Gas detection method and device for infrared gas analyzer

Abstract

The invention relates to the technical field of gas detection, and discloses a gas detection method and device for an infrared gas analyzer, and the method comprises the steps: obtaining the light cutting frequency of a light cutting device, capturing a photoelectric signal according to the light cutting frequency, determining a square wave signal, and if the square wave signal triggers an interrupt signal, judging a sampling mark of the infrared gas analyzer, if the sampling mark is true, a capacitance detector is called in a preset sampling period to convert the light quantity difference between the measuring gas chamber and the reference gas chamber into an electric signal; the sampling mark is changed to be false, the interrupt signal is eliminated, the electric signal is subjected to fast Fourier transform algorithm calculation to obtain a target signal amplitude value, the target gas concentration of the detected gas is obtained through the target signal amplitude value and a preset corresponding relation, and the preset corresponding relation represents the corresponding relation between the signal amplitude value and the gas concentration; the gas detection method for the infrared gas analyzer, which is more practical and more accurate, is provided by the method.

Description

Technical Field

[0001] The present application relates to the technical field of gas detection, and in particular to a gas detection method and device for an infrared gas analyzer. Background Art

[0002] As an advanced detection equipment, infrared gas analyzer uses the principle of infrared absorption to achieve rapid and accurate analysis of gas components. It is widely used in industrial production, environmental monitoring and other fields, and plays an important role. In the operation mechanism of infrared gas analyzer, the signal generated by the detector due to the rotation of the motor-driven cutter is an AC signal. In view of this feature, most infrared gas analyzers on the market currently use two signal processing methods: one is to demodulate using hardware circuits and directly perform analog-to-digital conversion (ADC) sampling on the demodulated signal. Another method is to sample the AC signal and demodulate the AC signal using a digital algorithm.

[0003] Most infrared gas analyzers in the related art use the first hardware circuit demodulation method. However, although the traditional hardware circuit demodulation method is mature in technology, it has the problems of complex circuit design and high hardware cost. In addition, in the actual operation of the infrared gas analyzer, in order to ensure the measurement accuracy, it is necessary to ensure that the light area of ​​the light path passing through the windows on both sides of the detector chamber is equal. This optical path balance adjustment process is crucial. Traditional optical path balance adjustment not only requires independent circuits to realize the adjustment and measurement functions, but also requires switching between adjustment and measurement. The operation is complicated and relies on the assistance of external measurement tools (such as multimeters), which greatly increases the difficulty and time cost of operation. Obviously, there is an urgent need for a new gas detection method for infrared gas analyzers to solve at least one of the above problems.

[0004] It should be noted that the above content only provides background technical information related to the present application and does not necessarily constitute prior art. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present application provides a gas detection method and device for an infrared gas analyzer to reduce the operational difficulty of gas detection through an infrared gas analyzer and improve the efficiency and accuracy of gas detection.

[0006] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by the practice of the present application.

[0007] According to one aspect of an embodiment of the present application, a gas detection method for an infrared gas analyzer is provided, comprising: obtaining a cutoff frequency of a cutoff device, wherein the cutoff device is used to convert infrared light generated by an infrared light source into pulsed infrared radiation according to the cutoff frequency; capturing a photoelectric signal according to the cutoff frequency to determine a square wave signal; if the square wave signal triggers an interrupt signal, judging a sampling flag of the infrared gas analyzer; if the sampling flag is true, calling a capacitance detector to convert an electrical signal of a light quantity difference between a measuring gas chamber and a reference gas chamber within a preset sampling period; and changing the sampling flag to false, and clearing the interrupt signal; performing a fast Fourier transform algorithm on the electrical signal to obtain a target signal amplitude, and obtaining a target gas concentration of the measured gas through the target signal amplitude and a preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

[0008] In one embodiment of the present application, based on the above-mentioned solution, after determining the sampling flag of the infrared gas analyzer, the method further includes: if the sampling flag is false, clearing the interrupt signal.

[0009] In one embodiment of the present application, based on the aforementioned scheme, the method further includes: if it is monitored that the infrared gas analyzer is powered on, initializing the infrared gas analyzer; after initialization, periodically checking the infrared gas analyzer, and after the check passes, obtaining the cutting frequency of the cutting device.

