A temperature measurement method for multi-cell oxygen sensor

Abstract

The present invention relates to a temperature measurement method for a multi-cell oxygen sensor. The multi-cell oxygen sensor comprises at least two ceramic diaphragm cells, one of which is a reference cell and the other is an oxygen pump cell. The measurement method comprises the following steps: (1) preparing a standard ceramic diaphragm cell; (2) drawing an impedance-temperature calibration curve for the standard ceramic diaphragm cell; (3) selecting any reference cell and any oxygen pump cell in the multi-cell oxygen sensor, and measuring the resistance R of any oxygen pump cell. p and the resistance R of any reference cell r ; (4) The reference battery resistance R r and the oxygen pump battery resistance R p The difference is normalized to obtain a normalized measured impedance value; the normalized measured impedance value is substituted into the fitting formula of the standard ceramic diaphragm battery impedance-temperature calibration curve to obtain the temperature of the multi-cell oxygen sensor.

Description

Technical Field

[0001] The invention belongs to the field of oxygen concentration / partial pressure detection oxygen sensors, and in particular relates to a temperature measurement method for a multi-cell oxygen sensor. Background Art

[0002] Ceramic diaphragm batteries (such as zirconia-doped oxygen ion conductors) can be composed of ceramic diaphragm batteries with electrolytes and platinum electrodes on both sides. Figure 1 (as shown in Figure 1), when the electrodes on either side of this cell are exposed to different oxygen concentrations, a Nernst potential is generated, known as a reference cell. Alternatively, the oxygen ion conductivity of the ceramic can be exploited to apply a voltage across the diaphragm, achieving directional oxygen transport, known as a pump oxygen cell. Due to their distinct functions, reference and pump oxygen cells typically have different structures. To achieve a higher pump current at a lower overvoltage, pump oxygen cells typically have a larger electrode area and a thinner electrolyte than reference cells.

[0003] In the application process, the ceramic diaphragm cell can be used alone as a reference cell or a pump oxygen cell to measure oxygen concentration, namely, a concentration-type oxygen sensor and a limiting current-type oxygen sensor. It is also possible to use multiple ceramic diaphragm cells as reference cells and pump oxygen cells respectively to control the oxygen concentration in the test cavity within a specific range, and then accurately measure the oxygen concentration or oxygen partial pressure through parameters such as limiting current and pump oxygen time. This is also the working basis of devices such as wide-band oxygen sensors, variable frequency oxygen sensors, and nitrogen oxide sensors. The structural diagrams of the above five types of oxygen sensors can be found in the appendix of the manual. Figure 2-6 Since wide-band oxygen sensors, variable-frequency oxygen sensors, nitrogen oxide sensors, and other devices are all composed of two or more ceramic diaphragm cells, the above sensors are collectively referred to as multi-cell oxygen sensors.

[0004] In principle, multi-cell oxygen sensors combine the advantages of rapid Nernst potential response and precise electrochemical oxygen transport. Compared to single-cell concentration-type or limiting current-type oxygen sensors, they offer significant advantages in response time, measurement accuracy, and measurement range. They are widely used in automotive, aviation, and other fields to accurately measure the oxygen concentration or partial pressure of the gas under test. Because the Nernst voltage of the reference cell and the oxygen pumping performance of the pumping cell are both closely related to temperature, accurately measuring the sensor temperature is a prerequisite for the application of multi-cell oxygen sensors to achieve accurate measurement of oxygen concentration or partial pressure.

[0005] The existing temperature measurement method of multi-cell oxygen sensors has problems such as inaccurate temperature measurement results, delayed measurement results and low measurement sensitivity, which need to be solved urgently. Summary of the Invention

[0006] Aiming at the problems of low accuracy, hysteresis and low sensitivity in the current temperature measurement process of a multi-cell oxygen sensor, the present invention provides a temperature measurement method for a multi-cell oxygen sensor.

[0007] Specifically, the present invention provides a temperature measurement method for a multi-cell oxygen sensor, wherein the multi-cell oxygen sensor includes at least two ceramic diaphragm cells, one of which is a reference cell and the other is an oxygen pump cell;

[0008] The measuring method comprises the following steps:

[0009] (1) Preparation of standard ceramic diaphragm batteries;

[0010] (2) Draw the impedance-temperature calibration curve of the standard ceramic diaphragm battery;

[0011] (3) Select any reference cell and any pump oxygen cell in the multi-cell oxygen sensor and measure the resistance R of any pump oxygen cell. p and the resistance R of any reference cell r ;

[0012] (4) The reference battery resistance R r and the oxygen pump battery resistance R p The difference is normalized to obtain a normalized measured impedance value; the normalized measured impedance value is substituted into the fitting formula of the standard ceramic diaphragm battery impedance-temperature calibration curve to obtain the temperature of the multi-cell oxygen sensor.

