Ammonium sulfate ph calculation method based on electrochemical principle and temperature compensation technology

Abstract

The application relates to the technical field of electrochemical detection, and specifically discloses an ammonium sulfate PH calculation method based on an electrochemical principle and a temperature compensation technology, which comprises the following steps: collecting a non-standard state electrode potential signal and an NTC thermistor real-time resistance signal of an ammonium sulfate solution to be measured; using an improved temperature fitting algorithm based on a temperature-resistance nonlinear relationship and an optimized fitting process to convert an actual thermodynamic temperature of the solution; combining the actual thermodynamic temperature to compensate the non-standard state electrode potential signal, eliminating the interference of temperature change on the potential measurement; and substituting the compensated electrode potential value and the thermodynamic temperature into a simplified expression of the Nernst equation to inversely solve the hydrogen ion concentration, and then obtaining the final PH value of the ammonium sulfate solution through negative logarithm operation. The method optimizes the temperature fitting precision and the electrode potential compensation adaptability, and improves the PH measurement deviation problem of the ammonium sulfate solution.

Description

Technical Field

[0001] This invention relates to the field of electrochemical detection technology, specifically to a method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology. Background Technology

[0002] Conventional pH measurements of ammonium sulfate solutions often employ an electrochemical electrode detection method combined with simplified temperature acquisition. The temperature acquisition stage typically uses linear fitting to process the resistance signal from the NTC thermistor, failing to consider the intrinsic relationship between the thermistor's characteristic resistance value and thermodynamic temperature to construct a computational model, nor does it finely adjust or optimize the fitting process. The electrode potential signal processing stage generally uses a universal compensation mode, without distinguishing between standard and non-standard state electrode potential signals. Temperature compensation parameters remain fixed, and the hydrogen ion concentration is calculated directly using the complete Nernst equation.

[0003] Linear fitting methods cannot accurately capture the nonlinear changes in the resistance of NTC thermistors with thermodynamic temperature. The temperature fitting calculation process is prone to inherent biases, leading to discrepancies between the calculated solution temperature and the actual operating conditions. Fixed-parameter general temperature compensation modes cannot adapt to real-time thermodynamic temperature changes in terms of compensation magnitude, making it difficult to offset the impact of temperature fluctuations on non-standard electrode potential measurements. The complete Nernst equation contains numerous redundant calculation parameters, amplifying deviations in temperature measurement and potential compensation. These deviations, when cumulative, distort the calculation of hydrogen ion concentration in ammonium sulfate solution, ultimately reducing the accuracy of pH calculations. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology, so as to solve the aforementioned background problems.

[0005] The objective of this invention can be achieved through the following technical solutions: Ammonium sulfate pH calculation methods based on electrochemical principles and temperature compensation technology include: Acquire the non-standard state electrode potential signal of the ammonium sulfate solution to be tested and the real-time resistance signal of the NTC thermistor; An improved temperature fitting algorithm is applied to the real-time resistance signal of the NTC thermistor to calculate the actual thermodynamic temperature of the solution. The improved temperature fitting algorithm is based on the nonlinear relationship between the resistance value of the feature point and the thermodynamic temperature, and reduces the temperature measurement error by optimizing the fitting process. Based on the actual thermodynamic temperature of the solution, temperature compensation processing is performed on the non-standard state electrode potential signal to correct the influence of thermodynamic temperature change on the electrode potential measurement value, and the compensated electrode potential value is obtained. Substituting the compensated electrode potential value and the actual thermodynamic temperature of the solution into the simplified expression of the Nernst equation, the hydrogen ion concentration in the ammonium sulfate solution is obtained by inverse solution. The final pH value of the ammonium sulfate solution to be tested is calculated using negative logarithmic operations based on the hydrogen ion concentration.

[0006] As a further aspect of the present invention, an improved temperature fitting algorithm is applied to the real-time resistance signal of the NTC thermistor to calculate the actual thermodynamic temperature of the solution, including: Under standard constant temperature conditions, the resistance values ​​of the NTC thermistor were measured at two characteristic temperature points, 25 degrees Celsius and 80 degrees Celsius, and recorded as a set of characteristic point resistance values. Based on the set of resistance values ​​at the feature points, the improved temperature fitting algorithm is called to calculate the B-value parameter of the NTC thermistor. The improved temperature fitting algorithm optimizes the B-value fitting result by taking the average value of multiple measurements. Using the calculated B-value parameter, a complete resistance-temperature correspondence data table is constructed, which covers a temperature range of 25 degrees Celsius to 80 degrees Celsius. By querying the resistance-temperature correspondence data table, the measured real-time resistance signal is mapped to the corresponding actual thermodynamic temperature of the solution.

[0007] As a further aspect of the present invention, the method of taking the average value of multiple measurements specifically involves independently repeating the measurement at least three times under the same environmental conditions, with each measurement including the complete acquisition of resistance values ​​at two characteristic temperature points.

[0008] As a further aspect of the present invention, based on the actual thermodynamic temperature of the solution, temperature compensation processing is performed on the non-standard state electrode potential signal to correct the influence of thermodynamic temperature changes on the electrode potential measurement value, including: Read the original measured value of the non-standard state electrode potential signal; Based on the theoretical relationship between temperature and electrode potential in the Nernst equation, calculate the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the solution described above. A temperature compensation coefficient is generated based on the calculated change in the theoretical slope of the electrode potential. The temperature compensation coefficient is applied to the original measured value of the non-standard state electrode potential signal, and the compensated electrode potential value is obtained through linear correction.

[0009] As a further aspect of the present invention, the compensated electrode potential value and the actual thermodynamic temperature of the solution are substituted into the simplified expression of the Nernst equation to solve for the hydrogen ion concentration in the ammonium sulfate solution, including: Obtain the standard electrode potential, ideal gas constant, Faraday constant, and the number of electrons transferred in the electrode reaction; Substitute the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction into the simplified expression of the Nernst equation for hydrogen ions. By performing algebraic transformations on the expression after substitution, the hydrogen ion concentration is separated from one side of the equation as an unknown. The hydrogen ion concentration in the ammonium sulfate solution can be directly calculated by solving the algebraically transformed equation through exponential operations.

[0010] As a further aspect of the present invention, based on the set of feature point resistance values, the improved temperature fitting algorithm is invoked to calculate the B-value parameter of the NTC thermistor, including: The nominal resistance value measured at 25 degrees Celsius is read from the set of characteristic point resistance values ​​and recorded as the first characteristic resistance. The actual resistance value measured at 80 degrees Celsius is read and recorded as the second characteristic resistance. Convert 25 degrees Celsius and 80 degrees Celsius to their corresponding first and second thermodynamic temperatures, respectively. Substitute the first characteristic resistance, the second characteristic resistance, the first thermodynamic temperature, and the second thermodynamic temperature into the B-value calculation formula for the NTC thermistor, and perform a single B-value fitting operation to obtain the preliminary B-value. By changing the ammonium sulfate solution sample or repeating the isothermal measurement process, the single B-value fitting calculation is performed multiple times to obtain multiple preliminary B-values. Calculate the arithmetic mean of all preliminary B values, and determine this arithmetic mean as the final B value parameter used to construct the resistance-temperature relationship.