[0010] In one embodiment of the present application, based on the aforementioned scheme, the preset corresponding relationship is determined in the following manner: a plurality of sample data and a plurality of test data are obtained, wherein the sample data includes a sample signal amplitude and a sample gas concentration corresponding to the sample signal amplitude, and the test data includes a test signal amplitude and a test gas concentration corresponding to the test signal amplitude; the preset corresponding relationship is established based on each of the sample signal amplitudes and the sample gas concentration corresponding to each of the sample signal amplitudes; and the preset corresponding relationship is verified by each of the test signal amplitudes and the test gas concentration corresponding to each of the test signal amplitudes.

[0011] In one embodiment of the present application, based on the aforementioned scheme, the method also includes: obtaining the current temperature of the capacitance detector; calculating a temperature difference based on the current temperature and a preset temperature; if the temperature difference is greater than the preset temperature difference, controlling the temperature of the capacitance detector through a temperature control module until the temperature difference is less than or equal to the preset temperature.

[0012] In one embodiment of the present application, based on the aforementioned scheme, the method also includes: obtaining the current pressure of the measuring air chamber; calculating a pressure difference based on the current pressure and a preset pressure; if the pressure difference is greater than the preset pressure difference, performing pressure control on the measuring air chamber based on the pressure difference through a pressure control module.

[0013] In one embodiment of the present application, based on the aforementioned scheme, after the electrical signal is subjected to a fast Fourier transform algorithm to calculate the target signal amplitude, the method further includes: displaying the calculated target signal amplitude through a display module; based on the target signal amplitude displayed by the display module, adjusting the target signal amplitude to the target value to adjust the optical path balance.

[0014] According to one aspect of an embodiment of the present application, a gas detection device for an infrared gas analyzer is provided, comprising: an acquisition module, for acquiring a cutoff frequency of a cutoff device, wherein the cutoff device is used to convert infrared light generated by an infrared light source into pulsed infrared radiation according to the cutoff frequency; a determination module, for capturing a photoelectric signal according to the cutoff frequency and determining a square wave signal; a judgment module, for judging a sampling flag of the infrared gas analyzer if the square wave signal triggers an interrupt signal; a calling module, for calling a capacitance detector to convert an electrical signal obtained by converting the light quantity difference between a measuring gas chamber and a reference gas chamber within a preset sampling period if the sampling flag is true; and changing the sampling flag to false and clearing the interrupt signal; a calculation module, for performing a fast Fourier transform algorithm on the electrical signal to obtain a target signal amplitude, and obtaining a target gas concentration of the measured gas through the target signal amplitude and a preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

[0015] The beneficial effects of the present application are as follows: the present application obtains the light cutting frequency of the light cutting device, captures the photoelectric signal according to the light cutting frequency, determines the square wave signal, and if the square wave signal triggers the interrupt signal, judges the sampling flag of the infrared gas analyzer, and if the sampling flag is true, calls the capacitance detector within the preset sampling period to convert the light quantity difference between the measuring gas chamber and the reference gas chamber into an electrical signal; and changes the sampling flag to false, and clears the interrupt signal, performs fast Fourier transform algorithm on the electrical signal to obtain the target signal amplitude, and obtains the target gas concentration of the measured gas through the target signal amplitude and the preset corresponding relationship, wherein the preset corresponding relationship characterizes the corresponding relationship between the signal amplitude and the gas concentration, reduces the operational difficulty of gas detection through the infrared gas analyzer, and improves the efficiency and accuracy of gas detection.

[0016] In addition, the present application can simplify the detection process and the calculation process, speed up the sampling speed, and thus improve the calculation efficiency and accuracy by synchronously sampling the electrical signal of the capacitance detector of the infrared gas analyzer. The present application also calculates the gas concentration of the measured gas faster and better by establishing a corresponding relationship between the signal amplitude and the gas concentration. By locally controlling the temperature of the capacitance detector and collecting the pressure signal for air pressure compensation, the accuracy and stability of the measurement results can be improved.

[0017] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0019] Figure 1 is a schematic diagram of an exemplary system architecture shown in an exemplary embodiment of the present application;

[0020] Figure 2 is a flow chart of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application;

[0021] Figure 3 It is a main flow diagram of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application;

[0022] Figure 4 It is a schematic diagram of a synchronous sampling process of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application;

[0023] Figure 5 It is a schematic diagram of a temperature control flow of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application;

[0024] Figure 6 It is a block diagram of a gas detection device for an infrared gas analyzer shown in an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0025] The following will describe the implementation methods of the present application with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, not for limiting the scope of protection of the present application.

