NOx and NH3 concentration synchronous measurement method and system

Abstract

The invention relates to a NOx and NH3 concentration synchronous measurement method and system. The method comprises the following steps: applying excitation voltage to a first oxygen pump of a NOx sensor; when the excitation voltage is applied, synchronously collecting an output signal of the NOx sensor; respectively performing Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal to obtain a frequency domain feature vector of the excitation voltage and a frequency domain feature vector of the output signal; and constructing an overdetermined equation set according to the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal obtained under the application of different excitation voltages, and solving to obtain the NOx concentration and the NH3 concentration. Compared with the prior art, the method has the advantages that the problem of cross sensitivity of NH3 to NOx measurement is solved, measured values of NOx and NH3 concentrations are synchronously provided, and the measurement precision of the NOx concentration and the NH3 concentration is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive exhaust aftertreatment technology, and in particular to a NO... x Method and system for simultaneous measurement of NH3 concentration. Background Technology

[0002] With increasingly stringent global emission regulations, Selective Catalytic Reduction (SCR) technology has become one of the core technologies in diesel vehicle exhaust aftertreatment systems. SCR systems reduce nitrogen oxides (NOx) in exhaust gases by injecting urea (which decomposes into ammonia (NH3)). x To achieve efficient closed-loop control of the SCR system, accurate measurement of NO downstream of the catalyst is required. x concentration.

[0003] Currently widely used NO x The sensor is a dual-chamber current-limiting amperometric sensor based on a zirconium oxide solid electrolyte. Its basic principle is as follows: the first chamber is pumped to a stable oxygen partial pressure by a first oxygen pump, while the Pt electrode catalyzes the oxidation of some easily oxidizable gases; the second chamber is then pumped by a second oxygen pump to remove NO diffused from the first chamber. x The NO is calculated by measuring the limiting current corresponding to the amount of oxygen produced during decomposition, which decomposes into N2 and O2. x concentration.

[0004] However, the existing NO x The sensor has a serious technical flaw: cross-sensitivity to NH3. When an NH3 leak occurs in the SCR system, unreacted NH3 will enter the NO₃⁻ layer. x Sensor. At the high-temperature Pt electrode in the first chamber, NH3 will be oxidized to NO or N2 (e.g., 4NH3 + 5O2 → 4NO + 6H2O). If oxidized to NO, it will cause the sensor reading to be falsely high, resulting in NO... x Incorrect concentration measurement can affect the closed-loop control accuracy of the SCR system, leading to increased NO concentration. x Excessive NH3 emissions or waste of urea. Existing solutions include: 1) In NO x 1) Connecting an NH3 sensor in series with the main sensor increases the cost and complexity of the system; 2) Software compensation is performed by establishing an NH3 leakage model based on engine operating conditions, but the model is complex and has limited accuracy; 3) Improving the sensor structure or materials results in high R&D costs.

[0005] Traditional NO x The sensor uses a constant voltage to drive the first oxygen pump, and inversely calculates the NO content by using the limiting current value. xConcentration. However, in practical applications, sensor output is easily affected by factors such as temperature fluctuations, airflow changes, NH3 cross-interference, and sensor aging, leading to measurement deviations. Furthermore, when NO is also present in the exhaust gas... x When NOx and NH3 react, their reactions at the sensor electrodes exhibit competition and coupling. A single steady-state response cannot distinguish the contributions of each, leading to an underdetermined problem and preventing synchronous measurement. For example, patent application CN109312655A discloses a method for detecting NH3 leakage using a NOx sensor. This method compares the NOx downstream of the SCR... x The deviation between the sensor's measured signal and the estimated value is set at a threshold under high or low temperature conditions. If the deviation value or NO... x If the average value of the measured signal consistently exceeds the threshold, an NH3 leak is detected and a flag is set. This method relies solely on NO. x The sensor's original defect (cross-sensitivity to NH3) indirectly determines NH3 leakage, neither eliminating NH3 cross-interference nor simultaneously obtaining NH3 concentration.