[0011] As a further aspect of the present invention, the step of constructing a complete resistance-temperature correspondence data table using the calculated B-value parameter includes: Set the starting temperature, ending temperature, and temperature step value to generate a series of temperature gradient points in the range of 25 to 80 degrees Celsius. Convert each temperature gradient point to its corresponding thermodynamic temperature; Substitute the first characteristic resistor, the final B value parameter, and the thermodynamic temperature corresponding to each temperature gradient point into the resistance calculation formula of the NTC thermistor to calculate the theoretical resistance value at each temperature gradient point. A mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table.

[0012] As a further aspect of the present invention, the calculation of the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the solution, based on the theoretical relationship between temperature and electrode potential in the Nernst equation, includes: The standard temperature condition is set to 25 degrees Celsius and converted to standard thermodynamic temperature. Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the stated standard thermodynamic temperature, and denote it as the first theoretical slope; Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the actual thermodynamic temperature of the solution described above, and denote it as the second theoretical slope; Calculate the difference between the second theoretical slope and the first theoretical slope, and use this difference as the change in the theoretical slope of the electrode potential caused by temperature change.

[0013] As a further aspect of the present invention, the hydrogen ion concentration in the ammonium sulfate solution is directly calculated by solving the algebraically transformed equation through exponential operations, including: Starting from the simplified expression of the Nernst equation after substituting the standard electrode potential, ideal gas constant, Faraday constant, number of electrons transferred in the electrode reaction, compensated electrode potential value, and actual thermodynamic temperature of the solution, exponential operations with the natural constant e are performed on both sides of the equation simultaneously. After performing the exponential operation, the logarithmic term containing the hydrogen ion concentration is eliminated, resulting in an exponential equation with the hydrogen ion concentration as the unknown. Calculate the value of the exponential expression on the right side of the exponential form equation, which consists of the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction. Taking the reciprocal of the numerical value of the exponential expression yields the specific numerical value of the hydrogen ion concentration in the ammonium sulfate solution.

[0014] As a further aspect of the present invention, after constructing the resistance-temperature correspondence data table, the method further includes verifying the accuracy of the data table: The ammonium sulfate solution was sequentially adjusted to the temperature gradient points recorded in the data table using a constant temperature device. At each temperature gradient point, after the solution temperature stabilizes, use a multimeter to measure the actual resistance value of the NTC thermistor. The measured actual resistance value is compared with the theoretical resistance value recorded in the data table, and the absolute error and relative error rate are calculated. If the relative error rate at any temperature gradient point exceeds the preset threshold, the calculation of the B-value parameter and the construction process of the data table are re-executed until the relative error rates at all temperature gradient points meet the preset accuracy requirements.

[0015] Advantages of the present invention: A non-linear correspondence relationship between the characteristic point resistance value and the thermodynamic temperature is established, the temperature fitting operation process is optimized, adapted to the change law of the NTC thermistor's own resistance parameter with temperature, changing the inherent limitation of the conventional linear fitting operation mode, and reducing the numerical deviation generated in the temperature fitting process. The operation process of converting the resistance signal into the thermodynamic temperature is more in line with the actual change law, the error generated in the temperature measurement link is effectively controlled, the calculated thermodynamic temperature parameter can fit the real environmental state of the ammonium sulfate solution, restricting the numerical fluctuation range of the temperature parameter, and reducing the deviation conduction of the temperature measurement to subsequent operation steps such as electrode potential compensation and ion concentration solution, maintaining the stable output of the precondition parameters for electrochemical detection.

[0016] Based on the real-time thermodynamic temperature, temperature compensation processing is carried out on the non-standard state electrode potential signal, adapting to the influence of the dynamic change of temperature on the measured value of the electrode potential, and calming the offset of the measured value of the electrode potential caused by temperature fluctuations. Substituting the compensated electrode potential value and the thermodynamic temperature parameter into the simplified expression of the Nernst equation for calculation, streamlining the redundant operation parameters inside the equation, reducing the error accumulation in the multi-parameter linkage operation process, making the deduction operation of the hydrogen ion concentration conform to the basic operation logic of electrochemistry, weakening the numerical deviation brought by multiple operation links, and keeping the operation parameter of the hydrogen ion concentration in a stable state, and completing the negative logarithm operation conversion from the hydrogen ion concentration to the pH value relying on the continuous and accurate operation logic. Description of the drawings

[0017] The present invention will be further described below in conjunction with the drawings.

[0018] Figure 1 is the flow chart of the ammonium sulfate PH calculation method based on the electrochemical principle and temperature compensation technology described in the present invention; Figure 2 is the flow chart of the method for calculating the actual thermodynamic temperature by performing an improved temperature fitting algorithm on the NTC thermistor signal; Figure 3 is the flow chart of the calculation of the hydrogen ion concentration in the ammonium sulfate solution. Detailed implementation manners

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] See Figure 1 This invention provides a method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology, comprising: A method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology involves acquiring the non-standard state electrode potential signal of the ammonium sulfate solution to be tested and the real-time resistance signal of an NTC thermistor. An improved temperature fitting algorithm is applied to the real-time resistance signal of the NTC thermistor to calculate the actual thermodynamic temperature of the solution. This improved temperature fitting algorithm is based on the non-linear relationship between the characteristic point resistance value and the thermodynamic temperature, and reduces temperature measurement errors by optimizing the fitting process. Based on the actual thermodynamic temperature of the solution, temperature compensation processing is performed on the non-standard state electrode potential signal to correct the influence of thermodynamic temperature changes on the electrode potential measurement value, resulting in a compensated electrode potential value. The compensated electrode potential value and the actual thermodynamic temperature of the solution are substituted into the Nernst equation to simplify the expression, and the hydrogen ion concentration in the ammonium sulfate solution is solved by inverse problem. Based on the hydrogen ion concentration, the final pH value of the ammonium sulfate solution to be tested is calculated using negative logarithmic calculation.

[0021] In one embodiment of the present invention, see [reference] Figure 2 Under standard constant temperature conditions, the resistance values ​​of the NTC thermistor at two characteristic temperature points, 25 degrees Celsius and 80 degrees Celsius, were measured and recorded as a set of characteristic point resistance values. The measurement process used a high-precision constant temperature bath to control the temperature. The NTC thermistor was completely immersed in the deionized water in the constant temperature bath. After the temperature stabilized, the resistance value was read using a digital multimeter. The measurement was independently repeated 3 times under the same environmental conditions. Each measurement included the complete acquisition of the resistance values ​​at the two characteristic temperature points. The arithmetic mean of the resistance values ​​at 25 degrees Celsius obtained from the three measurements was taken as the first characteristic resistance, and the arithmetic mean of the resistance values ​​at 80 degrees Celsius obtained from the three measurements was taken as the second characteristic resistance.