[0026] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present application in a schematic manner, and therefore the illustrations only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0027] In the following description, a large number of details are discussed to provide a more thorough explanation of the embodiments of the present application. However, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present application difficult to understand.

[0028] First of all, it should be noted that the infrared gas analyzer uses infrared rays to analyze gases. It is an analysis method based on the selective absorption of infrared light by the measured gas components, and belongs to the molecular absorption spectroscopy analysis method. The light source emits infrared light in a certain wavelength range, and the cutter rotates periodically under the rotation of the synchronous motor, cutting the infrared light according to a certain period (that is, continuously and periodically blocking the light source), so that the infrared light becomes pulsed infrared radiation, which reaches the detector after passing through the measuring gas chamber and the reference gas chamber. The measuring gas chamber is continuously fed with the measured gas, and the reference gas chamber is filled with non-absorbent background gas. During operation, when the concentration of the measured gas in the measuring gas chamber changes, the amount of absorbed infrared light will change accordingly, while the amount of light of the reference beam (reference gas chamber beam) will not change. The difference in the amount of light coming out of the two chambers passes through the detector, causing the detector to generate a pressure difference and become an electrical signal of the capacitive detector. This signal is amplified and processed by the signal conditioning circuit and sent to the control unit for processing. The size of the output signal is proportional to the concentration of the measured gas component.

[0029] In infrared gas analyzers, due to the action of the motor and the cutter, the signal generated by the detector is an AC signal. There are two ways to collect AC signals. One is to demodulate using a hardware circuit and directly sample the demodulated signal using an ADC. Another way is to sample the AC signal and demodulate it using a digital algorithm. Currently, most infrared gas analyzers use the first hardware circuit demodulation method.

[0030] Most of the current infrared gas analyzers use hardware circuits to demodulate the AC signal of the detector, perform ADC sampling on the demodulated signal, and establish a mathematical relationship between the ADC sampling value and the gas concentration value to calculate the gas concentration. Using hardware circuits to demodulate signals is complex in circuit implementation and has high hardware costs.

[0031] When measuring, the infrared gas analyzer requires that the light path acts on the windows on both sides of the detector chamber with equal light areas. Before measuring, the light cutter needs to be adjusted to adjust the balance of the light path. The current infrared gas analyzer uses different circuits to adjust the light path balance part and the measurement part, which requires measurement switching and the use of measuring tools such as multimeters. The light path balance adjustment method is complicated and the operation steps are cumbersome.

[0032] DSP (Digital Signal Processing) is an emerging discipline that involves many disciplines and is widely used in many fields. Since the 1960s, with the rapid development of computer and information technology, digital signal processing technology has emerged and developed rapidly. Digital signal processing is a method of processing real signals represented by digital sequences by using mathematical techniques to perform conversions or extract information.

[0033] DSP (Digital Signal Processing) controller is a digital signal processor, which is mainly used to process digital signals, such as audio, image, video, etc. It is a high-speed processor. DSP controllers are mostly used in audio and video data processing, communication equipment and other fields.

[0034] MCU (Microcontroller Unit), also known as single chip microcomputer or single chip microcomputer, is a chip-level computer that appropriately reduces the frequency and specifications of the central processing unit (CPU) and integrates peripheral interfaces such as memory and timer on a single chip to provide different combination controls for different applications.

[0035] Converter chips include A / D converter chips and D / A converter chips. Analog-to-digital converter is A / D converter, or ADC for short. A stands for analog quantity and D stands for digital quantity. It usually refers to an electronic component that converts analog signals into digital signals. Digital-to-analog converter, also known as D / A converter, or DAC for short, is a device that converts digital quantities into analog ones.

[0036] The AD converter (ADC) usually converts analog quantity into digital quantity through four steps: sampling, holding, quantization and encoding. Sampling is to convert an analog quantity that changes continuously in time into an analog quantity that changes discretely in time. ADC (Analog-to-Digital Converter) is an analog-to-digital converter, which is a device or module that converts analog signals into digital signals. ADC samples analog signals at a certain frequency and discretizes continuous analog signals into discrete sampling values. The smaller the sampling period, the more sampling points, and the higher the sampling accuracy.