[0013] Preferably, the electrolyte material, electrode material and preparation process used in the standard ceramic diaphragm battery are consistent with those of the reference cell and pump oxygen cell in the multi-cell oxygen sensor.

[0014] Preferably, the electrolyte material is yttria-stabilized zirconia, and the electrode material is a platinum electrode, or a porous platinum and zirconia composite electrode.

[0015] Preferably, the thickness of the electrolyte of the standard ceramic diaphragm battery is the same as the thickness of the electrolyte of the reference battery of the multi-cell oxygen sensor to be tested, preferably 0.1-0.5 mm.

[0016] Preferably, the electrode area of ​​the standard ceramic diaphragm battery is the same as the electrode area of ​​the pump oxygen battery of the multi-cell oxygen sensor, preferably 1-100mm 2 .

[0017] Preferably, in step (2), the calibration method of the impedance-temperature calibration curve of the standard ceramic diaphragm battery is as follows: using a precious metal wire and a precious metal mesh with a diameter of not less than 0.5 mm to connect the electrodes on both sides of the standard battery, and using the AC impedance method to measure the battery AC impedance curve at different temperatures in a programmable temperature furnace; comparing the AC impedance curves at different temperatures, selecting the frequency in the AC impedance within the temperature range to be measured where the absolute value of the capacitive reactance is not greater than 10% of the absolute value of the impedance at the same frequency as the characteristic frequency, and plotting the impedance value and temperature value at the characteristic frequency as the horizontal and vertical coordinates, respectively, and fitting to obtain the standard battery impedance-temperature calibration theoretical formula lg(R / Ω)=b+(1000×k) / (T / ℃+273.15), wherein: R represents the standard battery impedance value, unit Ω; T represents the standard battery temperature value, unit ℃; b and k are constants independent of temperature.

[0018] Preferably, the characteristic frequency is 10 2 ~10 4 Hz, preferably 10 3 ~10 4 Hz.

[0019] Preferably, the oxygen sensor pump oxygen cell impedance R p and reference cell impedance R r The measurement method can be selected from the following two methods: using a frequency of 10 3 ~10 4 Hz, an alternating current with an amplitude of 1 to 10uA is used as the excitation source, and the corresponding voltage value is measured to obtain the battery impedance value; or, a frequency of 10 3 ~10 4 An alternating voltage with an amplitude of 1 to 100 mV is used as the excitation source, and the corresponding current value is measured to obtain the battery impedance value.

[0020] Preferably, the normalized measurement impedance R=the difference between the reference cell impedance value and the pump oxygen cell impedance value divided by the normalization coefficient C, the normalization coefficient C=B-1 / A, the ratio of the reference cell electrolyte thickness of the oxygen sensor to the pump oxygen cell electrolyte thickness is set to A, and the ratio of the pump oxygen cell electrode area of ​​the oxygen sensor to the reference cell electrode area is set to B.

[0021] Beneficial effects

[0022] The present invention prepares a standard cell with the same electrolyte and electrode materials as the sensor. Based on the Arrhenius relationship between electrolyte conductivity and temperature, a standard cell impedance-temperature calibration curve and theoretical formula are drawn for sensor temperature measurement. This measurement method is universally applicable. The input value is the impedance value measured by the AC impedance method. By optimizing the measurement frequency, the measured impedance value is independent of the battery current and voltage loading state, ensuring that the impedance values ​​measured under the operating conditions of the pumped oxygen cell and reference cell are comparable with the impedance values ​​of the standard cell.

[0023] The sensor temperature is measured using the impedance values ​​of the oxygen pump cell and the reference cell. Since these two impedance values ​​directly reflect the sensor operating temperature, hysteresis during temperature testing can be avoided. The difference between the two values ​​is used to remove the influence of the platinum lead wire during measurement, further reducing errors caused by the platinum lead wire. This ensures that the resistance difference maintains the same sensitivity to temperature changes, meaning that the calibration curve has a wider applicable temperature range.