[0022] Based on the set of characteristic point resistance values, the improved temperature fitting algorithm is used to calculate the B-value parameter of the NTC thermistor. The first characteristic resistance, the second characteristic resistance, the first thermodynamic temperature converted from 25 degrees Celsius, and the second thermodynamic temperature converted from 80 degrees Celsius are substituted into the B-value calculation formula of the NTC thermistor to perform a single B-value fitting operation to obtain a preliminary B-value. The ammonium sulfate solution sample is replaced and the isothermal measurement process is repeated. The single B-value fitting operation is performed 5 times to obtain 5 preliminary B-values. The arithmetic mean of all preliminary B-values ​​is calculated, and this arithmetic mean is determined as the final B-value parameter used to construct the resistance-temperature relationship. Using the calculated final B-value parameter, a complete resistance-temperature correspondence data table is constructed.

[0023] The starting temperature is set to 25 degrees Celsius, the ending temperature to 80 degrees Celsius, and the temperature step value to 1 degree Celsius. A series of temperature gradient points are generated within the range of 25 degrees Celsius to 80 degrees Celsius. Each temperature gradient point is converted into its corresponding thermodynamic temperature. The first characteristic resistance, the final B-value parameter, and the thermodynamic temperature corresponding to each temperature gradient point are substituted into the resistance calculation formula of the NTC thermistor to calculate the theoretical resistance value at each temperature gradient point. A mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table. By querying the resistance-temperature correspondence data table, the measured real-time resistance signal is mapped to the corresponding actual thermodynamic temperature of the solution.

[0024] In practical implementation, taking the online monitoring of the pH value of ammonium sulfate crystallization mother liquor in a chemical production workshop as an application scenario, the NTC thermistor and pH electrode were immersed together in the ammonium sulfate solution to be tested. Under standard constant temperature conditions, the temperature of the ammonium sulfate solution to be tested was controlled by a high-precision constant temperature bath. The resistance values ​​of the NTC thermistor at two characteristic temperature points, 25 degrees Celsius and 80 degrees Celsius, were measured and recorded as a set of characteristic point resistance values. The nominal resistance value measured at 25 degrees Celsius was 10 kiloohms, and the actual resistance value measured at 80 degrees Celsius was 0.8 kiloohms.

[0025] In some embodiments, the measurement is independently repeated three times under the same environmental conditions. Each measurement includes the complete acquisition of resistance values ​​at two characteristic temperature points. The arithmetic mean of the resistance values ​​at 25 degrees Celsius obtained from the three measurements, which is 10.00 kΩ, is taken as the first characteristic resistance. The arithmetic mean of the resistance values ​​at 80 degrees Celsius obtained from the three measurements, which is 0.80 kΩ, is taken as the second characteristic resistance. Optionally, based on the set of characteristic point resistance values, the improved temperature fitting algorithm is called to calculate the B-value parameter of the NTC thermistor. The first characteristic resistance of 10.00 kΩ, the second characteristic resistance of 0.80 kΩ, the first thermodynamic temperature of 298.15 Kelvin converted from 25 degrees Celsius, and the second thermodynamic temperature of 353.15 Kelvin converted from 80 degrees Celsius are substituted into the B-value calculation formula of the NTC thermistor to perform a single B-value fitting operation. The B-value calculation formula of the NTC thermistor is as follows: , Where: B represents the B-value parameter of the NTC thermistor, T1 represents the first thermodynamic temperature of 298.15 Kelvin, T2 represents the second thermodynamic temperature of 353.15 Kelvin, R1 represents the first characteristic resistance of 10.00 kΩ, R2 represents the second characteristic resistance of 0.80 kΩ, and ln represents the natural logarithm operation. The preliminary B-value is calculated to be 3550 Kelvin.

[0026] It is understandable that by replacing the ammonium sulfate solution sample and repeating the isothermal measurement process, performing the single B-value fitting operation five times, five preliminary B-values ​​are obtained: 3548 Kelvin, 3552 Kelvin, 3551 Kelvin, 3549 Kelvin, and 3550 Kelvin. The arithmetic mean of all preliminary B-values ​​is calculated to be 3550 Kelvin, and this arithmetic mean is determined as the final B-value parameter used to construct the resistance-temperature relationship.

[0027] In the specific implementation, using the calculated final B-value parameter of 3550 Kelvin, a complete resistance-temperature correspondence data table is constructed. The starting temperature is set to 25 degrees Celsius, the ending temperature to 80 degrees Celsius, and the temperature step value to 1 degree Celsius. 56 temperature gradient points are generated within the range of 25 degrees Celsius to 80 degrees Celsius, namely 25 degrees Celsius, 26 degrees Celsius, 27 degrees Celsius, and up to 80 degrees Celsius. Each temperature gradient point is converted into its corresponding thermodynamic temperature. The first characteristic resistance of 10.00 kΩ, the final B-value parameter of 3550 Kelvin, and the thermodynamic temperature corresponding to each temperature gradient point are substituted into the resistance calculation formula of the NTC thermistor to calculate the theoretical resistance value at each temperature gradient point. The resistance calculation formula of the NTC thermistor is that the resistance value is equal to the first characteristic resistance multiplied by an exponential function with the natural constant e as the base. The exponent of the exponential function is the difference between the final B-value parameter multiplied by the reciprocal of the first thermodynamic temperature and the reciprocal of the current thermodynamic temperature.

[0028] In some embodiments, a mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table. The theoretical resistance value corresponding to 25 degrees Celsius is 10.00 kΩ, the theoretical resistance value corresponding to 26 degrees Celsius is 9.52 kΩ, the theoretical resistance value corresponding to 27 degrees Celsius is 9.06 kΩ, and so on up to the theoretical resistance value corresponding to 80 degrees Celsius is 0.80 kΩ.

[0029] Optionally, by consulting the resistance-temperature correspondence data table, the measured real-time resistance signal is mapped to the corresponding actual thermodynamic temperature of the solution. When the real-time resistance value of the NTC thermistor measured during online monitoring is 5.60 kΩ, the resistance-temperature correspondence data table is consulted to find the temperature gradient point corresponding to the theoretical resistance value closest to this real-time resistance value, which is 40 degrees Celsius. Therefore, the actual thermodynamic temperature of the solution is determined to be 313.15 Kelvin. It can be understood that after constructing the resistance-temperature correspondence data table, the measured real-time resistance signal is used as the query key, and a linear interpolation method is used to interpolate the resistance values ​​between two adjacent temperature gradient points in the data table, further improving the mapping accuracy of the actual thermodynamic temperature.