[0037] PID (Proportion Integral Differential) algorithm is a commonly used control algorithm. In process control, the PID controller (also known as PID regulator) that controls according to the proportion (P), integral (I) and differential (D) of the deviation is the most widely used automatic controller. It has the advantages of simple principle, easy implementation, wide application, independent control parameters, and relatively simple parameter selection. The basic principle of the PID control algorithm is to adjust the output control quantity according to the feedback signal so that the actual output of the system is as close to the expected output as possible. The PID controller consists of three control parts corresponding to the proportional, integral and derivative functions.

[0038] The FFT (Fast Fourier Transform) algorithm is an efficient frequency domain transformation algorithm. The FFT algorithm decomposes the original signal into smaller sub-problems, and then recursively applies the FFT algorithm to quickly calculate the signal's spectrum. Specifically, the FFT algorithm decomposes a signal of length N into two sub-signals of length N / 2, then performs a discrete Fourier transform (DFT) on each sub-signal, and finally combines the DFT results of the two sub-signals to obtain the final DFT result. This method significantly reduces the amount of calculation.

[0039] EEPROM (Electrically Erasable Programmable read only memory) is a memory chip that does not lose data after power failure. EEPROM can erase existing information and reprogram it on a computer or dedicated device. It is generally used in plug-and-play applications.

[0040] Figure 1 It is a schematic diagram of an exemplary system architecture shown in an exemplary embodiment of the present application.

[0041] Reference Figure 1 As shown, the system architecture may include a data acquisition device 101 and an MCU (Microcontroller Unit) device 102. The MCU device 102 may be at least one of a DSP, a single-chip microcomputer, an industrial computer, etc. The data acquisition device 101 is used to convert the signal of the thin film capacitor detector into an electrical signal that can be collected, and the MCU device 102 is used to obtain the cut-off frequency of the cut-off device, wherein the cut-off device is used to convert the infrared light generated by the infrared light source into pulsed infrared radiation according to the cut-off frequency. In this embodiment, the MCU device 102 processes the above data after the data acquisition device 101 obtains the above data. Relevant technicians can use the MCU device 102 to capture the photoelectric signal according to the cut-off frequency and determine the square wave signal. If the square wave signal triggers the interrupt signal, the sampling flag of the infrared gas analyzer is judged. If the sampling flag is true, the capacitance detector is called within the preset sampling period to convert the light quantity difference between the measurement gas chamber and the reference gas chamber into an electrical signal; and the sampling flag is changed to false, and the interrupt signal is cleared, and the electrical signal is calculated by the fast Fourier transform algorithm to obtain the target signal amplitude. The target gas concentration of the measured gas is obtained through the target signal amplitude and the preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration. It should be noted that the data acquisition device 101 and the MCU device 102 provided in this embodiment are only an example and should not bring any limitations to the functions and scope of use of the embodiments of the present application.

[0042] Figure 2 is a flow chart of a gas detection method for an infrared gas analyzer according to an exemplary embodiment of the present application. The gas detection method for an infrared gas analyzer can be executed by a computing and processing device, which can be Figure 1 MCU device 102 shown in FIG. Figure 2 As shown, the gas detection method for the infrared gas analyzer includes at least steps S210 to S250, which are described in detail as follows:

[0043] In step S210, a light cutting frequency of a light cutting device is obtained.

[0044] The light cutting device is used to convert the infrared light generated by the infrared light source into pulsed infrared radiation according to the light cutting frequency.

[0045] In step S220, the photoelectric signal is captured according to the light cutting frequency to determine a square wave signal.

[0046] In step S230, if the square wave signal triggers the interrupt signal, the sampling flag of the infrared gas analyzer is determined.

[0047] In step S240, if the sampling flag is true, the capacitance detector is called within the preset sampling period to convert the light quantity difference between the measuring gas chamber and the reference gas chamber into an electrical signal; the sampling flag is changed to false, and the interrupt signal is cleared. If the sampling flag is false, the interrupt signal is cleared.

