An infrared oil detector driven by pulse signal

Abstract

The application provides an infrared oil measuring instrument driven by a pulse signal, and relates to the technical field of detection, which comprises generating a pulse width modulation signal, generating a constant peak current based on the pulse width modulation signal, and driving an infrared LED lamp with a preset characteristic absorption wave number to emit a pulse infrared light. After the pulse infrared light passes through a measuring tube containing a to-be-measured solution, the transmitted light is received and converted into an electric signal, the electric signal is processed to generate an absorbance value, and the oil concentration is calculated based on the absorbance value and a pre-designed calculation model. The application improves the intensity of the LED light source through pulse driving, combines multi-wavelength characteristic detection and constant current control, significantly improves the measurement accuracy and system stability, reduces the manufacturing cost, and is suitable for online or portable oil monitoring scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of detection, in particular to an infrared oil measuring instrument driven by pulse signals. BACKGROUND

[0002] At present, according to the international standard, the common method for measuring oil in water is infrared photometry. However, the infrared photometry requires an infrared light source with a specific wavelength. The existing infrared photometry instrument uses a continuous wavelength infrared spectrometer to achieve the required infrared wavelength of the infrared oil measuring instrument. In this way, the system complexity of the infrared oil measuring instrument is high, and the cost is also very high. If an infrared LED light source is used, the system complexity of the infrared oil measuring instrument can be greatly reduced, and the price of the infrared measuring instrument can be greatly reduced. However, the infrared LED lamp needs to be driven by a forward current. When the direct current is too large, the diode will heat up, which not only reduces the working efficiency, but also damages the device. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides an infrared oil measuring instrument driven by pulse signals, comprising:

[0004] A pulse width modulation signal is generated, and a constant peak current is generated based on the pulse width modulation signal. The constant peak current is used to drive an infrared LED lamp with a preset characteristic absorption wave number to emit pulse infrared light.

[0005] The pulse infrared light is guided to pass through a measuring tube containing a to-be-measured solution, the pulse infrared light transmitted by the to-be-measured solution is received, and the pulse infrared light is converted into a first electric signal corresponding to each preset characteristic absorption wave number.

[0006] Each first electric signal is processed to generate an absorbance value corresponding to each preset characteristic absorption wave number.

[0007] Based on the absorbance value and a pre-calibrated coefficient, the oil concentration in the to-be-measured solution is calculated according to a preset calculation model.

[0008] As an optional implementation, the present application further comprises:

[0009] A reference light path is provided.

[0010] At least one reference infrared LED lamp corresponding to the preset characteristic absorption wave number is driven by the constant peak current to emit reference pulse infrared light and guide it to pass through the reference light path.

[0011] The microcontroller synchronously controls the infrared LED lamps in the sample light path and the reference light path to emit pulse infrared light.

[0012] receiving the reference pulse infrared light transmitted through the reference light path and converting it into reference electrical signals corresponding to each of the preset characteristic absorption wavenumbers;

[0013] calculating, by the microcontroller, a differential signal in real time based on the first electrical signals and the reference electrical signals;

[0014] processing each of the first electrical signals based on the differential signal to generate absorbance values corresponding to each of the preset characteristic absorption wavenumbers.

[0015] As an optional implementation, it further comprises:

[0016] monitoring, by a sensor, a feedback signal reflecting the intensity of the transmitted light in the sample light path in real time;

[0017] running, by the microcontroller, a control algorithm based on the feedback signal to adaptively adjust at least one of the following:

[0018] adjusting, by an actuator, at least one optical path parameter of the sample light path;

[0019] adjusting at least one parameter of the pulse width modulation signal to control the intensity of the light source.

[0020] As an optional implementation, it further comprises performing calibration before calculating the oil concentration in the solution to be measured, the calibration comprising:

[0021] for a standard solution of known concentration, performing the following operations:

[0022] driving the infrared LED lamp with the constant peak current to emit the pulse infrared light;

[0023] guiding the pulse infrared light to pass through the measuring tube containing the standard solution;

[0024] receiving the pulse infrared light transmitted through the standard solution and converting it into corresponding standard solution electrical signals corresponding to each of the preset characteristic absorption wavenumbers;

[0025] processing each of the standard solution electrical signals to determine the absorbance values of the standard solution corresponding to each of the preset characteristic absorption wavenumbers;

[0026] based on the known concentration of the standard solution and its determined absorbance values, calculating the pre-calibration coefficient and the correction factor of the pre-calibration coefficient.

[0027] As an optional implementation, the preset characteristic absorption wavenumbers are 2930 , 2960 , and 3030 ; the preset calculation model is:

[0028]

[0029] wherein, represents the calculated oil concentration, , , are absorbance values measured at 2930 , 2960 and 3030 wavenumbers, respectively, X, Y, Z represent the pre-calibrated coefficients corresponding to the target chemical bond absorbance, F represents a correction factor of the pre-calibrated coefficient of the influence of aliphatic hydrocarbons on aromatic hydrocarbons, represents the volume of the extraction solution, represents the volume of the sample, and D represents the dilution multiple of the extraction solution, represents the concentration of the blank sample.

[0030] As an optional implementation, it further comprises:

[0031] monitoring the time variation of the absorbance values in real time;

[0032] when it is detected that at least one of the absorbance values has a rapid increase exceeding a preset threshold within a preset short time window, determining the relative variation pattern of the absorbance values at each corresponding wavenumber during the rapid increase;

[0033] comparing the relative variation pattern with the expected spectral absorption characteristic pattern of the oil concentration change based on a preset criterion:

[0034] in response to the relative variation pattern not conforming to the expected spectral absorption characteristic pattern, determining that a transient physical interference occurs;

[0035] in response to the relative variation pattern conforming to the expected spectral absorption characteristic pattern, determining that the oil concentration has a real change;

[0036] in response to determining that a transient physical interference occurs, performing a preset suppression or marking process on the oil concentration result calculated based on the absorbance values during the rapid increase.

[0037] As an optional implementation, the determination of the relative variation pattern of the absorbance values at each corresponding wavenumber during the rapid increase comprises:

[0038] performing Fourier transform on the first electrical signal of the corresponding wavenumber during the rapid increase to obtain a frequency spectrum including the pulse frequency of the pulsed infrared light and its harmonics;

[0039] determining an amplitude ratio and / or a relative phase relationship between a fundamental component of the pulse frequency and at least one harmonic component of the pulse frequency in the frequency spectrum;

[0040] comparing the determined amplitude ratio and / or relative phase relationship with a preset reference harmonic structure parameter to generate a comparison result;

[0041] determining whether the transient physical disturbance occurs based on the comparison result.