[0030] In one embodiment of the present invention, the original measured value of the non-standard state electrode potential signal is read. This original measured value is generated by immersing the pH electrode in the ammonium sulfate solution to be tested and is acquired by a voltage detection circuit with high input impedance. Based on the theoretical relationship between temperature and electrode potential in the Nernst equation, the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the current solution is calculated. The standard temperature condition is set to 25 degrees Celsius and converted into a standard thermodynamic temperature.

[0031] Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the standard thermodynamic temperature, denoted as the first theoretical slope. This theoretical slope is equal to the product of the ideal gas constant and the standard thermodynamic temperature, divided by the Faraday constant, and then multiplied by the reciprocal of the number of electrons transferred in the electrode reaction. Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the actual thermodynamic temperature of the current solution, denoted as the second theoretical slope. This second theoretical slope is equal to the product of the ideal gas constant and the current actual thermodynamic temperature, divided by the Faraday constant, and then multiplied by the reciprocal of the number of electrons transferred in the electrode reaction. The reciprocal of the number of electrons is used to calculate the difference between the second theoretical slope and the first theoretical slope. This difference is taken as the change in the theoretical slope of the electrode potential caused by temperature change. Based on the calculated change in the theoretical slope of the electrode potential, a temperature compensation coefficient is generated. This temperature compensation coefficient is equal to the ratio of the first theoretical slope to the second theoretical slope. The temperature compensation coefficient is applied to the original measured value of the non-standard state electrode potential signal. The compensated electrode potential value is obtained through linear correction. That is, the compensated electrode potential value is equal to the original measured value multiplied by the temperature compensation coefficient.

[0032] In a specific implementation, taking the online monitoring of the pH value of a solution in the ammonium sulfate evaporation and crystallization process of a fertilizer plant as an application scenario, the pH electrode and temperature sensor are immersed together in the ammonium sulfate solution to be tested, and the original measured value of the non-standard state electrode potential signal is read. The original measured value of the non-standard state electrode potential signal is generated by the pH electrode being immersed in the ammonium sulfate solution to be tested and is acquired by a voltage detection circuit with high input impedance. At a certain monitoring moment, the original measured value of the non-standard state electrode potential signal is -150 mV. At the same time, the actual thermodynamic temperature of the solution is measured to be 313.15 Kelvin by the method described in the above embodiment.

[0033] In some embodiments, based on the theoretical relationship between temperature and electrode potential in the Nernst equation, the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the current solution is calculated. The standard temperature condition is set to 25 degrees Celsius and converted to a standard thermodynamic temperature of 298.15 Kelvin. The theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the standard thermodynamic temperature of 298.15 Kelvin is calculated and denoted as the first theoretical slope. The first theoretical slope is equal to the product of the ideal gas constant and the standard thermodynamic temperature, divided by the Faraday constant, and then multiplied by the reciprocal of the number of electrons transferred in the electrode reaction. The ideal gas constant is taken as 8.314 joules per mole per Kelvin, the Faraday constant is taken as 96485 coulombs per mole, and the number of electrons transferred in the electrode reaction is taken as... The first theoretical slope is calculated to be 0.02569 volts, or 25.69 millivolts. The second theoretical slope is calculated as the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the actual thermodynamic temperature of the solution (313.15 Kelvin). The second theoretical slope is equal to the product of the ideal gas constant and the actual thermodynamic temperature of the solution (313.15 Kelvin), divided by the Faraday constant, and then multiplied by the reciprocal of the number of electrons transferred in the electrode reaction. The calculated second theoretical slope is 0.02698 volts, or 26.98 millivolts. The difference between the second and first theoretical slopes is calculated and taken as the change in the theoretical slope of the electrode potential due to temperature change. This change is 26.98 millivolts minus 25.69 millivolts, which equals 1.29 millivolts.

[0034] Optionally, a temperature compensation coefficient is generated based on the calculated change in the theoretical slope of the electrode potential. The temperature compensation coefficient is equal to the ratio of the first theoretical slope to the second theoretical slope, i.e., 25.69 mV divided by 26.98 mV equals 0.952. The temperature compensation coefficient 0.952 is applied to the original measured value of the non-standard state electrode potential signal, -150 mV, and the compensated electrode potential value is obtained through linear correction. The compensated electrode potential value is equal to the original measured value of the non-standard state electrode potential signal multiplied by the temperature compensation coefficient, i.e., -150 mV multiplied by 0.952 equals -142.8 mV.

[0035] In specific implementation, the process of calculating the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the current solution, based on the theoretical relationship between temperature and electrode potential in the Nernst equation, uses the following formulas to calculate the first theoretical slope and the second theoretical slope: , in: This represents the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation. The ideal gas constant is 8.314 joules per mole per Kelvin. Represents thermodynamic temperature. This indicates the number of electrons transferred in the electrode reaction, in the measurement of hydrogen ion concentration. The value is 1. This represents the Faraday constant of 96,485 coulombs per mole.

[0036] In some embodiments, the standard thermodynamic temperature of 298.15 Kelvin is substituted into the formula to obtain the first theoretical slope S1, and the actual thermodynamic temperature of the solution of 313.15 Kelvin is substituted into the formula to obtain the second theoretical slope S2. The difference between S2 and S1 is calculated to obtain the change in the theoretical slope of the electrode potential. It can be understood that when the actual thermodynamic temperature of the solution is higher than the standard thermodynamic temperature, the second theoretical slope is greater than the first theoretical slope, the temperature compensation coefficient is less than 1, and the absolute value of the compensated electrode potential is less than the absolute value of the original measured value of the non-standard state electrode potential signal. Optionally, after completing the temperature compensation process, the compensated electrode potential value of -142.8 mV and the actual thermodynamic temperature of the solution of 313.15 Kelvin are output together to the subsequent pH calculation unit for substitution into the simplified expression of the Nernst equation to resolve the hydrogen ion concentration.

[0037] It is understood that when the actual thermodynamic temperature of the solution is lower than the standard thermodynamic temperature, the second theoretical slope is less than the first theoretical slope, the temperature compensation coefficient is greater than 1, and the absolute value of the compensated electrode potential is greater than the absolute value of the original measured value of the non-standard state electrode potential signal.

[0038] In one embodiment of the present invention, see [reference] Figure 3 The standard electrode potential, ideal gas constant, Faraday constant, and number of electrons transferred in the electrode reaction are obtained. These parameters are pre-stored in the parameter configuration unit of the measurement system. The standard electrode potential is the reference electrode potential value measured under standard hydrogen electrode conditions. The ideal gas constant is taken as 8.314 joules per mole per Kelvin, the Faraday constant is taken as 96485 coulombs per mole, and the number of electrons transferred in the electrode reaction is taken as 1 in the hydrogen ion concentration measurement. The compensated electrode potential value, the actual thermodynamic temperature of the solution, and the standard electrode potential, ideal gas constant, Faraday constant, and number of electrons transferred in the electrode reaction are substituted into the simplified expression of the Nernst equation for hydrogen ions.

