High-temperature low-pressure trace water vapor concentration testing algorithm

Abstract

The invention discloses a high-temperature low-pressure trace water vapor concentration test algorithm, belongs to the technical field of detection algorithms of related sensors, and aims to solve the problem that a Karl Fischer method is unsuitable for real-time measurement due to long measurement time since a calibration reagent is used for reacting with water vapor in gas to be measured. In order to solve the problem that when gas to be measured contains substances with the same components as a calibration reagent, the measurement result deviates, the method comprises the following steps of: performing curve fitting by utilizing a voltage value acquired from an ADC (Analog to Digital Converter), and selecting 10 data points on each of two sides without an absorption peak so as to fit an unabsorbed signal curve; the system has excellent applicability, is not limited by environmental conditions, and can continuously monitor the water vapor concentration in real time in an environment where the temperature and the pressure change, and if the temperature and the pressure change, the system can quickly respond, adjust the concentration calculation and ensure the accuracy and the timeliness of data.

Description

Technical Field

[0001] This invention belongs to the field of sensor detection algorithm technology, specifically relating to a high-temperature, low-pressure trace water vapor concentration testing algorithm. Background Technology

[0002] Moisture is a critical factor that needs to be strictly controlled during the production of lithium-ion batteries. Excessive moisture can not only lead to the decomposition of lithium salts in the electrolyte and cause corrosion and damage to the positive and negative electrode materials and current collectors, but also reduce the battery's cycle performance and safety. However, less moisture in lithium batteries is not necessarily better. The solid electrolyte interface (SEI film) is a selectively permeable membrane that allows Li+ ions to pass through freely, while electrolyte molecules cannot. The composition of the electrolyte and trace additives have a significant impact on the SEI film formation potential, density, irreversible capacity loss, and internal resistance of the battery. Water, as a trace component in the electrolyte, has a certain influence on the formation of the SEI film and battery performance in lithium-ion batteries.

[0003] Currently, the main method for measuring water vapor in trace batteries in my country is the Karl Fischer technique: this involves reacting water vapor in the analyte gas with a Karl Fischer reagent of known titer. The Karl Fischer reagent is primarily composed of iodine, sulfur dioxide, pyridine, and methanol. The reagent is calibrated using a standard gas with a known water vapor concentration to obtain its water equivalent concentration, and then the process is repeated. This reagent is then used to react with water vapor in the analyte gas to determine the water concentration. The Karl Fischer method uses a calibrating reagent to react with water vapor in the analyte gas, resulting in a long measurement time, making it unsuitable for real-time measurements. Furthermore, if the analyte gas contains substances with the same components as the calibrating reagent, the measurement results will deviate. Additionally, the sublimation of iodine during the measurement process necessitates frequent reagent calibration, increasing the workload.

[0004] Therefore, a high-temperature, low-pressure trace water vapor concentration testing algorithm is needed. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature, low-pressure trace water vapor concentration testing algorithm to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-temperature, low-pressure trace water vapor concentration testing algorithm, comprising the following steps:

[0007] S1: We use the voltage values ​​collected from the ADC to perform curve fitting, and select 10 data points on each side of the area without absorption peaks to fit the unabsorbed signal curve.

[0008] S2: The relative absorption rate is obtained by dividing the original signal acquired by the ADC by the newly fitted curve and taking the logarithm (LN).

[0009] S3: Based on the obtained relative absorptivity and the pressure and temperature values ​​we set, and by looking up the corresponding absorption cross-sectional coefficient and absorbance in the HITRAN database;

[0010] S4: Calculate the gas concentration value based on Lambert-Beer's law and unit conversion.

[0011] The solution requires the following unit conversion when substituting the absorbance into the following ppm formula:

[0012]

[0013] C is the number density of molecules of the absorbed substance per unit volume: the unit is molecules / cm³. 3

[0014] in:

[0015]

[0016] In practical applications, ppm is often used to express the concentration of a gas;

[0017]

[0018] Finally converted to:

[0019]

[0020] Compared with existing technologies, the high-temperature, low-pressure trace water vapor concentration testing algorithm provided by this invention has at least the following beneficial effects:

[0021] (1) This invention uses theoretical calculation and processing analysis, advanced mathematical models and data correction technology to minimize measurement errors and obtain reliable water vapor concentration values.