[0042] As an optional implementation, further comprising:

[0043] the microcontroller cooperatively adjusts the optical path parameter and the pulse width modulation signal parameter based on the feedback signal and the difference signal:

[0044] obtaining a current system state; wherein the current system state comprises at least one or a combination of the following: a current value of the feedback signal, a current value of the difference signal, a change rate of the feedback signal, a change rate of the difference signal, a result of determining whether the transient physical disturbance occurs, and a set value of the optical path parameter and the pulse width modulation signal parameter currently applied;

[0045] for a set of candidate cooperative adjustment amounts, based on the current system state, a preset state transition model is used to predict future state values of one or more measurement signal indicators after each candidate cooperative adjustment amount is applied;

[0046] wherein each of the candidate cooperative adjustment amounts comprises a combination of adjustments to the optical path parameter and the pulse width modulation signal parameter;

[0047] determining an optimization objective function according to the current system state to evaluate the future state values corresponding to each candidate cooperative adjustment amount; wherein the optimization objective function aims to maximize the accuracy of oil concentration calculation;

[0048] selecting the candidate cooperative adjustment amount that makes the optimization objective function optimal, and controlling the actuator and the pulse width modulation signal based on the selected candidate cooperative adjustment amount.

[0049] Compared with the prior art, the application drives the infrared LED lamp by pulse width modulation signal combined with constant peak current, can instantaneously improve the light intensity while maintaining the LED life and heat control, significantly improves the intensity of the transmitted light signal and the measurement signal-to-noise ratio, and solves the problem of insufficient light intensity of low-cost LED light source. Secondly, at least three specific wave numbers of infrared LED are used, which can accurately cover the characteristic absorption of different groups in oil substances, combined with absorbance processing and specific calculation model, improve the accuracy of oil concentration quantitative measurement, overcome the problem of poor component separation ability of traditional single-band detection. Thirdly, through the complete closed-loop process of pulse infrared light emission, transmission detection, signal processing and concentration calculation, the system structure is simplified, the manufacturing cost is reduced and the measurement process consistency is realized, which has good application stability and popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The implementation principle diagram of the multiple wavelengths of infrared light measuring the sample provided by the application;

[0051] Figure 2 The waveform diagram of the pulse driving frequency of the multiple infrared wavelengths provided by the application;

[0052] Figure 3 The circuit principle diagram of the strobe infrared LED driving circuit provided by the application;

[0053] Figure 4 The circuit principle diagram of the strobe infrared light signal receiving processing provided by the application;

[0054] Figure 5 The system flow chart of an infrared oil measurement method provided by the application;

[0055] Figure 6 The flow chart of an infrared oil measurement instrument driven by a pulse signal of the infrared LED lamp provided by the embodiment of the application. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the application will be described clearly and completely in the embodiments of the application combined with the drawings. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments of the application.

[0057] The research found that for the problem of infrared LED in the work, the infrared LED can be made to work in pulse state to avoid the problem caused by excessive current. In addition, pulse operation can also increase the gain and efficiency of infrared LED. In the pulse working state, the diode can withstand higher transient current and radiate more photons in a short time, thereby improving the output optical power and emission intensity. In this way, the problem that the infrared LED is difficult to produce strong infrared light due to insufficient light source intensity when it is always on can be avoided. In the pulse working state, the light intensity, energy and amplitude of the infrared LED output will change. These changes are related to factors such as pulse width, frequency and pulse duty cycle. Therefore, pulse operation can modulate and control the infrared LED, so that its output light meets the specific application requirements.

[0058] Referring to Figure 6 As shown in the flowchart of an infrared oil measuring instrument provided by the embodiment of the present application, the flowchart comprises steps S101-S104, wherein:

[0059] S101: generating a pulse width modulation signal, generating a constant peak current based on the pulse width modulation signal, and driving infrared LED lamps of preset characteristic absorption wavelengths with the constant peak current to emit pulsed infrared light;

[0060] S102: guiding the pulsed infrared light to pass through a measuring tube containing a to-be-measured solution, then receiving the pulsed infrared light transmitted through the to-be-measured solution, and converting the pulsed infrared light into first electric signals corresponding to each of the preset characteristic absorption wavelengths;

[0061] S103: processing each of the first electric signals to generate absorbance values corresponding to each of the preset characteristic absorption wavelengths;

[0062] S104: calculating the oil concentration in the to-be-measured solution according to a preset calculation model based on the absorbance values and a pre-calibrated coefficient.

[0063] For the above S101:

[0064] In a specific implementation, the core control unit of the system, for example, a microcontroller (MCU), is configured to generate a digitized pulse width modulation (PWM) signal. The parameters of the PWM signal, such as frequency and duty cycle, can be accurately controlled and adjusted by the MCU according to a preset program or real-time demand, thereby providing a basic control signal for subsequent generation of light pulses with specific characteristics.

[0065] For example, a pulse frequency in the range of hundreds of hertz to several thousand hertz and a duty cycle adjustable in a wide range can be selected. Then, the pulse width modulation signal generated by the MCU is sent to a specially designed constant current source circuit.

[0066] Referring to Figure 3 as shown, Figure 3 The circuit schematic of the stroboscopic infrared LED driving circuit provided in the present application; a peak constant current alternating power supply generated by a PWM signal output from the MCU pin is composed of resistor R80, PNP transistor Q12, resistor R89, adjustable voltage regulator diode D35, resistor R111, NPN transistor Q7, which controls the infrared LED lamp.

[0067] Among them, resistor R80 is used to receive the PWM signal from the MCU; PNP transistor Q12 and resistor R89 constitute the input control part; the core constant current control part can be composed of NPN transistor Q7, adjustable voltage regulator diode D35 (and resistor R111 (set reference current) and the like. The function of this constant current source circuit is to convert the input PWM signal representing the switching timing into a driving pulse with constant peak current.

[0068] For example, when the PWM signal is at an active level, the circuit is turned on, the driving current rises rapidly to the peak value set by D35 and R111 and the like, and remains relatively constant during this period; when the PWM signal is at an inactive level, the circuit is quickly turned off, and the driving current drops to zero or near zero.

[0069] The purpose of such design is to keep the peak current flowing through the LED stable, regardless of the slight changes in the supply voltage or the LED's own parameters (such as forward voltage), thereby ensuring good consistency in the intensity of each light pulse. Next, use this pulse driving signal with constant peak current to drive specific infrared light-emitting diodes (LEDs).