[0039] The simplified expression is that the compensated electrode potential is equal to the standard electrode potential minus the product of the ideal gas constant and the actual thermodynamic temperature of the solution, divided by the product of the Faraday constant and the number of electrons transferred in the electrode reaction, and then multiplied by the natural logarithm of the hydrogen ion concentration. Algebraically transforming the expression after substitution, we separate the hydrogen ion concentration as an unknown from one side of the equation, resulting in a form where the logarithmic term containing the hydrogen ion concentration is located separately on one side. Starting from the simplified expression of the Nernst equation after substituting the standard electrode potential, ideal gas constant, Faraday constant, number of electrons transferred in the electrode reaction, compensated electrode potential, and actual thermodynamic temperature of the solution, we can further refine the equation on both sides. An exponential operation with the natural constant e as the base is performed. After the exponential operation is performed, the logarithmic term containing the hydrogen ion concentration is eliminated, resulting in an exponential equation with the hydrogen ion concentration as the unknown. The value of the exponential expression on the right side of the exponential equation is calculated, which consists of the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction. The reciprocal of the value of the exponential expression is taken to obtain the specific value of the hydrogen ion concentration in the ammonium sulfate solution. Based on the hydrogen ion concentration, the final pH value of the ammonium sulfate solution to be tested is calculated by a negative logarithmic operation with the base 10.

[0040] In a specific implementation, the application scenario is online detection of the pH value of the crystallizer outlet solution in an ammonium sulfate production workshop. After completing the temperature compensation process described in the above embodiment, the compensated electrode potential value is obtained as -142.8 mV. Simultaneously, the actual thermodynamic temperature of the solution is obtained as 313.15 Kelvin using the method described in the above embodiment. The standard electrode potential, ideal gas constant, Faraday constant, and the number of electrons transferred in the electrode reaction are obtained. The standard electrode potential is the reference electrode potential value measured under standard hydrogen electrode conditions. The standard electrode potential of the silver-silver chloride reference electrode used in this scenario is 0.197 volts. Assuming the ideal gas constant is 8.314 joules per mole per Kelvin, the Faraday constant is 96485 coulombs per mole, and the number of electrons transferred in the electrode reaction is 1, the compensated electrode potential of -142.8 mV (i.e., -0.1428 V), the actual thermodynamic temperature of the solution of 313.15 Kelvin, the standard electrode potential of 0.197 V, the ideal gas constant of 8.314 joules per mole per Kelvin, the Faraday constant of 96485 coulombs per mole, and the number of electrons transferred in the electrode reaction of 1 are substituted into the simplified expression of the Nernst equation for hydrogen ions. The simplified expression of the Nernst equation for hydrogen ions is as follows: , Where: E represents the compensated electrode potential value of -0.1428 volts, E0 represents the standard electrode potential of 0.197 volts, R represents the ideal gas constant of 8.314 joules per mole per Kelvin, T represents the actual thermodynamic temperature of the solution of 313.15 Kelvin, n represents the number of electrons transferred in the electrode reaction (1), F represents the Faraday constant of 96485 coulombs per mole, [H+] represents the hydrogen ion concentration in the ammonium sulfate solution, and ln represents the natural logarithm.

[0041] In some embodiments, the expression after substitution is algebraically transformed, separating the hydrogen ion concentration as an unknown from one side of the equation, resulting in a form where the logarithmic term containing the hydrogen ion concentration is located alone on one side of the equation. That is, the compensated electrode potential value minus the product of the standard electrode potential (equal to a negative ideal gas constant) and the actual thermodynamic temperature of the solution, divided by the product of the Faraday constant and the number of electrons transferred in the electrode reaction, and then multiplied by the natural logarithm of the hydrogen ion concentration, yields the natural logarithm of the hydrogen ion concentration equal to the difference between the standard electrode potential and the compensated electrode potential value, multiplied by the product of the Faraday constant and the number of electrons transferred in the electrode reaction, and then divided by the product of the ideal gas constant and the actual thermodynamic temperature of the solution. Substituting this value into the equation... Starting from the simplified expression of the Nernst equation, which takes the standard electrode potential, ideal gas constant, Faraday constant, number of electrons transferred in the electrode reaction, compensated electrode potential, and actual thermodynamic temperature of the solution, an exponential operation with the natural constant e is performed on both sides of the equation. After performing the exponential operation, the logarithmic term containing the hydrogen ion concentration is eliminated, resulting in an exponential equation with the hydrogen ion concentration as the unknown. That is, the hydrogen ion concentration is equal to an exponential function with the natural constant e as the base. The exponent of the exponential function is the product of the difference between the standard electrode potential and the compensated electrode potential, multiplied by the Faraday constant and the number of electrons transferred in the electrode reaction, and then divided by the product of the ideal gas constant and the actual thermodynamic temperature of the solution.

[0042] Optionally, the value of the exponential expression on the right side of the exponential form equation is calculated, which consists of the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction. The difference between the standard electrode potential and the compensated electrode potential is 0.197 volts minus -0.1428 volts, which equals 0.3398 volts. The product of the Faraday constant of 96485 coulombs per mole and the number of electrons transferred in the electrode reaction is 1, which is 96485 coulombs per mole, with a numerator of 0. 3398 volts multiplied by 96485 coulombs per mole equals 32787 joules per mole. The denominator is the ideal gas constant 8.314 joules per mole per Kelvin. Multiplying this by the actual thermodynamic temperature of the solution 313.15 Kelvin equals 2604 joules per mole. The exponent is 32787 divided by 2604, which equals 12.59. The value of 12.59 raised to the power of the natural constant e is 292000. Taking the reciprocal of this exponential expression, 292000, yields a hydrogen ion concentration of 3.42 × 10⁻⁶ joules per mole in the ammonium sulfate solution. -6 Moles per liter.

[0043] In specific implementation, based on the stated hydrogen ion concentration of 3.42 × 10⁻⁶... -6 The final pH value of the ammonium sulfate solution to be tested is calculated using a negative logarithm calculation to base 10, where pH equals the negative logarithm of the hydrogen ion concentration to base 10, i.e., pH = -lg(3.42 × 10⁻⁶). -6 The final pH value of the ammonium sulfate solution to be tested is 5.47. It can be understood that the value of the exponential expression changes exponentially with the change in the compensated electrode potential. When the compensated electrode potential increases, the difference between the standard electrode potential and the compensated electrode potential decreases, the exponential portion decreases, the value of the exponential expression decreases, the hydrogen ion concentration decreases, and the pH value increases.

[0044] In some embodiments, different compensated electrode potential values ​​and their corresponding actual thermodynamic temperatures of the solution are substituted into the above calculation process to obtain the relationship between hydrogen ion concentration and pH value of ammonium sulfate solution under different operating conditions, as shown in Table 1.

