solid electrolyte substrate in the second internal space (12) through the gas conversion pump electrodes (5, 6) formed of NO or NO.
_3. The nitrogen oxide detecting device according to claim 2, wherein oxygen gas in the second internal space (12) is controlled at a predetermined partial pressure and measured at the same time as the single gasification to NO2. 7. The oxygen concentration in the first internal space (1) and the second internal space (2) is controlled to a constant value in a range of 0.1 to 30%. 7. The nitrogen oxide detector according to claim 4.