[0070] In specific implementation, three infrared LEDs can be selected, the center wavelengths of which correspond to the preset wave numbers characteristic of the absorption of oil substances.

[0071] Specifically, the preferred wave combination is , and , which correspond to the characteristic absorption peaks of methylene, methyl and aromatic ring C-H bonds in oil substances, respectively. The constant peak current pulse is applied to these three (or more, if other components need to be measured) specific infrared LEDs. The MCU can control the current pulse to be applied to different LEDs in turn, realizing time-sharing multiplexing measurement of multiple wavelengths; or if the system design allows multiple parallel driving, it can also be controlled as needed.

[0072] Under the constant peak current driving, each selected infrared LED will emit pulsed infrared light corresponding to its characteristic wave number during its effective pulse. For example, please refer toFigure 2 , Figure 2 Schematic diagram of the waveform of the pulse drive frequency of multiple infrared wavelengths provided in this application; for example, the pulse width may be in the microsecond range, and the peak current may be in the range of hundreds of milliamperes to several amperes. The specific parameters are set according to the characteristics of the LED and the required light intensity, and can be referenced but not limited to Figure 2 Example parameters shown.

[0073] For example, in Figure 2 In the figure, the upper waveform corresponds to the normal power working mode, with a pulse peak current of about 200 mA and a single cycle of 500 μs, of which the on and off periods each account for 250 μs, and the overall duty cycle is 50%, which can provide a stable medium luminous flux while ensuring the thermal safety of the device. The lower waveform in the figure corresponds to the enhanced power working mode, with a pulse peak current of about 2 A, a single pulse width of about 1 μs, an interval between adjacent pulses of about 500 μs, and a duty cycle of less than 0.2%. It uses short-term high-current pulses to instantly increase the radiant power within the allowable range of the device's thermal capacity to obtain high peak light intensity. The two waveforms can be applied alternately or independently to different central wave numbers ( 、 、 ) infrared LED to achieve a trade-off between measurement sensitivity and device lifetime.

[0074] Due to the use of pulsed drive and the application of higher peak current, these infrared LEDs can instantly emit stronger optical power than under DC drive, thereby meeting the signal strength requirements of subsequent optical measurements. At the same time, since the pulse duty cycle is usually low, the average power consumption and heat generation of the LED can be controlled within a safe range.

[0075] In this way, the output result of step S101 is to generate a series of pulsed infrared lights with stable peak intensity and specific timing at the preset characteristic wave number, which is ready for subsequent measurement through the sample.

[0076] Regarding S102 above:

[0077] In a specific implementation, the pulsed infrared light emitted from the infrared LED light source is precisely guided to and passes through a specially designed measuring tube. The structure of the measuring tube can be referred to Figure 1 , Figure 1 The schematic diagram of the principle of implementing the infrared light measurement of multiple wavelengths provided in this application is mainly used to accommodate the solution to be tested. The solution to be tested is usually a water sample containing the oil substance to be tested or its extract, such as a solution obtained by using tetrachloroethylene as an extractant. The measuring tube has a clear optical path length and is provided at both ends of the optical path with a selected infrared wave number (e.g. 、 and ) Optical window with good transmittance.

[0078] When pulsed infrared light travels through the solution being measured in the measuring tube, the oil present in the solution absorbs some of the infrared light's energy at its characteristic absorption wavenumber, with the degree of absorption following the Lambert-Beer law. Consequently, the intensity of the pulsed infrared light attenuates after passing through the solution, and this attenuation directly reflects the concentration of the oil component in the solution being measured.

[0079] One or more infrared light receivers (also known as infrared sensors) are strategically placed at the light-emitting end of the measuring tube to ensure that they can effectively receive the pulsed infrared light that has been transmitted through the solution to be measured and whose intensity has been attenuated. The sensor must be selected to ensure that its spectral response covers the infrared wavenumbers used and has a fast enough response speed to capture the pulse signal. Depending on the design, the system can use a single sensor with a light source for time-sharing drive, or Figure 1 As shown, multiple sensors are set up to perform parallel detection corresponding to different wavelengths.

[0080] The core function of the infrared light receiver is to convert the received pulsed optical signal into a corresponding electrical signal with varying amplitude in real time. This first electrical signal is also pulsed, with its amplitude or pulse integral proportional to the intensity of the transmitted light at the corresponding wavenumber. Therefore, for each wavenumber of pulsed infrared light, a corresponding first electrical signal pulse sequence is generated at the receiver output. This sequence forms the basis for subsequent signal processing and concentration calculation.

[0081] Regarding S103 above:

[0082] In step S102, the infrared light receiver converts the pulsed light signal after passing through the sample into a first electrical signal. After entering step S103, a series of processing is required for this first electrical signal, which is usually weak and has pulse characteristics, to extract stable and accurate absorbance information. Figure 4 As shown, Figure 4 The circuit schematic diagram of the stroboscopic infrared light signal receiving and processing provided by the present application is as follows: the first electrical signal is first input into a signal amplifying circuit. The amplifying circuit can be composed of a low-noise operational amplifier (such as Figure 4 It is composed of U7A in the figure) and precisely configured peripheral resistors and capacitors (such as R141, R155, C281, C250, etc.). Its function is to effectively amplify the weak first electrical signal to obtain a second electrical signal with a higher amplitude for subsequent processing.

[0083] Considering the noise that may be introduced by the pulse light source and the environment, the amplified second electrical signal needs to be filtered. In this embodiment, a two-stage low-pass filtering strategy can be adopted to obtain a good filtering effect. The second electrical signal is firstly filtered by an active low-pass filter. The active filter can be composed of an operational amplifier (such as Figure 4 The first filter is then passed through a passive RC low-pass filter (e.g., Figure 4 The second filter stage (comprised of R203 and C152) effectively suppresses noise and smoothes the original pulsed signal waveform into a near-DC third electrical signal with an amplitude approximately equal to the average light intensity during the pulse.

[0084] The resulting third electrical signal, whose voltage or current amplitude represents the average intensity of the transmitted light after passing through the sample at a specific wavenumber, needs to be digitized for processing by the MCU. This third electrical signal is fed into an analog-to-digital (A / D) conversion circuit. The A / D converter samples and quantizes the third electrical signal with sufficient sampling accuracy (e.g., 12 bits or higher) and an appropriate sampling rate, converting it into a series of digital values. These digital values ​​represent the intensity (I) of the transmitted light at the corresponding wavenumber. For time-multiplexed multi-wavelength measurements, the MCU associates the A / D conversion results with the corresponding wavenumber based on the wavelength of the currently driven LED. These digitized intensity signals are then transmitted to the MCU.