[0045] Table 1: Relationship between hydrogen ion concentration and pH value in ammonium sulfate solution

[0046] Optionally, when the difference between the compensated electrode potential and the standard electrode potential is positive, the exponent is positive, the value of the exponential expression is greater than 1, the hydrogen ion concentration is less than 1 mole per liter, and the pH value is positive. It can be understood that as the actual thermodynamic temperature of the solution increases, the denominator increases, the exponent decreases, the value of the exponential expression decreases, the hydrogen ion concentration decreases, and the pH value increases, exhibiting a trend of increasing pH with increasing temperature.

[0047] In one embodiment of the present invention, the nominal resistance value measured at 25 degrees Celsius is read from the set of characteristic point resistance values ​​and recorded as the first characteristic resistance. The actual resistance value measured at 80 degrees Celsius is read and recorded as the second characteristic resistance. 25 degrees Celsius and 80 degrees Celsius are converted to the corresponding first thermodynamic temperature of 298.15 Kelvin and the second thermodynamic temperature of 353.15 Kelvin, respectively. The first characteristic resistance, the second characteristic resistance, the first thermodynamic temperature, and the second thermodynamic temperature are substituted into the B-value calculation formula of the NTC thermistor. The calculation formula is that the B-value is equal to the product of the first thermodynamic temperature and the second thermodynamic temperature, divided by the difference between the second thermodynamic temperature and the first thermodynamic temperature, and then multiplied by the natural logarithm of the ratio of the second characteristic resistance to the first characteristic resistance. A single B-value fitting operation is performed to obtain a preliminary B-value. The ammonium sulfate solution sample is replaced and the isothermal measurement process is repeated. The single B-value fitting operation is performed multiple times to obtain multiple preliminary B-values. The arithmetic mean of all preliminary B-values ​​is calculated. The arithmetic mean of the values ​​is used as the final B-value parameter for constructing the resistance-temperature relationship. The starting temperature is set to 25 degrees Celsius, the ending temperature to 80 degrees Celsius, and the temperature step value to 0.5 degrees Celsius. A series of temperature gradient points are generated within the range of 25 degrees Celsius to 80 degrees Celsius. Each temperature gradient point is converted into its corresponding thermodynamic temperature. The first characteristic resistance, the final B-value parameter, and the thermodynamic temperature corresponding to each temperature gradient point are substituted into the resistance calculation formula of the NTC thermistor. This formula states that the theoretical resistance at the current temperature is equal to the first characteristic resistance multiplied by an exponential function with base e. The exponent of the exponential function is the difference between the final B-value parameter multiplied by the reciprocal of the first thermodynamic temperature and the reciprocal of the current thermodynamic temperature. The theoretical resistance value at each temperature gradient point is calculated. A mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table.

[0048] In a specific implementation, taking the calibration process of the NTC thermistor in the temperature detection module of a certain ammonium sulfate solution preparation process as an application scenario, the nominal resistance value of 10.00 kΩ measured at 25 degrees Celsius is read from the characteristic point resistance value set and recorded as the first characteristic resistance. The actual resistance value of 0.80 kΩ measured at 80 degrees Celsius is read and recorded as the second characteristic resistance. 25 degrees Celsius and 80 degrees Celsius are converted to the corresponding first thermodynamic temperature of 298.15 Kelvin and the second thermodynamic temperature of 353.15 Kelvin, respectively. The first characteristic resistance of 10.00 kΩ, the second characteristic resistance of 0.80 kΩ, the first thermodynamic temperature of 298.15 Kelvin, and the second thermodynamic temperature of 353.15 Kelvin are substituted into the formula for calculating the B value of the NTC thermistor. The formula for calculating the B value of the NTC thermistor is as follows: , in: The B-value parameter represents the NTC thermistor. The first thermodynamic temperature is 298.15 Kelvin. The second thermodynamic temperature is 353.15 Kelvin. This indicates that the first characteristic resistance is 10.00 kiloohms. The second characteristic resistance is 0.80 kiloohms. This represents the natural logarithm operation. A single B-value fitting operation is performed, yielding an initial B-value of 3550 Kelvin.

[0049] In some embodiments, the ammonium sulfate solution sample is replaced and the isothermal measurement process is repeated, performing the single B-value fitting operation five times to obtain five preliminary B-values ​​of 3548 Kelvin, 3552 Kelvin, 3551 Kelvin, 3549 Kelvin, and 3550 Kelvin. The arithmetic mean of all preliminary B-values, 3550 Kelvin, is calculated, and this arithmetic mean is determined as the final B-value parameter used to construct the resistance-temperature relationship. This final B-value parameter is denoted as... Kelvin.

[0050] Optionally, using the calculated final B-value parameter of 3550 Kelvin, a complete resistance-temperature correspondence data table is constructed. The starting temperature is set to 25 degrees Celsius, the ending temperature to 80 degrees Celsius, and the temperature step value to be 0.5 degrees Celsius. 111 temperature gradient points are generated within the range of 25 degrees Celsius to 80 degrees Celsius, successively at 25.0 degrees Celsius, 25.5 degrees Celsius, 26.0 degrees Celsius, and up to 80.0 degrees Celsius. Each temperature gradient point is converted to its corresponding thermodynamic temperature. The first characteristic resistance of 10.00 kΩ, the final B-value parameter of 3550 Kelvin, and the thermodynamic temperature corresponding to each temperature gradient point are substituted into the resistance calculation formula for the NTC thermistor to calculate the theoretical resistance value at each temperature gradient point. The resistance calculation formula for the NTC thermistor is as follows: ,in This represents the theoretical resistance value at the current thermodynamic temperature T. This indicates that the first characteristic resistance is 10.00 kiloohms. This indicates that the final value of parameter B is 3550 Kelvin. The first thermodynamic temperature is 298.15 Kelvin. This represents an exponential function with the natural constant e as the base.

[0051] In specific implementation, a mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table. For the mapping relationship of some temperature gradient points, please refer to Table 2.

[0052] Table 2: Resistance-Temperature Correlation Data Table

[0053] It is understandable that when a higher temperature resolution resistance-temperature correspondence is required, the temperature step value is reduced from 0.5 degrees Celsius to 0.1 degrees Celsius, generating 551 temperature gradient points within the range of 25 degrees Celsius to 80 degrees Celsius. The theoretical resistance value at each temperature gradient point is calculated to form a more accurate resistance-temperature correspondence data table. In some embodiments, the measurement of the first characteristic resistor and the second characteristic resistor uses a 4.5-digit precision digital multimeter, with a resistance reading resolution of 0.001 kiloohms, to ensure the accuracy of the B-value parameter calculation.

[0054] Optionally, during the calculation of the arithmetic mean of the final B-value parameter, the number of preliminary B-values ​​involved in the averaging process can be adjusted according to actual accuracy requirements. When the range of the preliminary B-values ​​exceeds 5 Kelvin, the number of repeated measurements is increased to 8 before calculating the arithmetic mean. It can be understood that the theoretical resistance value sequence generated at a temperature step of 0.5 degrees Celsius covers the complete operating range from 25 degrees Celsius to 80 degrees Celsius. The rate of change of resistance between adjacent temperature gradient points is less in the high-temperature region than in the low-temperature region, reflecting the negative temperature coefficient characteristic of the NTC thermistor.