[0024] In addition, the normalization process makes the measured resistance value only related to the sensor temperature. There is no need to substitute parameters such as electrode area and electrolyte thickness. The sensor temperature can be obtained by directly comparing with the calibration curve or substituting it into the theoretical formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the ceramic diaphragm battery structure;

[0026] Figure 2 Schematic diagram of the structure and impedance measurement of the concentration-differential oxygen sensor;

[0027] Figure 3 Schematic diagram of the limiting current oxygen sensor structure and impedance measurement;

[0028] Figure 4 Schematic diagram of the wide-band oxygen sensor structure and the impedance measurement of the pump oxygen cell and reference cell;

[0029] Figure 5 It is a schematic diagram of the frequency conversion oxygen sensor structure and the impedance measurement of the pump oxygen cell and reference cell;

[0030] Figure 6 Schematic diagram of the NOx sensor structure and the impedance measurement of the pump oxygen cell and reference cell;

[0031] Figure 7 The AC impedance curves at different temperatures for the standard ceramic diaphragm battery used in the embodiment are shown in Figure 1. The arrows indicate the impedance value at 1000 Hz.

[0032] Figure 8The AC impedance curves of the standard ceramic diaphragm battery used for calibration in the examples are as follows: no voltage loading (square points), 100 mV voltage loading (circular points), and 5 μA current loading mode (triangle points);

[0033] Figure 9 This is the impedance-temperature calibration curve at 1000 Hz of the standard ceramic diaphragm battery used for calibration in the embodiment;

[0034] Figure 10 The actual temperature value (square point) corresponding to the normalized impedance value in the embodiment, the theoretical temperature value (circular point) calculated according to the calibration curve, and the difference between the two (cross point);

[0035] Figure 11 The actual temperature value (square point) corresponding to the normalized impedance value in the comparative example, the theoretical temperature value (circular point) calculated according to the calibration curve, and the difference between the two (cross point). DETAILED DESCRIPTION

[0036] The present invention is further described by way of embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.

[0037] Temperature has a significant effect on the conductivity of ceramic electrolytes, which in turn affects the impedance of ceramic diaphragm batteries. Therefore, the sensor temperature can be obtained by measuring the impedance. In a specific implementation, the impedance-temperature calibration curve and fitting formula of the standard battery can be used to input the impedance value to obtain the sensor temperature value. In calibration and measurement, the impedance value can be obtained by the AC impedance method at a specific frequency. By optimizing the frequency value, the influence of the current and voltage loading state on the impedance value can be avoided, ensuring that the reference cell, pump oxygen cell impedance and standard cell impedance are comparable. At the same time, the impedance value measured during the measurement process adopts the difference between the reference cell impedance value and the pump oxygen cell impedance value after normalization. Since the impedance of the reference cell and the pump oxygen cell are both composed of the cell impedance and the lead impedance, and the reference cell and the pump oxygen cell are usually designed with a common lead, the difference processing can remove the lead influence. The difference is further normalized and can be easily compared with the calibration curve to obtain the sensor temperature.

[0038] Based on the above principles, the present invention provides a temperature measurement method for a multi-cell oxygen sensor. The measurement method may include the following steps.

[0039] (1) Preparation of standard ceramic diaphragm batteries (also called "standard batteries").

[0040] The structural diagram of the standard battery is as follows Figure 1As shown, the preparation process of the standard battery can adopt conventional technical means in this field. A standard ceramic diaphragm battery consisting of bilaterally symmetrical electrodes and a dense electrolyte is prepared by processes such as casting, printing, isostatic pressing, cutting, and sintering. In addition, the electrolyte material and electrode material used in the control standard battery and the sintering treatment parameters are completely consistent with the preparation of the reference cell and the pump oxygen cell in the multi-cell oxygen sensor. In some embodiments, the electrolyte material can be yttria-stabilized zirconia (YSZ); the electrode material can be a platinum electrode, or a porous platinum and zirconia composite electrode.

[0041] In some embodiments, the thickness of the standard cell electrolyte can be controlled to be the same as the thickness of the reference cell electrolyte of the multi-cell oxygen sensor, preferably 0.1-0.5 mm; the area of ​​the standard cell electrode can be controlled to be the same as the area of ​​the pump oxygen cell electrode of the multi-cell oxygen sensor, preferably 1-100 mm 2 Considering the operability of drawing the calibration curve of the standard battery, when the thickness of the reference battery electrolyte is less than 0.1mm or the electrode area of ​​the pump oxygen battery is less than 1mm 2 When the reference cell electrolyte thickness is greater than 0.5 mm or the oxygen pump cell electrode area is greater than 100 mm 2 When the standard battery electrolyte thickness and electrode area can be proportionally increased or proportionally decreased to the preferred range.