[0085] Finally, the MCU calculates the absorbance (A) based on the received digitized transmitted light intensity value (I). According to the Lambert-Beer law, absorbance is defined as the negative logarithm of the ratio of the incident light intensity to the transmitted light intensity (I). Therefore, the MCU needs to obtain the baseline light intensity or reference light intensity corresponding to each wave number. .this The value can be obtained by measuring a reference substance (for example, pure extraction solvent or blank sample without oil) before or periodically measuring the sample, and storing the corresponding digital intensity value. After that, the MCU performs the calculation: , or use other equivalent calculation methods (such as ), thereby obtaining the absorbance value at this wave number. 、 and For these three wave numbers, MCU will calculate the corresponding absorbance values 、 and These calculated absorbance values are the key input data necessary for the final oil concentration calculation in step S104.

[0086] For the above S104:

[0087] In a specific implementation, the MCU will use the real-time measured absorbance values, combined with the calibration parameters pre-stored in the internal memory, to calculate the final oil concentration in the solution to be measured according to the pre-set calculation model.

[0088] The pre-calibrated coefficients refer to the parameters obtained by performing an independent calibration program. This calibration program is usually performed when the instrument is first used or regularly maintained, by measuring standard solutions of known concentration containing different types of hydrocarbons (such as n-hexadecane, isooctane, benzene), and solving the system of equations to determine the coefficients X (corresponding to the group), Y (corresponding to the group), Z (corresponding to the aromatic ring C-H group), and the correction factor F for correcting the influence of aliphatic hydrocarbons on the measurement of aromatic hydrocarbons. These calibrated coefficients X, Y, Z, F are stored as an important basis for subsequent measurement of unknown samples.

[0089] The pre-set calculation model, in this embodiment, specifically uses the following mathematical formula to calculate the oil concentration :

[0090]

[0091] In this calculation model, in addition to the real-time measured absorbance values , , and the pre-stored calibration coefficients X, Y, Z, F, it also includes some parameters related to sample preparation or measurement conditions, representing the volume of the extractant (such as tetrachloroethylene) used during sample extraction; representing the volume of the original water sample; D represents whether the extractant has been diluted before use and the dilution factor (if not diluted, then D = 1); representing the background concentration or absorbance correction value measured for the blank sample (i.e. pure extractant without oil or blank water sample processed through the same process), which is usually determined during calibration or zero-point calibration. The values of these parameters , , D, are usually known and can be input through the user interface or pre-set in the system settings.

[0092] In the execution of the calculation, the MCU will substitute the absorbance value obtained in the current measurement cycle , , , the stored calibration coefficients X, Y, Z, F, and the set sample parameters , , D, into the above-mentioned preset calculation model formula, and perform arithmetic operations. The final result of the operation represents the total concentration of oil substances in the original water sample to be measured, and the unit is milligrams per liter (mg / L).

[0093] After the calculation is completed, the obtained oil concentration value can be displayed in real time to the user through the display interface (such as the LCD screen) of the instrument, can be stored in the internal storage of the MCU to form a historical data record, or can be uploaded to the upper computer, PLC or data acquisition system through the communication interface (such as RS485, 4-20mA analog output, etc.) for process monitoring, data analysis or alarm control. Thus, a complete oil concentration measurement process is completed.

[0094] For example, three wavelengths of infrared LED light sources with wave numbers of , and are selected, the infrared LED light sources are driven with a pulse cycle as shown in Figure 2 , then the n-hexadecane standard solution, isooctane standard solution and benzene standard solution are automatically injected into the measurement tube in turn and their absorbance values for the above-mentioned wavelengths of infrared light are measured , , , and the above-mentioned absorbance measurement values are substituted into the formula:

[0095]

[0096] wherein, is the content of oil in tetrachloroethylene, and the unit is mg / L; , , are the absorbances measured at the corresponding wave numbers; X is a coefficient corresponding to the absorbance of the C—H bond in the CH2 group, mg / L / absorbance; Y is a coefficient corresponding to the absorbance of the C—H bond in the CH3 group, mg / L / absorbance; Z is a coefficient corresponding to the absorbance of the C—H bond in the aromatic ring, mg / L / absorbance; and F is a correction factor for the influence of aliphatic hydrocarbons on aromatic hydrocarbons, that is, the ratio of the absorbances of n-hexadecane at 2930 and 3030 .

[0097] First, the instrument needs to obtain the absorbance coefficients X, Y, Z, F by measuring standard solutions. Three sets of data can be obtained by measuring three standard solutions, and the values of the X, Y, Z absorbance coefficients can be obtained by solving equations. Since n-hexadecane and isooctane do not contain aromatic hydrocarbons, then Therefore, F can be obtained from the n-hexadecane standard solution and the isooctane standard solution 、 Measurement results calculation:

[0098]

[0099] The other three coefficients X, Y, Z can be obtained by simultaneously solving equations with the known concentrations of the three different standard solutions and the absorbance of the three different standard solutions under the above three infrared LED lights. After the four coefficients X, Y, Z, F are all obtained, the instrument automatically injects the sample to be measured into the measuring tube, measures the absorbance of the infrared light after extraction by tetrachloroethylene 、 、 , and the oil concentration calculation formula is:

[0100]

[0101] For example, see Figure 5 , Figure 5 An infrared oil measurement method system flowchart provided by the present application. The core controller microcontroller (MCU) generates a pulse width modulation (PWM) signal, which controls the infrared LED light source to emit pulsed infrared light through the constant current source generation circuit. The pulsed infrared light passes through the solution to be measured (the sample can be provided by a sampling device and processed by an extraction device), and the transmitted light is received by an infrared sensor. The electrical signal output by the sensor is processed in turn by a signal amplification circuit, a filter circuit, and an analog-to-digital (A / D) conversion circuit, and the final digital signal is fed back to the MCU. The MCU can also control the sampling device to sample the sample. The MCU performs subsequent processing based on the received digital signal, such as calculating the absorbance and the final oil concentration value. The entire process forms a closed loop operation under the control of the MCU.

[0102] In this way, the present application uses low-cost infrared light-emitting diodes (LEDs) instead of high-cost, complex infrared spectrometers used in traditional infrared photometric methods as light sources. At the same time, the supporting drive circuit and signal processing circuit are also relatively simplified, which greatly reduces the manufacturing cost of the entire oil measurement instrument, and the system structure is simpler and more compact, facilitating miniaturization and integration.