[0006] Therefore, there is an urgent need for a low-cost, high-precision, and high-response-speed method to eliminate existing NO. x The sensor is cross-sensitive to NH3 and can simultaneously acquire NH3 concentration information. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method and system for simultaneous measurement of NOx and NH3 concentrations.

[0008] The objective of this invention can be achieved through the following technical solutions: A NO x The method for simultaneous measurement of NH3 concentration includes the following steps: NO x The sensor's first oxygen pump applies an excitation voltage; While applying the excitation voltage, NO is simultaneously collected. x The sensor's output signal; Perform Fourier transforms on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal. Based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, an overdetermined system of equations is constructed and solved to obtain NO. x Concentration and NH3 concentration.

[0009] Furthermore, the NO xThe sensor is a dual-chamber current-limiting amperometric sensor based on zirconium oxide solid electrolyte, including a first chamber and a second chamber. A first oxygen pump is provided in the first chamber, and a second oxygen pump and a measuring pump are provided in the second chamber.

[0010] Furthermore, the excitation voltage changes dynamically over time, and is obtained by superimposing a periodic AC signal onto a DC bias voltage. The excitation voltage is: In the formula, For excitation voltage, For time, This is the DC bias voltage. It is a periodic alternating signal.

[0011] Furthermore, the frequency of the periodic AC signal is set at the NO. x The sensor's electrochemical system is able to respond normally and is within the range that causes changes in the oxidation rate of NH3 on the Pt electrode.

[0012] Furthermore, the NO x The sensor's output signal is the pump current of the measuring pump, and its calculation formula is as follows: In the formula, For output signal, NO x Sensor sensitivity, NO x concentration, The concentration of NH3. The conversion of NH3 to NO x Conversion rate The surface area of ​​the Pt electrode in the first chamber used for the NH3 oxidation reaction. It is a natural exponential function. When all active sites on the Pt electrode surface are completely covered by NH3, NH3→NO x The theoretical maximum rate that the reaction can achieve. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–O bonds on the Pt electrode surface. The gas constant is... Operating temperature Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. As a competitive adsorption term, Let be the adsorption equilibrium constant of O2 on the Pt electrode surface. This represents the partial pressure of oxygen within the first chamber. This represents the theoretical maximum rate that the NH3→N2 reaction can achieve when all active sites on the Pt electrode surface are completely covered by O2. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–N bonds on the Pt electrode surface. is the desorption rate constant.

[0013] Furthermore, the partial pressure of oxygen within the first chamber is: In the formula, This represents the partial pressure of oxygen within the first chamber. For reference oxygen partial pressure, It is a natural exponential function. It is Faraday's constant. The gas constant is... Operating temperature The excitation voltage; The competitive adsorption term is: In the formula, As a competitive adsorption term, Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. This refers to the concentration of NH3.

[0014] Furthermore, the frequency domain feature vector includes amplitude and phase information of the signal sequence at the fundamental frequency and harmonic frequencies.

[0015] Furthermore, the overdetermined system of equations is as follows: In the formula, To obtain the frequency domain eigenvector of the output signal under the first applied excitation voltage, For the model function of support vector machines, For the frequency domain eigenvector of the first excitation voltage, NO x concentration, The concentration of NH3. To obtain the frequency domain eigenvector of the output signal under the second excitation voltage, For the frequency domain eigenvector of the second excitation voltage, To obtain the frequency domain eigenvector of the output signal under the application of the Mth excitation voltage, Let be the frequency domain eigenvector of the Mth excitation voltage; The NO x The concentration estimates of NH3 and NH4+ were obtained by fitting the solution using the least squares method, where the objective function of the least squares method is: In the formula, Let the objective function be the least squares method. The number of different excitation voltages, In the first The frequency domain eigenvector of the output signal is obtained under the application of an excitation voltage. In the first The frequency domain eigenvector of the excitation voltage, It is the vector norm.