[0042] The electrolyte thickness and electrode area of ​​the standard cell are set as described above, primarily to ensure that the test data, after simple normalization, can be directly compared with the calibration curve described below to obtain the temperature of the multi-cell oxygen sensor. Generally, in a multi-cell oxygen sensor, the diaphragm thickness of the pump oxygen cell is thinner and the electrode area is larger than that of the reference cell. The present invention controls the electrolyte thickness of the standard cell to be the same as that of the reference cell, but thicker than that of the pump oxygen cell. This reduces the relative error in thickness measurement and, furthermore, the thicker electrolyte offers greater strength and ease of operation. The electrode area is the same as that of the pump oxygen cell, but larger than that of the reference cell, reducing the relative error in area measurement and improving the accuracy of resistance measurements.

[0043] (2) Draw the impedance-temperature calibration curve of the standard ceramic diaphragm battery.

[0044] The impedance of the standard ceramic diaphragm battery prepared according to step (1) is measured using the AC impedance method, and a standard battery impedance-temperature calibration curve is drawn based on the Arrhenius relationship between electrolyte conductivity and temperature. The impedance-temperature theoretical relationship of the standard battery is shown in Formula 1, wherein the electrolyte thickness of the standard battery is the same as that of the reference cell of the multi-cell oxygen sensor, and the electrode area is the same as that of the pump oxygen cell of the multi-cell oxygen sensor.

[0045]

[0046] Where: R represents the standard battery impedance value, unit is Ω; T represents the standard battery temperature value, unit is °C; b and k are constants that are independent of temperature.

[0047] In the calibration curve measurement, a precious metal wire and a precious metal mesh with a diameter of not less than 0.5 mm can be used to connect the electrodes on both sides of the standard battery. The precious metal can be gold, silver, or platinum. The battery AC impedance curve at different temperatures is measured using the AC impedance method in a programmable temperature furnace. Comparing the AC impedance curves at different temperatures, the frequency at which the absolute value of the capacitive reactance (imaginary part) in the AC impedance within the temperature range to be measured is selected as the characteristic frequency. The impedance (real part) value and temperature value at the characteristic frequency are plotted as the horizontal and vertical coordinates, respectively, and the standard battery impedance-temperature calibration theoretical formula is obtained by fitting.

[0048] In an optional embodiment, the characteristic frequency of the impedance measurement can be controlled to be 10 2 ~10 4 Hz, preferably 10 3 ~10 4 The above frequency range is selected mainly because the frequency with the smallest absolute value of capacitive reactance in AC impedance occurs within the normal operating temperature range of 500-800℃.

[0049] (3) Select any reference cell and any pump oxygen cell in the multi-cell oxygen sensor and measure the impedance R of any pump oxygen cell p and the impedance R of any reference cell r (See attached test diagram Figure 2-6 ).

[0050] The multi-cell oxygen sensor includes at least two ceramic diaphragm cells, one of which serves as a reference cell and the other as a pumping oxygen cell. The reference cell has a larger electrolyte thickness to electrode area ratio, while the pumping oxygen cell has a smaller electrolyte thickness to electrode area ratio. Any reference cell or any pumping oxygen cell in the multi-cell oxygen sensor can be selected for impedance measurement.

[0051] Taking the variable frequency oxygen sensor as an example, its structure and the schematic diagram of the impedance measurement of the pump oxygen cell and reference cell are shown in the figure. Figure 5 As shown. Among them, the impedance value of the oxygen pump cell R p and the reference cell impedance R r The AC impedance method is used for measurement. During the test, the alternating voltage can be selected as the excitation source, and the alternating voltage frequency can be selected as 10 3 ~10 4Hz, select the amplitude of 1~100mV, measure the corresponding current value, and you can get the battery impedance value; you can also choose alternating current as the excitation source, and select the alternating current frequency of 10 3 ~10 4 Hz, select the amplitude from 1 to 10uA, measure the corresponding voltage value, and you can get the battery impedance value.