[0103] To address the potential issues of insufficient light intensity or damage from high currents when using LEDs directly, this application uses a pulse-width modulation (PWM) signal to control a constant current source to generate a constant peak current to pulse-drive infrared LEDs. This driving method allows for the application of peak currents far exceeding the DC rating within extremely short pulse widths, enabling the LED to instantaneously emit infrared light strong enough to meet the signal intensity required for quantitative measurement. Furthermore, the constant peak current design ensures the stability of the intensity of each light pulse, unaffected by minor fluctuations in the power supply voltage or the LED's own parameters.

[0104] Due to the use of pulse drive with a usually low duty cycle, the average power consumption and heat generation of the LED are effectively controlled, avoiding overheating, reduced efficiency and even damage caused by continuous high current operation, thereby improving the working reliability and service life of the infrared LED light source.

[0105] This method not only solves the problem of low-cost light sources, but also comprehensively processes multi-wavelength absorbance information by selecting at least three infrared LEDs that correspond to the characteristic absorption wavenumbers of oil substances, combining the Lambert-Beer law with a specific calculation model based on pre-calibrated coefficients. This allows the method to distinguish the contributions of different types of hydrocarbon groups and perform quantitative calculations. This enables the method to achieve the quantitative analysis accuracy required by traditional infrared photometry, rather than merely qualitative or semi-quantitative detection.

[0106] As an optional implementation, in order to further improve the stability and anti-interference ability of the measurement, the present application can also adopt a measurement scheme based on dual optical path differential. In this scheme, in addition to the sample optical path containing the solution to be tested (as described above for S101 and S102), the system also sets up a reference optical path in parallel. This reference optical path is intended to provide a baseline signal for real-time comparison with the sample optical path to eliminate interference with the measurement results caused by light source intensity fluctuations, detector response drift, circuit common-mode noise, and certain environmental factors (such as the general impact of temperature changes on optical components).

[0107] The construction of the reference optical path can be done in a variety of ways. For example, a reference cell with a structure similar to that of the sample measuring tube and the same optical path length can be set up, which is filled with a pure solvent that does not contain the oil substance to be measured (such as tetrachloroethylene used in sample extraction) or a specific reference liquid. At the same time, a corresponding infrared light source and receiver are also set on the reference optical path. Specifically, the same constant peak current as that used to drive the sample optical path LED (emitting the pulsed infrared light corresponding to the first electrical signal) is used to drive at least one (or a group, corresponding to multiple wave numbers) reference infrared LED lamp. The emission wave number of these reference infrared LED lamps is the same as that of the LED used in the sample optical path or is precisely matched (for example, also selected). 、 and LEDs). Reference pulses of infrared light emitted by the reference LEDs are guided through the reference optical path, e.g. through a reference cell filled with pure solvent. The corresponding optical design, which can require elements such as beam splitters, mirrors, lenses, etc., ensures that the optical conditions of the sample and reference optical paths are as consistent as possible (except for the sample itself).

[0108] To ensure the validity of the differential measurement, a microcontroller (MCU) is configured to synchronously control the infrared LEDs in the sample and reference optical paths to emit pulses of infrared light. This synchronization can be either driving the sample and reference LEDs of the same wavelength to emit light at the same time, or rapidly alternating the driving of the two at a very high frequency, such that the time difference between the two measurements is small enough to consider that both optical paths are measuring under approximately the same conditions. The MCU implements this synchronized driving by outputting synchronized PWM signals to the respective (or shared, but time- shared) constant current source circuits.

[0109] At the end of the reference optical path, an infrared light receiver is also provided, which should be strictly matched or calibrated with the receiver in the sample optical path, for receiving the reference pulses of infrared light transmitted through the reference optical path. This receiver converts the received light signal into a reference electrical signal corresponding to each of the pre-set characteristic absorption wavenumbers. This reference electrical signal mainly reflects the actual pulse intensity of the light source, the transmission characteristics of the optical path (without sample absorption), and the response characteristics of the detector.

[0110] Subsequently, the MCU receives the first electrical signal (digital signal after amplification, filtering, and A / D conversion) from the sample optical path and simultaneously receives the reference electrical signal (also processed and A / D converted) from the reference optical path. For each synchronized (or rapidly alternating) measurement pulse at each wavenumber, the MCU calculates a differential signal in real time based on these two signals. The differential signal can be calculated in various ways, such as the ratio (Ratio = first electrical signal / reference electrical signal) or difference (Difference = first electrical signal - reference electrical signal) of the two signal intensities. The ratio method can more directly reflect the transmittance or absorbance information of the sample.

[0111] Finally, and also a key step in the dual-path differential measurement, the subsequent absorbance calculation method changes. Instead of simply calculating the absorbance using the first electrical signal (sample signal) and the pre-stored baseline I0, the absorbance value is generated based on the sample signal (first electrical signal) processed using the just-calculated differential signal. For example, if the differential signal is calculated as a ratio , and the reference signal is considered to represent the effective incident light intensity (or a stable proportion thereof) at that moment, then the absorbance can be directly (or after simple conversion) calculated as Calculated. Wherein, The transmitted light intensity (or its A / D converted digital quantity) detected by the sample light path receiver at this wave number corresponds to the first electrical signal; in this way, before calculating the absorbance, the noise and drift components common to the two light paths have been effectively cancelled in the calculation of the difference signal, so that more stable and more accurate absorbance values are obtained These values will be used for the final concentration calculation in step S104. This differential measurement method significantly improves the instrument's ability to resist environmental interference and its own drift.

[0112] As an optional implementation, in order to further improve the measurement accuracy and stability of the oil measuring instrument in complex or changing environments, the present application also provides an implementation with adaptive adjustment capability.

[0113] Specifically, this implementation introduces one or more sensors for real-time monitoring of key parameters that can reflect the current sample light path measurement state and generating a feedback signal.

[0114] A preferred embodiment is to monitor the transmitted light intensity in the sample light path. For example, the first electrical signal (or the signal after S103 processing) output by the main infrared sensor of the sample light path (i.e. the infrared light receiver mentioned in S102) can be directly used as the feedback signal source; or, an additional dedicated light intensity monitoring element (such as a photosensitive diode, a photoresistor, etc.) can be set in the light path to generate an independent feedback signal. The amplitude or change of this feedback signal can reflect the fluctuation of the transmitted light intensity caused by factors such as changes in sample turbidity, slight shifts in the light path, aging of the light source, or window contamination.