[0048] In step S250, the electrical signal is subjected to a fast Fourier transform algorithm to obtain a target signal amplitude, and the target gas concentration of the measured gas is obtained through the target signal amplitude and a preset corresponding relationship.

[0049] The preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

[0050] In one embodiment of the present application, if it is monitored that the infrared gas analyzer is powered on, the infrared gas analyzer is initialized; after initialization, the infrared gas analyzer is periodically calibrated, and after the calibration passes, the cutting frequency of the cutting device is obtained.

[0051] In this embodiment, reference Figure 3 As shown, Figure 3 This is a schematic diagram of the main process of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application. After the infrared gas analyzer is powered on, a digital signal processor (DSP), such as DSP28335, i.e., 2TMS320F28335 digital signal processor, first completes the initialization of the system clock, I / O port lines (i.e., input / output port lines), various ADCs (analog-to-digital converters, i.e., A / D converters), serial ports, and EEPROM data reading. After the initialization is completed, the EEPROM data is periodically checked.

[0052] In one embodiment of the present application, a light-cutting piece driven by a synchronous motor is provided in the infrared gas analyzer as a light-cutting device, and a photoelectric sensor is provided on the rotation path of the light-cutting piece, so that the switching frequency of the photoelectric sensor is the same as the light-cutting frequency of the light-cutting piece, and a square wave signal is sent through the photoelectric sensor. The gas to be measured is input into the measuring gas chamber, and the background gas with no absorption properties is input into the reference gas chamber, and the light quantity difference between the measuring gas chamber and the reference gas chamber is converted into an electrical signal through a capacitance detector provided in the infrared gas analyzer. The light-cutting device rotates periodically under the rotation of the synchronous motor, continuously and periodically blocks the light source, cuts the infrared light according to a preset period, converts the infrared light into pulsed infrared radiation, and frequency modulates the infrared light, so that the signal generated by the capacitance detector is an AC signal.

[0053] In this embodiment, the ADC sampling rate, sampling points and FFT calculation points are designed according to the light-cutting frequency. The ADC chip is driven by the DSP controller, and the AC signal generated by the detector is synchronously collected by hardware synchronization using the light-cutting frequency.

[0054] In this embodiment, reference Figure 4 , Figure 4 This is a schematic diagram of the synchronous sampling process of the gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application. In the sensor data acquisition program design, the photoelectric signal generated by the motor cutting light is used as the sampling start flag to realize the synchronous sampling of the detector signal. The specific implementation method is as follows: determine whether the light cutting signal is captured. If the light cutting signal is captured, the square wave signal sent by the photoelectric sensor is used as the external interrupt source, waiting for the rising edge interrupt, and in the interrupt function, determine whether the sampling flag is true. If the data sampling flag, that is, the sampling flag, is true, determine to start sampling, turn on the timing and other periodic sampling, and set the sampling flag to false at the same time. Wait for data sampling. After the data sampling is completed and the calculation is completed, set the data sampling flag to true to start the next round of sampling calculation. If the data sampling flag is false, clear the interrupt flag, that is, the interrupt signal.

[0055] In this embodiment, the sampling period is set according to actual needs, and the sampling flag is set to true when there is no sampling, and the sampling flag is set to false when sampling is in progress. The square wave signal sent by the photoelectric sensor is used as the external interrupt source. At the beginning of each switching cycle of the square wave signal, the interrupt function is entered, and the rising edge of the square wave signal is used as the interrupt flag, and it is determined whether the sampling flag is true: if the sampling flag is true, the scheduled sampling is started according to the preset sampling period, and the data sampling flag is changed to false to avoid starting the next sampling before the current sampling is completed, so as to ensure the synchronization of data sampling; if the data sampling flag is false, the interrupt signal is cleared, the interrupt function is exited, and the next cycle of the square wave signal is continued to wait. After completing the data sampling and the calculation of the sampled data, the sampling flag is set to true to start the next cycle of sampling.

[0056] In one embodiment of the present application, the electrical signal is subjected to an FFT algorithm, i.e., a fast Fourier transform algorithm, to calculate the target signal amplitude, and the target gas concentration of the measured gas is calculated by the target signal amplitude and a preset corresponding relationship, so as to complete the gas detection of the measured gas. In this embodiment, the DSP control module, i.e., the DSP control period, uses the FFT algorithm to calculate the signal size of the detector. By calculating the amplitude of the corresponding frequency signal of the collected AC signal, i.e., the electrical signal, and combining the preset corresponding relationship that pre-established the mathematical relationship between the signal amplitude and the gas concentration, the gas concentration value is calculated, and the gas concentration value can be calculated faster and more accurately.