[0052] The oxygen pump cell and the reference cell impedance value test circuits are two independent circuits or are connected in parallel using a common ground line.

[0053] Among them, the oxygen pump cell impedance R p , reference cell impedance R r The relationship between the electrolyte resistivity ρ, thickness T and electrode area S is as follows:

[0054]

[0055]

[0056] (4) The reference cell impedance R r and the oxygen pump cell impedance R p The measured impedance value after normalization of the difference (input value) is compared with the calibration curve to determine the temperature of the multi-cell oxygen sensor.

[0057] According to the above formulas (1)-(3), we can know that:

[0058]

[0059]

[0060] The above formulas (1)-(5) show that theoretically, the sensor temperature can be obtained by taking the resistance difference between the reference cell and the pump oxygen cell of the multi-cell oxygen sensor as input and drawing a calibration curve based on the standard cell.

[0061] The normalization method is to divide the difference between the reference cell impedance and the pump oxygen cell impedance by the normalization coefficient C, where C = B-1 / A. The ratio of the reference cell electrolyte thickness to the pump oxygen cell electrolyte thickness of the oxygen sensor is set to A, and the ratio of the pump oxygen cell electrode area to the reference cell electrode area of ​​the oxygen sensor is set to B. This method allows the measured value to be directly compared with the calibration curve to obtain the sensor temperature.

[0062] The present invention utilizes the impedance of the pump oxygen cell and the reference cell of a multi-cell oxygen sensor to measure temperature. Since the pump oxygen cell and the reference cell represent the sensor's core operating area, their resistance is directly related to the sensor's operating area temperature, eliminating hysteresis during temperature testing. Furthermore, the difference between the two is used during measurement to further mitigate errors introduced by platinum leads, ensuring that this resistance difference remains sensitive to temperature changes. Furthermore, normalization facilitates temperature comparisons between different sensors.

[0063] The following examples are further listed to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range. That is, those skilled in the art can make selections within a suitable range based on the description herein, and are not limited to the specific values ​​​​exemplified below.

[0064] Example

[0065] (1) Preparation of standard ceramic diaphragm batteries.

[0066] A standard ceramic diaphragm cell consisting of bilaterally symmetrical platinum electrodes and a dense yttria-stabilized zirconia electrolyte was prepared by tape casting, printing, isostatic pressing, and cutting. The electrolyte thickness was 0.2 mm, the same as the reference cell electrolyte thickness of the multi-cell oxygen sensor to be tested; the electrode area was 24 mm 2 , which is the same as the electrode area of ​​the oxygen pump cell of the variable frequency oxygen sensor to be tested.

[0067] (2) Draw the impedance-temperature calibration curve of the standard ceramic diaphragm battery.

[0068] Using a 0.5mm diameter silver wire and silver mesh to connect the platinum electrodes on both sides, the AC impedance curve of the battery was measured at a characteristic frequency of 1000Hz and a temperature range of 530°C-865°C using the AC impedance method in a programmable temperature furnace. The logarithm of the impedance and the inverse of the temperature were plotted as the horizontal and vertical axes, respectively, and a standard battery impedance-temperature calibration curve was obtained by fitting.

[0069] Figure 7 The following is the AC impedance curve of the standard ceramic diaphragm battery used for calibration in the examples at different temperatures. The arrows indicate the impedance value at 1000Hz. Each point in the figure represents the AC impedance value of the battery at different frequencies, with the vertical axis representing the capacitive reactance value and the horizontal axis representing the impedance value. As can be seen from the figure, when the temperature is between 500-700°C and the frequency is 1000Hz, the absolute value of the capacitive reactance value on the vertical axis is relatively small (the absolute value of the capacitive reactance is no more than 10% of the absolute value of the impedance at the same frequency). Therefore, 1000Hz was selected as the characteristic frequency of the calibration curve.

[0070] Figure 8 Figure 2 shows the AC impedance curves of the standard ceramic diaphragm battery used for calibration in the examples under no voltage loading (square points), 100mV voltage loading (circular points), and 5μA current loading modes (triangle points). As can be seen from the figure, the impedance value at the 1000Hz characteristic frequency remains almost unchanged under different current and voltage loading modes, while the 100mV voltage and 5μA current loading conditions are close to the operating conditions of the reference cell and the pumped oxygen cell, indicating that the impedance values ​​of the reference cell and the pumped oxygen cell measured at this characteristic frequency are comparable to those of the standard cell (calibrated at 0V voltage).