[0115] The MCU continuously receives and processes this real-time feedback signal. The MCU runs a pre-set control algorithm inside, which is used to analyze the feedback signal and decide whether and how to make adaptive adjustments to the system parameters. Common examples of control algorithms include PID control algorithms. This algorithm compares the real-time monitored feedback signal value with a pre-set target value (for example, the expected transmitted light intensity level, which is usually set within the best linear response range of the detector), calculates the deviation, and according to the PID parameters, including the proportional coefficient Kp, the integral time Ti, and the derivative time Td, calculates the corresponding control output, which aims to drive the system to eliminate the deviation and make the feedback signal stable around the target value.

[0116] According to the output results of the control algorithm, the MCU will adaptively adjust at least one of the following system parameters to achieve closed-loop feedback control:

[0117] ​​Adjusting at least one optical path parameter of the sample optical path: in this adjustment mode, the system is equipped with actuators such as precision stepper motors, piezoelectric ceramic drivers or servo motors, etc. These actuators are configured to accurately adjust the position, angle or state of certain optical elements or mechanical components in the sample optical path. For example, the actuators can fine-tune the position of the measurement tube (sample cell) relative to the light beam, or adjust the focal length of the lenses, the angle of the mirrors, etc. in the optical path. The MCU issues instructions to the actuators according to the output of the control algorithm, driving them to make small physical adjustments, with the aim of compensating for optical path shifts or misalignments that may be caused by mechanical vibrations, thermal expansion and contraction, or sample flow, thereby optimizing the reception efficiency and stability of the optical signal.

[0118] Adjusting at least one parameter of the pulse width modulation signal to control the intensity of the light source: in this adjustment mode, the MCU directly adjusts the parameters of the PWM signal it generates itself to drive the infrared LED. The parameters that can be adjusted include, for example, the duty cycle or frequency of the PWM signal. By increasing the duty cycle or adjusting the frequency in some cases, the average current or peak current driving the LED can be increased (if the constant current source design allows a certain range of peak adjustment), thereby increasing the average emission intensity or peak intensity of the infrared LED. This adjustment mode is mainly used to compensate for excessive signal attenuation caused by excessive sample concentration or turbidity, or to compensate for the slow decline in light intensity of the LED light source itself due to aging, etc., with the aim of maintaining the signal intensity at the receiving end at a suitable level that is conducive to subsequent processing and calculation.

[0119] The system can be designed to mainly adopt one of the above two adjustment modes, or to intelligently select which adjustment mode to enable according to the characteristics of the feedback signal, the size or rate of change of the deviation. The introduction of this adaptive adjustment mechanism enables the oil measurement instrument to better adapt to changes in the sample and environment, maintaining the stability and accuracy of the measurement.

[0120] As an optional implementation, during actual measurement, especially when dealing with complex samples online, transient physical disturbances such as large bubbles, suspended solids or sudden changes in turbidity may be encountered, which can cause the transmitted light intensity to drop sharply, resulting in a false and non-real rapid increase in the absorbance value calculated according to the Lambert-Beer law, seriously affecting the accuracy of the measurement results. To solve this problem, the present application provides a specific processing method for distinguishing between real changes in oil concentration and transient physical disturbances.

[0121] The method is performed after the absorbance values corresponding to each pre-set characteristic absorption wavelength are obtained by step S103. First, the MCU monitors these absorbance values in real time, recording their changes over time. The MCU sets a pre-set threshold to determine whether the absorbance values have experienced a "rapid increase". This threshold can be set based on the absolute change in absorbance value, the relative change rate, or the change amplitude within a specified short time window.

[0122] When the MCU detects that the absorbance values of at least one wavelength have changed beyond the pre-set threshold within a short period of time (e.g., within a few measurement cycles), the system does not immediately consider this as an increase in oil concentration, but instead initiates an analysis program to determine the relative pattern of absorbance value changes at all three wavelengths during this rapid increase. This "relative change pattern" can refer to the proportional relationship of the absorbance increase values at each wavelength, or the combination of their dynamic curve shape characteristics over time.

[0123] Next, the MCU compares the currently observed "relative change pattern" with a pre-expected spectral absorption characteristic pattern representing the true change in oil concentration based on pre-set criteria. This pre-expected spectral absorption characteristic pattern is established based on the spectral characteristics of oil substances themselves, for example, under normal circumstances, when the oil concentration increases, and will significantly increase and maintain a certain proportional relationship, while increases relatively small or has a specific association with (facilitated by factor F).

[0124] The result of the comparison triggers the decision logic: in response to the currently observed "relative change pattern" not conforming to the expected oil spectral absorption characteristic pattern (e.g., finding that increases abnormally large, or the absorbance of the three wavelengths increases almost simultaneously and proportionally, which is more characteristic of non-selective blocking or scattering of light), the MCU determines that the current event is a transient physical disturbance. Conversely, in response to the currently observed "relative change pattern" conforming to the expected oil spectral absorption characteristic pattern, the MCU determines that it is a true change in oil concentration.

[0125] Finally, corresponding processing is performed according to the result of the determination. In response to determining that a transient physical disturbance has occurred, the MCU performs pre-set suppression or marking processing on the oil concentration results calculated based on these abnormal absorbance values during the duration of the disturbance. This processing can include: marking the calculated concentration values during this period as invalid data or "disturbance state", and distinguishing them when output or recorded; or maintaining the display of the last valid concentration measurement value until the disturbance is removed and the signal returns to normal; or not updating the concentration value, etc.

[0126] In this way, false high concentration alarms or records caused by physical interference such as large bubbles, instantaneous high turbidity, etc. can be effectively avoided, and the reliability of the measurement results can be significantly improved. Only when it is determined that the oil concentration has changed, the calculated concentration result is considered valid and is normally output or recorded.

[0127] As an optional embodiment, the present application provides a more precise interference determination method to further improve the identification accuracy of transient physical interference. After detecting a suspected interference condition of rapid and large increase in absorbance value, instead of directly comparing the relative change pattern of the absorbance itself, the frequency domain characteristics of the signal are analyzed in depth.

[0128] Specifically, when the judgment condition of suspected interference is triggered, the microcontroller (MCU) performs Fourier transform (e.g. fast Fourier transform FFT) on the first electric signal corresponding to the wave number in the time period when the "rapid increase" event occurs.