[0016] Furthermore, based on various known NO... x The combined concentration of NH3 and the frequency domain eigenvectors of the excitation voltage and output signal collected under different operating conditions, along with their corresponding NO concentrations. x The actual concentration of NH3 was used to train the support vector machine through offline calibration.

[0017] According to another aspect of the invention, a NO is provided. x The system for simultaneous measurement of NH3 concentration includes: Excitation voltage application module, used to apply excitation voltage to NO x The sensor's first oxygen pump applies an excitation voltage; The output signal acquisition module is used to simultaneously acquire NO while the excitation voltage is applied. x The sensor's output signal; The frequency domain feature vector acquisition module is used to perform Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal. The synchronous measurement module is used to construct and solve an overdetermined system of equations based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, to obtain NO. x The concentrations of NH3 and NH4+.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention is based on existing commercially available NO. x The sensor hardware, through sending NO x The sensor's first oxygen pump applies an excitation voltage and simultaneously collects NO. x The sensor's output signal is obtained by solving for NO based on the frequency domain eigenvectors of the excitation voltage and the output signal under different excitation voltages. x Concentration and NH3 concentration, solving the problem of NH3's effect on NO x The measurement cross-sensitivity issue was addressed, and NO was provided simultaneously. xThe measured values ​​of NH3 concentration provide richer control inputs for the SCR system.

[0019] 2. This invention, based on frequency domain analysis and support vector machines, fully mines NO by using the frequency domain feature vectors of the excitation voltage and the output signal obtained under different excitation voltage applications. x By extracting deeper information from the sensor's dynamic response, a more accurate set of overdetermined equations for concentration calculation can be constructed, which can then be used to obtain the NO concentration. x Concentration and NH3 concentration increased NO x The accuracy of concentration and NH3 concentration measurement. Attached Figure Description

[0020] Figure 1 This invention proposes a NO x A schematic diagram of the method for simultaneous measurement of NH3 concentration; Figure 2 This is a schematic diagram showing the relationship between the excitation voltage signal and the output signal. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] The following English abbreviations are involved: Selective Catalytic Reduction (SCR) Support Vector Machine (SVM) Example 1 This embodiment provides a NO x Methods for simultaneous measurement with NH3 concentration, such as Figure 1 As shown, it includes the following steps: S1, To NO x The sensor’s first oxygen pump applies an excitation voltage.

[0023] NO x The sensor is a dual-chamber current-limiting amperometric sensor based on zirconium oxide solid electrolyte, including a first chamber and a second chamber. A first oxygen pump is installed in the first chamber, and a second oxygen pump and a measuring pump are installed in the second chamber.

[0024] The catalytic oxidation efficiency of the Pt electrode in the first chamber for NH3 is highly sensitive to the oxygen partial pressure within that chamber, which is influenced by the oxygen content in the NO3-carrying chamber. xThe sensor's first oxygen pump applies an excitation voltage to quantitatively set the oxygen partial pressure within the first chamber. The voltage of the second oxygen pump is adjusted based on the excitation voltage of the first oxygen pump to ensure complete pumping of oxygen. The excitation voltage dynamically changes over time and is obtained by superimposing a periodic AC signal onto a DC bias voltage. The excitation voltage is: In the formula, For excitation voltage, For time, This is the DC bias voltage. This is a periodic alternating current signal. A periodic alternating current signal can be a sine wave, square wave, or triangle wave, and its frequency is set at NO. x The sensor’s electrochemical system is able to respond normally and can cause changes in the oxidation rate of NH3 on the Pt electrode within a range, for example, from 1 Hz to 100 Hz.

[0025] S2. Simultaneously, NO is collected while applying the excitation voltage. x The sensor's output signal.