[0022] (2) The present invention has excellent applicability and is not limited by environmental conditions. In environments where temperature and pressure change, it can continuously monitor water vapor concentration in real time. If temperature and pressure change, the system can respond quickly and adjust the concentration calculation to ensure the accuracy and timeliness of the data. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process of the present invention;

[0024] Figure 2This is a schematic diagram illustrating the parameter settings for the Spectraplot website according to the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, but not all embodiments. Based on the described 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.

[0027] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0028] Please see Figure 1-2 This invention provides an algorithm for testing trace water vapor concentration at high temperature and low pressure, comprising the following steps:

[0029] S1: We use the voltage values ​​collected from the ADC to perform curve fitting, and select 10 data points on each side of the area without absorption peaks to fit the unabsorbed signal curve.

[0030] S2: The relative absorption rate is obtained by dividing the original signal acquired by the ADC by the newly fitted curve and taking the logarithm (LN).

[0031] S3: Based on the obtained relative absorptivity and the pressure and temperature values ​​we set, and by looking up the corresponding absorption cross-sectional coefficient and absorbance in the HITRAN database;

[0032] S4: Calculate the gas concentration value based on Lambert-Beer's law and unit conversion.

[0033] When processing the voltage values ​​acquired by the ADC, a fitting method was adopted. First, the voltage values ​​were fitted using an appropriate mathematical model and algorithm to construct a fitting curve. This fitting curve can capture the trends and characteristics in the original data.

[0034] Next, the fitted curve is compared with the relevant data in the database. By dividing the fitted curve by the number of data points, a flattened graph can be obtained. This flattened graph can be used for data analysis and comparison to evaluate the consistency and accuracy between the fitted curve and the database.

[0035] This comparison process helps verify whether the fitted curve can accurately describe the original data and match the reference data in the database. Through this comparison, it can be determined whether the fitted curve can provide reliable concentration values ​​and is consistent with known database data. This fitting and comparison method can improve the accuracy and reliability of data analysis, thereby providing a reliable basis for subsequent concentration calculations and applications.

[0036] First, set the required parameters on the Spectraplot website, including temperature, pressure, gas absorption cell length, laser wavelength range, etc., and select a water vapor concentration value. The parameter settings are as follows: Figure 2 As shown.

[0037] Using 10,000 ppm at 1 atmosphere (25°C, 35°C, 50°C, 75°C, 90°C, and 105°C) as standard values, the corresponding water vapor concentration at 0.5 atmospheres was calculated. The absorbance at 25°C, 35°C, 50°C, 75°C, 90°C, and 105°C was obtained from the database and calculated using the formula, yielding the following results:

[0038] Substitute the absorbance into the following formula for ppm for calculation, where unit conversion is required:

[0039] C is the molecular number density of the absorbed substance per unit volume: the unit is molecules / cm3.

[0040]

[0041] in:

[0042]

[0043] In practical applications, ppm is often used to express the concentration of a gas;

[0044]

[0045] Finally converted to:

[0046]

[0047] The following results were obtained:

[0048] Where: T: temperature, in °C

[0049]

[0050]

[0051] A: Absorbance, unitless, can be measured experimentally.

[0052] P: Pressure, unit Pa

[0053] L: Optical path cell length, in cm

[0054] σ(λ): Section modulus, which is related to wavelength, pressure and temperature, and can be found in the Hitran database.

[0055] Finally, the result is calculated using the formula.

[0056] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The words “comprising” or “including” and similar terms used in this invention mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects. The words “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but may also include electrical connections, whether direct or indirect. “Up,” “down,” “left,” “right,” etc., are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature, low-pressure trace water vapor concentration testing algorithm, characterized in that, Includes the following steps: S1: We use the voltage values ​​collected from the ADC to perform curve fitting, and select 10 data points on each side of the area without absorption peaks to fit the unabsorbed signal curve. S2: The relative absorption rate is obtained by dividing the original signal acquired by the ADC by the newly fitted curve and taking the logarithm (LN). S3: Based on the obtained relative absorptivity and the pressure and temperature values ​​we set, and by looking up the corresponding absorption cross-sectional coefficient and absorbance in the HITRAN database; S4: Calculate the gas concentration value based on Lambert-Beer's law and unit conversion.

2. The high-temperature, low-pressure trace water vapor concentration testing algorithm according to claim 1, characterized in that: Substituting the absorbance into the following ppm formula for calculation, the required unit conversions are as follows: C is the number density of molecules of the absorbed substance per unit volume: the unit is molecules / cm³. 3 in: In practical applications, ppm is often used to express the concentration of a gas; Finally converted to:

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