[0129] At this time, the electric signal subjected to Fourier transform is the digitized time series sample after A / D conversion.

[0130] The purpose of performing Fourier transform is to convert the time-domain signal into a frequency-domain representation, thereby obtaining a frequency spectrum containing the frequency components of the signal and their intensity and phase information. Since the present application uses pulsed infrared light, the frequency spectrum should contain significant components of the fundamental frequency of the driving LED pulse signal (f , determined by the PWM frequency) and its integer multiple harmonic frequencies (2 , 3 ,...).

[0131] Next, the MCU analyzes the calculated frequency spectrum to determine the amplitude and / or phase of the fundamental component of the pulse frequency (f ) and at least one of its harmonic components (e.g. second harmonic or third harmonic ). Based on these amplitude and phase information, parameters that can represent the "shape" or "structure" of the current pulse signal are calculated, which can be the amplitude ratio of the harmonic component to the fundamental component (e.g. ), and / or the relative phase relationship of the harmonic component to the fundamental component (e.g. ). These ratios and relationships together constitute the "harmonic structure characteristics" of the current signal.

[0132] Then, the MCU compares the current calculated amplitude ratio and / or relative phase relationship with a pre-set reference harmonic structure parameter, and generates a comparison result. This "reference harmonic structure parameter" represents the expected observed harmonic structure under normal measurement conditions or when the oil concentration has a real change. This reference parameter can be calculated theoretically, or more commonly, learned statistically from Fourier transform analysis of the signals of undisturbed standard samples of different concentrations during instrument calibration or running, and stored in the MCU.

[0133] Finally, based on the comparison result, the MCU determines whether a transient physical disturbance has occurred. The logic of the determination can be: if the currently calculated harmonic structure parameter (amplitude ratio and / or phase relationship) deviates significantly from the pre-set reference harmonic structure parameter (for example, the relative amplitude of a certain harmonic abnormally increases, or the phase relationship is severely distorted, beyond the pre-set tolerance range), it indicates that the received light pulse shape is severely disturbed, which is likely not caused by the change in oil concentration absorption, but by scattering, diffraction or blocking caused by bubbles, turbidity and other physical factors. In this case, the MCU determines that a transient physical disturbance has occurred. If the comparison result shows that the current harmonic structure is within the pre-set tolerance range and consistent with the reference parameter, it is considered that the signal change is mainly caused by absorption (or at least cannot be determined as disturbance by this method), and it is determined that no transient physical disturbance has occurred (or has not been detected). This determination result can be used to trigger subsequent processing steps.

[0134] This harmonic structure analysis-based method makes use of the deep information in the frequency domain of the signal, and is more sensitive and robust in distinguishing certain types of disturbances than the analysis based only on the time-domain absorbance pattern.

[0135] As an optional implementation, in order to realize more accurate, forward-looking and intelligent collaborative adjustment of the system parameters of the infrared oil measuring instrument, the application further proposes an implementation based on model predictive control. This method aims to predict the future effect of different control strategies, dynamically adjust and optimize the target according to the current system state, and select the optimal collaborative adjustment action to optimize the accuracy of subsequent oil concentration measurement and system stability.

[0136] In a specific implementation, the microcontroller MCU collects and constructs the current system state in real time. The current system state includes the current value of the feedback signal, the current value of the differential signal, the feedback signal change rate, the differential signal change rate, the determination result of whether transient physical interference occurs, and optionally, at least one or more combinations of the currently applied optical path parameter setting value and the pulse width modulation signal parameter setting value. The current value of the feedback signal and the current value of the differential signal reflect the current light intensity characteristics of the sample optical path and the reference optical path, respectively, and the change rate is obtained by the differential calculation of two adjacent measurement cycles. The transient physical interference determination result is derived from the output of the aforementioned absorbance change pattern analysis and spectrum structure analysis module.

[0137] Based on the current system state, the microcontroller generates several candidate coordinated adjustments. Each candidate coordinated adjustment comprises a set of proposed combinations of optical path parameter adjustments and pulse width modulation signal parameter adjustments, covering fine-tuning changes of varying magnitudes and directions, such as fine-tuning the optical path focus, fine-tuning the optical path length, and fine-tuning the pulse duty cycle or pulse frequency.

[0138] For each candidate coordinated adjustment, the microcontroller uses an internally stored state transition model to perform simulations based on the current system state. The state transition model is used to predict the evolution trend of the feedback signal, differential signal, and its rate of change in one or more future measurement cycles if a specific candidate coordinated adjustment is applied. Specifically, the state transition model uses a multivariate linear regression model trained based on historical system data, and its form includes but is not limited to:

[0139] Feedback signal next value = × Feedback signal current value + × Current value of differential signal + × Feedback signal change rate + × Differential signal change rate + ×Interference determination flag+ ×Optical path parameter adjustment amount+ × Pulse signal parameter adjustment amount + ;

[0140] Differential signal next step value = × Feedback signal current value + × Current value of differential signal + × Feedback signal change rate + × Differential signal change rate + ×Interference determination flag+ ×Optical path parameter adjustment amount+ × Pulse signal parameter adjustment amount + .

[0141] in, ~ 、 ~ 、 、 These are model coefficients obtained through least squares regression analysis during system calibration or commissioning. If the system design requires real-time adaptation to environmental changes, the state transition model can also be updated online during operation based on newly collected data, using sliding window regression or recursive least squares to adjust the coefficients in real time.

[0142] The simulation uses a forward recursive method. After each candidate coordinated adjustment is applied, the predicted values ​​of the feedback signal value, differential signal value, and their rate of change for the next N measurement cycles (e.g., N=3) are recursively calculated based on the aforementioned state transition model. The current system state is used as the initial condition during the simulation.

[0143] For each candidate coordinated adjustment variable, the microcontroller applies an optimization objective function based on the predicted future state. This optimization objective function aims to maximize the accuracy of future oil concentration calculations and typically comprises a weighted combination of signal strength stability, signal-to-noise ratio, and interference recovery speed. Under normal measurement conditions, the optimization objective function prioritizes maximizing the signal-to-noise ratio. Upon detecting transient physical interference, the optimization objective function dynamically adjusts to prioritize rapid recovery and stability.

[0144] By calculating the optimization objective function value for each candidate coordinated adjustment variable, the microcontroller selects the coordinated adjustment variable with the highest score as the adjustment action for this round. The microcontroller then generates specific execution instructions and sends them to the optical path adjustment actuator and pulse width modulation signal generation module, respectively, to update the system's optical path parameters and light source intensity parameters in real time.