[0071] Figure 9 This is the impedance-temperature calibration curve at 1000 Hz for a standard ceramic diaphragm battery used in the examples. The vertical axis represents temperature, the horizontal axis represents impedance, and the square dots represent measured values. The formula marked in the figure is the theoretical impedance-temperature formula obtained after fitting.

[0072] (3) Using the AC impedance method to measure the pump oxygen cell resistance R of the variable frequency oxygen sensor under test at 1000 Hz p and the reference cell resistance R r .

[0073] like Figure 5 The figure shows the structure of the variable frequency oxygen sensor to be tested and the impedance measurement diagram of the pump oxygen cell and reference cell in this embodiment. As shown in the figure, the impedance test circuits of the two cells in this embodiment are connected in parallel with a common ground line.

[0074] The variable frequency oxygen sensor pump oxygen battery impedance R p The measurement method is as follows: use an alternating current with a frequency of 1000Hz and an amplitude of 1uA as the excitation source, measure the corresponding voltage value, and obtain the battery impedance value.

[0075] The reference battery impedance R of the variable frequency oxygen sensor to be measured r The measurement method is as follows: use an alternating voltage with a frequency of 1000 Hz and an amplitude of 20 mV as the excitation source, measure the corresponding current value, and obtain the battery impedance value.

[0076] (4) According to the thickness of the oxygen pump battery electrolyte of 0.1mm and the thickness of the reference battery electrolyte of 0.2mm, the A value is 2; according to the electrode area of ​​the oxygen pump battery of 24mm 2 、Reference cell electrode area 6mm 2 , and the B value is 4; according to the A and B values, the normalization coefficient C = (B-1 / A) is determined to be 3.5.

[0077] The variable frequency oxygen sensor pump oxygen battery resistance R p and the reference cell resistance Rr The difference is divided by the normalization coefficient C, and the measured impedance value after normalization is compared with the calibration curve. The normalized measured impedance R is substituted into the impedance-temperature theoretical formula obtained after the above fitting to determine the temperature value of the variable frequency oxygen sensor to be measured.

[0078] Figure 10 The following plots represent the actual temperature corresponding to the normalized impedance value in the embodiment (square points), the theoretical temperature calculated according to the calibration curve (circular points), and the difference between the two (cross points). As can be seen from the figure, the difference between the actual temperature value and the calculated theoretical temperature value is less than 3°C, indicating a close approximation. This demonstrates that the patented method can achieve accurate temperature measurement for variable frequency oxygen sensors.

[0079] Comparative Example

[0080] This comparative example refers to the embodiment, the main difference is that the AC impedance method is used to measure the pump oxygen cell impedance R of the oxygen sensor at 1000Hz p At the same time, according to the oxygen pump battery electrode area of ​​24mm 2 , Pump oxygen battery electrolyte thickness 0.1mm; Standard battery electrode area 24mm 2 , the electrolyte thickness is 0.2 mm, and the normalized coefficient D value (standard battery electrolyte thickness / oxygen pump battery electrolyte thickness) is 2.

[0081] The comparative example directly uses the resistance of the oxygen pump cell as the input value, which is different from the embodiment in which the difference between the oxygen pump cell and the reference cell is used as the input value. Therefore, under the premise that the lead resistance can be ignored, the resistance difference between the oxygen pump cell and the standard cell here only comes from the difference in electrolyte thickness, that is, the normalization coefficient D (standard cell electrolyte thickness / pump cell electrolyte thickness) is 2. p Multiply the normalized measured value by the coefficient D and compare it with the calibration curve to determine the temperature value of the sensor to be measured.

[0082] In this comparative example, the impedance of the oxygen pump cell is directly used for temperature measurement, and the input impedance is not differentiated and the normalization processing method used is different from that of the embodiment. Figure 11 The actual temperature values ​​corresponding to the normalized impedance values ​​in the comparative example (square points), the theoretical temperature values ​​calculated according to the calibration curve (circular points), and the difference between the two (cross points) are shown. As can be seen from the figure, compared to the temperature differences in the embodiment, which are all less than 3°C in the range of 530-810°C, the temperature values ​​obtained using only the impedance of the oxygen pump cell have a small deviation at high temperatures, but the temperature deviation increases rapidly as the temperature decreases.

[0083] It can be seen from the examples and comparative examples that the accuracy of impedance temperature measurement can be greatly improved by processing and normalizing the difference in impedance between the oxygen pump cell and the reference cell.