[0026] NO x The sensor's output signal is the actual NOx concentration in the exhaust gas. NH3 concentration and excitation voltage The result of combined action. Due to Periodic changes, It will also exhibit corresponding cyclical changes. NO x The sensor's output signal measures the pump current, and its calculation formula is as follows: In the formula, For output signal, NO x Sensor sensitivity, NO x concentration, The concentration of NH3. The conversion of NH3 to NO x conversion rate The diagram showing the relationship between the excitation voltage signal and the output signal is as follows: Figure 2 As shown, the excitation voltage signal and the output signal have the same frequency. The amplitude of the excitation voltage signal varies between 0.3 and 0.7, while the amplitude of the output signal varies between 0.5 and 1.1. The amplitude of the output signal is affected by the excitation voltage signal, and there is a phase delay between the excitation voltage signal and the output signal.

[0027] The oxygen pump in the first chamber is a solid electrolyte electrochemical cell. The relationship between its voltage and the partial pressure of oxygen in the chamber follows the Nernst equation. The partial pressure of oxygen in the first chamber is: In the formula, This represents the partial pressure of oxygen within the first chamber. For reference oxygen partial pressure, It is a natural exponential function. It is Faraday's constant. The gas constant is... Operating temperature The excitation voltage; At the Pt electrode, NH3 is partially oxidized ( ) and complete oxidation ( The two molecules are in a competitive relationship and are highly sensitive to oxygen partial pressure. Therefore, NH3 is converted to NO. x The conversion rate is a function of the oxygen partial pressure, specifically expressed as: In the formula, The conversion of NH3 to NO x Conversion rate The concentration of NH3. The surface area of ​​the Pt electrode in the first chamber used for the NH3 oxidation reaction. It is a natural exponential function. When all active sites on the Pt electrode surface are completely covered by NH3, NH3→NO x The theoretical maximum rate that the reaction can achieve. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–O bonds on the Pt electrode surface. The gas constant is... Operating temperature Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. As a competitive adsorption term, Let be the adsorption equilibrium constant of O2 on the Pt electrode surface. This represents the partial pressure of oxygen within the first chamber. This represents the theoretical maximum rate that the NH3→N2 reaction can achieve when all active sites on the Pt electrode surface are completely covered by O2. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–N bonds on the Pt electrode surface. is the desorption rate constant.

[0028] The competitive adsorption term is: In the formula, As a competitive adsorption term, Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. The concentration of NH3. Let be the adsorption equilibrium constant of O2 on the Pt electrode surface. This is the partial pressure of oxygen within the first chamber.

[0029] S3. Perform Fourier transform on the excitation voltage signal sequence and the output signal signal sequence respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal.

[0030] Within a fixed time window, the acquired excitation voltage signal sequence is analyzed. and output signal sequence Perform Fourier transforms on each to obtain their frequency domain eigenvectors: In the formula, Let be the frequency domain eigenvector of the excitation voltage. For Fourier transform, For excitation voltage, This is the frequency domain eigenvector of the output signal. This is the output signal.

[0031] Frequency domain feature vectors include the amplitude and phase information of the signal sequence at the fundamental and harmonic frequencies. The amplitude and phase information together reflect the sensor system's response to NO under specific frequency excitation. x The combined response characteristics of NH3. This step effectively overcomes the time-domain delay problem caused by gas diffusion and reaction.

[0032] S4. Based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, construct an overdetermined system of equations and solve it to obtain NO. x Concentration and NH3 concentration.

[0033] The overdetermined system of equations is as follows: In the formula, To obtain the frequency domain eigenvector of the output signal under the first applied excitation voltage, For the model function of support vector machines, For the frequency domain eigenvector of the first excitation voltage, NO x concentration, The concentration of NH3. To obtain the frequency domain eigenvector of the output signal under the second excitation voltage, For the frequency domain eigenvector of the second excitation voltage, To obtain the frequency domain eigenvector of the output signal under the application of the Mth excitation voltage, Let be the frequency domain eigenvector of the Mth excitation voltage; NO x The concentration estimates of NH3 and NH4+ were obtained by fitting the solution using the least squares method. The objective function of the least squares method is: In the formula, Let the objective function be the least squares method. The number of different excitation voltages, In the first The frequency domain eigenvector of the output signal is obtained under the application of an excitation voltage. In the first The frequency domain eigenvector of the excitation voltage, It is the vector norm.