[0055] In one embodiment of the present invention, after constructing the resistance-temperature correspondence data table, the ammonium sulfate solution is sequentially adjusted to each temperature gradient point recorded in the data table using a constant temperature device. At each temperature gradient point, after the solution temperature stabilizes, the actual resistance value of the NTC thermistor is measured using a multimeter. The measured actual resistance value is compared with the theoretical resistance value recorded in the data table, and the absolute error and relative error rate are calculated. The absolute error is equal to the absolute value of the actual resistance value minus the absolute value of the theoretical resistance value. The relative error rate is equal to the absolute error divided by the theoretical resistance value and then multiplied by 100%. If the relative error rate at any temperature gradient point exceeds 2%, the calculation of the B-value parameter and the construction of the data table are re-executed. The resistance values ​​at the two characteristic temperature points are re-measured, the final B-value parameter is recalculated, and the resistance-temperature correspondence data table is regenerated until the relative error rate at all temperature gradient points meets the preset accuracy requirement. The preset accuracy requirement is that the relative error rate at all temperature gradient points does not exceed 2%.

[0056] In practical implementation, the on-site calibration and verification of the temperature detection module before its commissioning in a certain ammonium sulfate evaporation and crystallization process is taken as the application scenario. After constructing the resistance-temperature correspondence data table, the ammonium sulfate solution is sequentially adjusted to the temperature gradient points recorded in the data table using a constant temperature device. The constant temperature device is a precision constant temperature water bath with a temperature control accuracy of ±0.05 degrees Celsius. The temperature gradient points recorded in the data table include four verification points: 25.0 degrees Celsius, 40.0 degrees Celsius, 60.0 degrees Celsius, and 80.0 degrees Celsius. At each temperature gradient point, after the temperature of the ammonium sulfate solution stabilizes, the actual resistance value of the NTC thermistor is measured using a 4.5-digit digital multimeter. The measured actual resistance value is compared with the theoretical resistance value recorded in the data table, and the absolute error and relative error rate are calculated. The formula for calculating the relative error rate is: , in: This represents the relative error rate. This represents the actual resistance value of the NTC thermistor as measured by a digital multimeter. This represents the theoretical resistance value recorded in the data table at the corresponding temperature gradient point.

[0057] In some embodiments, at a temperature gradient of 25.0 degrees Celsius, after the ammonium sulfate solution temperature stabilized, the actual resistance value measured was 10.03 kΩ, while the theoretical resistance value in the data table was 10.00 kΩ, with an absolute error of 0.03 kΩ and a relative error rate of 0.30%; at a temperature gradient of 40.0 degrees Celsius, the actual resistance value measured was 5.10 kΩ, the theoretical resistance value was 5.04 kΩ, the absolute error was 0.06 kΩ, and the relative error rate was 1.19%; at a temperature gradient of 60.0 degrees Celsius, the actual resistance value measured was 2.18 kΩ, the theoretical resistance value was 2.14 kΩ, the absolute error was 0.04 kΩ, and the relative error rate was 1.87%; at a temperature gradient of 80.0 degrees Celsius, the actual resistance value measured was 0.99 kΩ, the theoretical resistance value was 1.00 kΩ, the absolute error was 0.01 kΩ, and the relative error rate was 1.00%.

[0058] Optionally, a preset threshold is set to 2.0%. It is determined whether the relative error rate at all temperature gradient points exceeds the preset threshold. The relative error rates of the above four verification points are 0.30%, 1.19%, 1.87%, and 1.00%, respectively, all of which are less than 2.0%, meeting the preset accuracy requirements. The resistance-temperature correspondence data table passes the accuracy verification and can be directly used for subsequent temperature measurements.

[0059] It is understood that if the relative error rate at any temperature gradient point exceeds the preset threshold of 2.0%, the calculation of the B-value parameter and the construction of the data table are re-executed. The resistance values ​​at the two characteristic temperature points are re-measured, the final B-value parameter is recalculated, and the resistance-temperature correspondence data table is regenerated until the relative error rate at all temperature gradient points meets the preset accuracy requirements. In specific implementation, when the actual resistance value measured at the 60.0°C temperature gradient point is 2.30 kΩ, the theoretical resistance value is 2.14 kΩ, the absolute error is 0.16 kΩ, and the relative error rate is 7.48%, exceeding the preset threshold of 2.0%, the current data table is stopped. The resistance values ​​of the NTC thermistor at the two characteristic temperature points of 25°C and 80°C are re-measured under standard isothermal conditions and recorded as a new set of characteristic point resistance values. The improved temperature fitting algorithm is called again to calculate the B-value parameter of the NTC thermistor, the resistance-temperature correspondence data table is reconstructed, and the accuracy verification process is executed again on the newly constructed data table.

[0060] In some embodiments, the number of temperature gradient points selected during the accuracy verification process is five, covering the two ends and the middle area of ​​the temperature range in the data table, namely 25.0 degrees Celsius, 38.0 degrees Celsius, 52.0 degrees Celsius, 66.0 degrees Celsius, and 80.0 degrees Celsius. At each temperature gradient point, the actual resistance value is measured three times, and the arithmetic mean is compared with the theoretical resistance value to calculate the absolute error and relative error rate. Optionally, the preset threshold is set to 1.5% according to the measurement accuracy requirements. When the temperature measurement error required for calculating the pH of the ammonium sulfate solution is less than 0.2 degrees Celsius, the preset threshold is adjusted to 1.0% to more strictly control the accuracy of the resistance-temperature correspondence data table.

[0061] It is understood that after the accuracy verification is completed and passed, the resistance-temperature correspondence data table is stored in the storage unit of the temperature detection module, which is used to map the real-time resistance signal measured in the subsequent online monitoring process to the actual thermodynamic temperature of the corresponding ammonium sulfate solution.

[0062] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology, characterized in that, The method includes: Acquire the non-standard state electrode potential signal of the ammonium sulfate solution to be tested and the real-time resistance signal of the NTC thermistor; An improved temperature fitting algorithm is applied to the real-time resistance signal of the NTC thermistor to calculate the actual thermodynamic temperature of the solution. The improved temperature fitting algorithm is based on the nonlinear relationship between the resistance value of the feature point and the thermodynamic temperature, and reduces the temperature measurement error by optimizing the fitting process. Based on the actual thermodynamic temperature of the solution, temperature compensation processing is performed on the non-standard state electrode potential signal to correct the influence of thermodynamic temperature change on the electrode potential measurement value, and the compensated electrode potential value is obtained. Substituting the compensated electrode potential value and the actual thermodynamic temperature of the solution into the simplified expression of the Nernst equation, the hydrogen ion concentration in the ammonium sulfate solution is obtained by inverse solution. The final pH value of the ammonium sulfate solution to be tested is calculated using negative logarithmic operations based on the hydrogen ion concentration.

2. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 1, characterized in that, An improved temperature fitting algorithm is applied to the real-time resistance signal of the NTC thermistor to calculate the actual thermodynamic temperature of the solution, including: Under standard constant temperature conditions, the resistance values ​​of the NTC thermistor were measured at two characteristic temperature points, 25 degrees Celsius and 80 degrees Celsius, and recorded as a set of characteristic point resistance values. Based on the set of resistance values ​​at the feature points, the improved temperature fitting algorithm is called to calculate the B-value parameter of the NTC thermistor. The improved temperature fitting algorithm optimizes the B-value fitting result by taking the average value of multiple measurements. Using the calculated B-value parameter, a complete resistance-temperature correspondence data table is constructed, which covers a temperature range of 25 degrees Celsius to 80 degrees Celsius. By querying the resistance-temperature correspondence data table, the measured real-time resistance signal is mapped to the corresponding actual thermodynamic temperature of the solution.

3. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 2, characterized in that, The method of taking the average value of multiple measurements is as follows: at least three independent measurements are repeated under the same environmental conditions, and each measurement includes the complete acquisition of resistance values ​​at two characteristic temperature points.

4. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 1, characterized in that, Based on the actual thermodynamic temperature of the solution, temperature compensation processing is performed on the non-standard state electrode potential signal to correct the influence of thermodynamic temperature changes on the electrode potential measurement, including: Read the original measured value of the non-standard state electrode potential signal; Based on the theoretical relationship between temperature and electrode potential in the Nernst equation, calculate the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the solution described above. A temperature compensation coefficient is generated based on the calculated change in the theoretical slope of the electrode potential. The temperature compensation coefficient is applied to the original measured value of the non-standard state electrode potential signal, and the compensated electrode potential value is obtained through linear correction.

5. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 1, characterized in that, Substituting the compensated electrode potential and the actual thermodynamic temperature of the solution into the simplified expression of the Nernst equation, the hydrogen ion concentration in the ammonium sulfate solution is obtained by inverse solution, including: Obtain the standard electrode potential, ideal gas constant, Faraday constant, and the number of electrons transferred in the electrode reaction; Substitute the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction into the simplified expression of the Nernst equation for hydrogen ions. By performing algebraic transformations on the expression after substitution, the hydrogen ion concentration is separated from one side of the equation as an unknown. The hydrogen ion concentration in the ammonium sulfate solution can be directly calculated by solving the algebraically transformed equation through exponential operations.

6. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 2, characterized in that, Based on the set of characteristic point resistance values, the improved temperature fitting algorithm is used to calculate the B-value parameter of the NTC thermistor, including: The nominal resistance value measured at 25 degrees Celsius is read from the set of characteristic point resistance values ​​and recorded as the first characteristic resistance. The actual resistance value measured at 80 degrees Celsius is read and recorded as the second characteristic resistance. Convert 25 degrees Celsius and 80 degrees Celsius to their corresponding first and second thermodynamic temperatures, respectively. Substitute the first characteristic resistance, the second characteristic resistance, the first thermodynamic temperature, and the second thermodynamic temperature into the B-value calculation formula for the NTC thermistor, and perform a single B-value fitting operation to obtain the preliminary B-value. By changing the ammonium sulfate solution sample or repeating the isothermal measurement process, the single B-value fitting calculation is performed multiple times to obtain multiple preliminary B-values. Calculate the arithmetic mean of all preliminary B values, and determine this arithmetic mean as the final B value parameter used to construct the resistance-temperature relationship.

7. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 6, characterized in that, The calculation of the B-value parameter is used to construct a complete resistance-temperature correspondence data table, including: Set the starting temperature, ending temperature, and temperature step value to generate a series of temperature gradient points in the range of 25 to 80 degrees Celsius. Convert each temperature gradient point to its corresponding thermodynamic temperature; Substitute the first characteristic resistor, the final B value parameter, and the thermodynamic temperature corresponding to each temperature gradient point into the resistance calculation formula of the NTC thermistor to calculate the theoretical resistance value at each temperature gradient point. A mapping relationship is established between each temperature gradient point, its corresponding thermodynamic temperature, and the calculated theoretical resistance value, and stored in tabular form to form the resistance-temperature correspondence data table.

8. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 4, characterized in that, The calculation of the change in the theoretical slope of the electrode potential under standard temperature conditions and the actual thermodynamic temperature conditions of the solution, based on the theoretical relationship between temperature and electrode potential in the Nernst equation, includes: The standard temperature condition is set to 25 degrees Celsius and converted to standard thermodynamic temperature. Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the stated standard thermodynamic temperature, and denote it as the first theoretical slope; Calculate the theoretical slope of the electrode potential relative to the hydrogen ion concentration in the Nernst equation at the actual thermodynamic temperature of the solution described above, and denote it as the second theoretical slope; Calculate the difference between the second theoretical slope and the first theoretical slope, and use this difference as the change in the theoretical slope of the electrode potential caused by temperature change.

9. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 5, characterized in that, By solving the algebraically transformed equation using exponential operations, the hydrogen ion concentration in the ammonium sulfate solution can be directly calculated, including: Starting from the simplified expression of the Nernst equation after substituting the standard electrode potential, ideal gas constant, Faraday constant, number of electrons transferred in the electrode reaction, compensated electrode potential value, and actual thermodynamic temperature of the solution, exponential operations with the natural constant e are performed on both sides of the equation simultaneously. After performing the exponential operation, the logarithmic term containing the hydrogen ion concentration is eliminated, resulting in an exponential equation with the hydrogen ion concentration as the unknown. Calculate the value of the exponential expression on the right side of the exponential form equation, which consists of the compensated electrode potential, the actual thermodynamic temperature of the solution, the standard electrode potential, the ideal gas constant, the Faraday constant, and the number of electrons transferred in the electrode reaction. Taking the reciprocal of the numerical value of the exponential expression yields the specific numerical value of the hydrogen ion concentration in the ammonium sulfate solution.

10. The method for calculating the pH of ammonium sulfate based on electrochemical principles and temperature compensation technology according to claim 7, characterized in that, After constructing the resistance-temperature correspondence data table, the method further includes verifying the accuracy of the data table: The ammonium sulfate solution was sequentially adjusted to the temperature gradient points recorded in the data table using a constant temperature device. At each temperature gradient point, after the solution temperature stabilizes, use a multimeter to measure the actual resistance value of the NTC thermistor. The measured actual resistance value is compared with the theoretical resistance value recorded in the data table, and the absolute error and relative error rate are calculated. If the relative error rate at any temperature gradient point exceeds the preset threshold, the calculation of the B-value parameter and the construction of the data table will be re-executed until the relative error rate at all temperature gradient points meets the preset accuracy requirements.

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