[0084] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for measuring temperature of a multi-cell oxygen sensor, characterized in that: The multi-cell oxygen sensor includes at least two ceramic diaphragm cells, one of which is a reference cell and the other is an oxygen pump cell; The measuring method comprises the following steps: (1) Preparation of standard ceramic diaphragm batteries; (2) Draw the impedance-temperature calibration curve of the standard ceramic diaphragm battery; (3) Select any reference cell and any pump oxygen cell in the multi-cell oxygen sensor and measure the resistance R of any pump oxygen cell. p and the resistance R of any reference cell r ; (4) The resistance value of the reference battery R r and the resistance value R of the oxygen pump battery p Normalize the difference between the measured impedance and the impedance value to obtain a normalized measured impedance value; substitute the normalized measured impedance value into the fitting formula of the standard ceramic diaphragm battery impedance-temperature calibration curve to obtain the temperature of the multi-cell oxygen sensor; The electrolyte thickness of the standard ceramic diaphragm cell is the same as the electrolyte thickness of the reference cell in the multi-cell oxygen sensor; The electrode area of ​​the standard ceramic diaphragm cell is the same as the electrode area of ​​the pump oxygen cell in the multi-cell oxygen sensor; The normalized measured impedance value = the difference between the resistance of the reference cell and the resistance of the pump oxygen cell divided by the normalization coefficient C, the normalization coefficient C = B-1 / A, the ratio of the electrolyte thickness of the reference cell of the oxygen sensor to the electrolyte thickness of the pump oxygen cell is set to A, and the ratio of the electrode area of ​​the pump oxygen cell of the oxygen sensor to the electrode area of ​​the reference cell is set to B.

2. The measuring method according to claim 1, wherein The electrolyte material, electrode material and preparation process used in the standard ceramic diaphragm battery are consistent with those of the reference cell and pump oxygen cell in the multi-cell oxygen sensor.

3. The measuring method according to claim 2, characterized in that The electrolyte material is yttria-stabilized zirconia, and the electrode material is a platinum electrode or a porous platinum and zirconia composite electrode.

4. The measuring method according to claim 1, wherein The electrolyte thickness of the standard ceramic diaphragm battery and the electrolyte thickness of the reference battery in the multi-cell oxygen sensor are both 0.1-0.5 mm.

5. The measuring method according to claim 1, wherein: The electrode area of ​​the standard ceramic diaphragm battery and the electrode area of ​​the pump oxygen cell in the multi-cell oxygen sensor are both 1-100mm 2 .

6. The measuring method according to claim 1, characterized in that In step (2), the calibration method of the impedance-temperature calibration curve of the standard ceramic diaphragm battery is as follows: using a precious metal wire and a precious metal mesh with a diameter of not less than 0.5 mm to connect the electrodes on both sides of the standard battery, and using the AC impedance method to measure the battery AC impedance curve at different temperatures in a programmable temperature furnace; comparing the AC impedance curves at different temperatures, selecting the frequency in the AC impedance within the temperature range to be measured where the absolute value of the capacitive reactance is not greater than 10% of the absolute value of the impedance at the same frequency as the characteristic frequency, plotting the impedance value and temperature value at the characteristic frequency as the horizontal and vertical coordinates, respectively, and fitting to obtain the standard battery impedance-temperature calibration theoretical formula lg (R / Ω) = b + (1000×k) / (T / ℃ + 273.15), wherein: R represents the standard battery impedance value, unit Ω; T represents the standard battery temperature value, unit ℃; b and k are constants independent of temperature.

7. The measuring method according to claim 6, characterized in that The characteristic frequency is 10 2 ~10 4 Hz.

8. The measuring method according to claim 6, characterized in that The characteristic frequency is 10 3 ~10 4 Hz.

9. The measuring method according to claim 1, wherein: The resistance value R of the multi-cell oxygen sensor pump oxygen cell p And the resistance of the reference cell R r The measurement method can be selected from the following two methods: using a frequency of 10 3 ~10 4 Hz, an alternating current with an amplitude of 1 to 10uA is used as the excitation source, and the corresponding voltage value is measured to obtain the battery resistance value; or, a frequency of 10 3 ~10 4 An alternating voltage with an amplitude of 1 to 100 mV is used as the excitation source, and the corresponding current value is measured to obtain the battery resistance.

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