[0034] During the training of SVM, based on various known NOs x The combined concentration of NH3 and the frequency domain eigenvectors of the excitation voltage and output signal collected under different operating conditions, along with their corresponding NO concentrations. x The actual concentration of NH3 was used to train the SVM through offline calibration.

[0035] Example 2 This embodiment follows the NO proposed in Embodiment 1. x Simultaneous measurement method with NH3 concentration, in the case of NO x When sensor response performance requirements are reduced, a quasi-static measurement method is adopted, including the following steps: At least two (preferably three or more) different, preset constant DC voltage combinations are sequentially applied to the first oxygen pump and the second oxygen pump. The voltage of the first oxygen pump is denoted as... , ,in The voltage of the second oxygen pump is adjusted based on the voltage of the first oxygen pump to ensure that oxygen is completely pumped out in the second oxygen pump. The voltage of the first oxygen pump... Sustained for a period of time enough to make NO x The time it takes for the sensor output to reach a steady state.

[0036] At each constant DC voltage Under the influence of this process, the corresponding stabilized NO was collected. x Sensor output value This results in a set containing multiple data pairs. Construct an overdetermined system of equations based on the set: In the formula, NO x Sensor output value, For the model function of support vector machines, NO x concentration, The concentration of NH3. This is the voltage of the first oxygen pump.

[0037] The overdetermined system of equations was solved using the least squares method, and the NO was calculated. x Concentration and NH3 concentration.

[0038] Example 3 This embodiment provides a NO x The system for simultaneous measurement of NH3 concentration includes: Excitation voltage application module, used to apply excitation voltage to NO x The sensor's first oxygen pump applies an excitation voltage; The output signal acquisition module is used to simultaneously acquire NO signals while applying the excitation voltage. x The sensor's output signal; The frequency domain feature vector acquisition module is used to perform Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal. The synchronous measurement module is used to construct and solve an overdetermined system of equations based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, to obtain NO. x The concentrations of NH3 and NH4+.

[0039] The rest is the same as in Example 1.

[0040] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A type of NO x The method for simultaneous measurement of NH3 concentration is characterized by, Includes the following steps: NO x The sensor's first oxygen pump applies an excitation voltage; While applying the excitation voltage, NO is simultaneously collected. x The sensor's output signal; Perform Fourier transforms on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal. Based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, an overdetermined system of equations is constructed and solved to obtain NO. x Concentration and NH3 concentration.

2. The NO according to claim 1 x The method for simultaneous measurement of NH3 concentration is characterized by, The NO x The sensor is a dual-chamber current-limiting amperometric sensor based on zirconium oxide solid electrolyte, including a first chamber and a second chamber. A first oxygen pump is provided in the first chamber, and a second oxygen pump and a measuring pump are provided in the second chamber.

3. The NO according to claim 2 x The method for simultaneous measurement of NH3 concentration is characterized by, The excitation voltage changes dynamically over time and is obtained by superimposing a periodic AC signal onto a DC bias voltage. The excitation voltage is: In the formula, For excitation voltage, For time, This is the DC bias voltage. It is a periodic alternating signal.

4. The NO according to claim 3 x The method for simultaneous measurement of NH3 concentration is characterized by, The frequency of the periodic AC signal is set at NO. x The sensor's electrochemical system is able to respond normally and is within the range that causes changes in the oxidation rate of NH3 on the Pt electrode.