[0145] The above-mentioned intelligent collaborative adjustment action based on model prediction is repeated periodically, enabling the infrared oil measuring instrument to continuously optimize its measurement conditions according to changes in the system operating status, thereby improving the accuracy, stability and anti-interference ability of the overall oil concentration measurement.

[0146] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

Claims

1. An infrared oil tester that drives an infrared LED lamp through a pulse signal, characterized in that: include: generating a pulse width modulation signal, and generating a constant peak current based on the pulse width modulation signal, and using the constant peak current to drive an infrared LED lamp with a preset characteristic absorption wave number to emit pulsed infrared light; guiding the pulsed infrared light to pass through a measuring tube containing a solution to be tested, receiving the pulsed infrared light transmitted through the solution to be tested, and converting the pulsed infrared light into a first electrical signal corresponding to each of the preset characteristic absorption wavenumbers; processing each of the first electrical signals to generate an absorbance value corresponding to each of the preset characteristic absorption wavenumbers; Calculating the oil concentration in the solution to be tested according to a preset calculation model based on the absorbance value and a pre-calibrated coefficient; The method further includes: monitoring the time variation of absorbance values ​​in real time; when detecting that at least one absorbance value has a rapid increase exceeding a preset threshold value within a preset short time window, determining a relative change pattern of the absorbance values ​​at each corresponding wavenumber during the rapid increase; Based on a preset criterion, the relative change pattern is compared with the expected spectral absorption characteristic pattern of the oil substance concentration change: In response to the relative change pattern not conforming to the expected spectral absorption characteristic pattern, determining that a transient physical interference has occurred; in response to the relative change pattern conforming to the expected spectral absorption characteristic pattern, determining that the oil concentration has actually changed; in response to determining that a transient physical interference has occurred, performing a preset suppression or marking process on the oil concentration result calculated based on the absorbance value during the rapid increase period; Determining the relative change pattern of the absorbance value at each corresponding wavenumber during the rapid increase period includes: Performing a Fourier transform on the first electrical signal corresponding to the wave number during the rapid increase to obtain a frequency spectrum including the pulse frequency of the pulsed infrared light and its harmonics; determining an amplitude ratio and / or a relative phase relationship between a fundamental component of the pulse frequency and at least one harmonic component thereof in the frequency spectrum; The currently determined amplitude ratio and / or relative phase relationship is compared with preset reference harmonic structure parameters to generate a comparison result; based on the comparison result, it is determined whether the transient physical interference occurs.

2. The infrared oil measuring instrument according to claim 1, wherein the infrared LED lamp is driven by a pulse signal. Also includes: Setting a reference optical path; Using the constant peak current to drive at least one reference infrared LED lamp corresponding to the preset characteristic absorption wavenumber to emit reference pulsed infrared light and guide it through the reference optical path; The microcontroller synchronously controls the infrared LED lamps of the sample light path and the reference light path to emit pulsed infrared light; receiving the reference pulse infrared light transmitted through the reference optical path and converting it into a reference electrical signal corresponding to each of the preset characteristic absorption wavenumbers; The microcontroller calculates a differential signal in real time based on the first electrical signal and the reference electrical signal; Based on the differential signal, each of the first electrical signals is processed to generate an absorbance value corresponding to each of the preset characteristic absorption wavenumbers.

3. The infrared oil measuring instrument according to claim 2, wherein the infrared LED lamp is driven by a pulse signal. Also includes: The feedback signal reflecting the intensity of the transmitted light in the sample light path is monitored in real time by the sensor; The microcontroller executes a control algorithm based on the feedback signal to adaptively adjust at least one of the following: adjusting at least one optical path parameter of the sample optical path by an actuator; At least one parameter of the pulse width modulation signal is adjusted to control the intensity of the light source.

4. The infrared oil measuring instrument according to claim 1, wherein the infrared LED lamp is driven by a pulse signal. Also includes: Before calculating the oil concentration in the solution to be tested, calibration is performed, the calibration comprising: For a standard solution of known concentration, do the following: Using the constant peak current to drive the infrared LED lamp to emit the pulsed infrared light; directing the pulsed infrared light through the measuring tube containing the standard solution; receiving the pulsed infrared light transmitted through the standard solution and converting it into corresponding standard solution electrical signals corresponding to each of the preset characteristic absorption wavenumbers; Processing the electrical signal of each standard solution to determine the absorbance value of the standard solution corresponding to each preset characteristic absorption wavenumber; Based on the known concentration of the standard solution and the determined absorbance value thereof, the pre-calibrated coefficient and the correction factor of the pre-calibrated coefficient are calculated.

5. The infrared oil measuring instrument according to claim 1, wherein the infrared LED lamp is driven by a pulse signal. The preset characteristic absorption wave number is 2930 , 2960 and 3030 ; The preset calculation model is: ， in, represents the calculated oil concentration, 、 、 Corresponding to 2930 , 2960 and 3030 The absorbance value measured at the wave number, X, Y, Z represent the pre-calibrated coefficients corresponding to the absorbance of the target chemical bond, F represents the correction factor of the pre-calibrated coefficients for the effect of aliphatic hydrocarbons on aromatic hydrocarbons, represents the volume of the extraction solution, represents the sample volume, D represents the dilution multiple of the extract, represents the blank sample concentration.

6. The infrared oil measuring instrument according to claim 3, wherein: Also includes: The microcontroller collaboratively adjusts the optical path parameters and the pulse width modulation signal parameters based on the feedback signal and the differential signal: Obtaining a current system state; wherein the current system state includes: a current value of the feedback signal, a current value of the differential signal, a rate of change of the feedback signal, a rate of change of the differential signal, a result of determining that transient physical interference has occurred, and at least one or a combination of multiple settings of the currently applied optical path parameters and the pulse width modulation signal parameters; For a set of candidate coordinated adjustment amounts, using a preset state transition model, based on the current system state, respectively predict the future state value of one or more measurement signal indicators after applying each candidate coordinated adjustment amount; Wherein, each of the candidate coordinated adjustment amounts comprises an adjustment combination of the optical path parameter and the pulse width modulation signal parameter; Determining an optimization objective function based on the current system state and evaluating future state values ​​corresponding to each candidate coordinated adjustment amount; wherein the optimization objective function is intended to maximize the accuracy of oil concentration calculation; The candidate coordinated adjustment amount that optimizes the optimization objective function is selected, and the actuator and the pulse width modulation signal are controlled based on the selected candidate coordinated adjustment amount.

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