5. The NO according to claim 4 x The method for simultaneous measurement of NH3 concentration is characterized by, The NO x The sensor's output signal is the pump current of the measuring pump, and its calculation formula is as follows: In the formula, For output signal, NO x Sensor sensitivity, NO x concentration, The concentration of NH3. The conversion of NH3 to NO x Conversion rate The surface area of ​​the Pt electrode in the first chamber used for the NH3 oxidation reaction. It is a natural exponential function. When all active sites on the Pt electrode surface are completely covered by NH3, NH3→NO x The theoretical maximum rate that the reaction can achieve. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–O bonds on the Pt electrode surface. The gas constant is... Operating temperature Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. As a competitive adsorption term, Let be the adsorption equilibrium constant of O2 on the Pt electrode surface. This represents the partial pressure of oxygen within the first chamber. This represents the theoretical maximum rate that the NH3→N2 reaction can achieve when all active sites on the Pt electrode surface are completely covered by O2. This refers to the energy barrier that NH3 molecules need to overcome to break N–H bonds and form N–N bonds on the Pt electrode surface. is the desorption rate constant.

6. The NO according to claim 5 x The method for simultaneous measurement of NH3 concentration is characterized by, The partial pressure of oxygen within the first chamber is: In the formula, This represents the partial pressure of oxygen within the first chamber. For reference oxygen partial pressure, It is a natural exponential function. It is Faraday's constant. The gas constant is... Operating temperature The excitation voltage; The competitive adsorption term is: In the formula, As a competitive adsorption term, Let be the adsorption equilibrium constant of NH3 on the Pt electrode surface. This refers to the concentration of NH3.

7. The NO according to claim 1 x The method for simultaneous measurement of NH3 concentration is characterized by, The frequency domain feature vector includes the amplitude and phase information of the signal sequence at the fundamental frequency and harmonic frequencies.

8. The NO according to claim 1 x The method for simultaneous measurement of NH3 concentration is characterized by, The overdetermined system of equations is as follows: In the formula, To obtain the frequency domain eigenvector of the output signal under the first applied excitation voltage, For the model function of support vector machines, For the frequency domain eigenvector of the first excitation voltage, NO x concentration, The concentration of NH3. To obtain the frequency domain eigenvector of the output signal under the second excitation voltage, For the frequency domain eigenvector of the second excitation voltage, To obtain the frequency domain eigenvector of the output signal under the application of the Mth excitation voltage, Let be the frequency domain eigenvector of the Mth excitation voltage; The NO x The concentration estimates of NH3 and NH4+ were obtained by fitting the solution using the least squares method, where the objective function of the least squares method is: In the formula, Let the objective function be the least squares method. The number of different excitation voltages, In the first The frequency domain eigenvector of the output signal is obtained under the application of an excitation voltage. In the first The frequency domain eigenvector of the excitation voltage, It is the vector norm.

9. The NO according to claim 8 x The method for simultaneous measurement of NH3 concentration is characterized by, Based on multiple known NO x The combined concentration of NH3 and the frequency domain eigenvectors of the excitation voltage and output signal collected under different operating conditions, along with their corresponding NO concentrations. x The actual concentration of NH3 was used to train the support vector machine through offline calibration.

10. A type of NO x The system for synchronous measurement of NH3 concentration is characterized in that, include: Excitation voltage application module, used to apply excitation voltage to NO x The sensor's first oxygen pump applies an excitation voltage; The output signal acquisition module is used to simultaneously acquire NO while the excitation voltage is applied. x The sensor's output signal; The frequency domain feature vector acquisition module is used to perform Fourier transform on the signal sequence of the excitation voltage and the signal sequence of the output signal respectively to obtain the frequency domain feature vector of the excitation voltage and the frequency domain feature vector of the output signal. The synchronous measurement module is used to construct and solve an overdetermined system of equations based on the frequency domain eigenvectors of the excitation voltage and the frequency domain eigenvectors of the output signal obtained under different excitation voltages, to obtain NO. x The concentrations of NH3 and NH4+.

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