[0057] In one embodiment of the present application, the preset correspondence is determined in the following manner: a plurality of sample data and a plurality of test data are acquired, wherein the sample data includes a sample signal amplitude and a sample gas concentration corresponding to the sample signal amplitude, and the test data includes a test signal amplitude and a test gas concentration corresponding to the test signal amplitude; a preset correspondence is established based on each sample signal amplitude and a sample gas concentration corresponding to each sample signal amplitude; and the preset correspondence is verified by each test signal amplitude and a test gas concentration corresponding to each test signal amplitude.

[0058] In this embodiment, whether to adjust the preset corresponding relationship is determined based on the verification result. If the verification result is successful, it indicates that the preset corresponding relationship does not need to be adjusted, and the preset corresponding relationship is not adjusted; if the verification result is failed, the preset corresponding relationship is adjusted based on the test data. By establishing and verifying the preset corresponding relationship between the signal amplitude and the gas concentration, the direct corresponding relationship between the signal amplitude and the gas concentration can be better clarified, and the accuracy of the calculation results can be improved.

[0059] In one embodiment of the present application, the current temperature of the capacitor detector is obtained; the temperature difference is calculated based on the current temperature and the preset temperature; if the temperature difference is greater than the preset temperature difference, the temperature of the capacitor detector is controlled by the temperature control module until the temperature difference is less than or equal to the preset temperature.

[0060] In this embodiment, if the current temperature is lower than the preset temperature, and the temperature difference between the current temperature and the preset temperature is greater than the preset temperature difference, the capacitor detector is heated by the heating module of the temperature control module until the temperature difference is less than or equal to the preset temperature difference; if the current temperature is higher than the preset temperature, and the temperature difference is greater than the preset temperature difference, the capacitor detector is cooled by the cooling module of the temperature control module until the temperature difference is less than or equal to the preset temperature difference. Taking the preset temperature difference of 0 degrees as an example, if the current temperature is lower than the preset temperature, the capacitor detector is heated by the heating module of the temperature control module until the current temperature is equal to the preset temperature; if the current temperature is higher than the preset temperature, the capacitor detector is cooled by the cooling module of the temperature control module until the current temperature is equal to the preset temperature.

[0061] In this embodiment, in order to ensure the stability of the measurement results and reduce the impact of temperature on the measurement results, a PID (Proportional Integral Differential) control algorithm is used to implement local temperature control on the film capacitor receiver, i.e., the capacitor detector, so that the receiver is controlled at a stable temperature and the temperature drift of the receiver is reduced. Figure 5 , Figure 5 This is a schematic diagram of the temperature control flow of a gas detection method for an infrared gas analyzer shown in an exemplary embodiment of the present application. In order to reduce the impact of ambient temperature changes on the measurement results, the film capacitor receiver is temperature controlled. In the PID temperature control program design, a preset time (e.g., 1s) is set to perform a PID calculation, that is, a preset PID calculation time is set. The specific implementation method is as follows: determine whether the preset PID calculation time (e.g., 1S temperature control time) has arrived. If so, determine whether the register is wrong. If there is no error, that is, if it is determined that the AD setting of the collected temperature is correct, collect temperature data, use PID to calculate the heating amount, and use a digital-to-analog converter (DAC) such as DAC7513 to output the heating amount.

[0062] In one embodiment of the present application, in order to further ensure the stability of the measurement results and reduce the impact of temperature on the measurement results, the present application can also perform temperature control on the measurement chamber and the reference chamber. Obtain the first temperature of the measurement chamber and obtain the second temperature of the reference chamber; calculate the first temperature difference based on the first temperature and the preset first temperature, and calculate the second temperature difference based on the second temperature and the preset second temperature; if the first temperature difference is greater than the first preset temperature difference threshold, control the temperature of the measurement chamber through the first temperature control module until the first temperature difference is less than or equal to the first preset temperature difference threshold; if the second temperature difference is greater than the second preset temperature difference threshold, control the temperature of the reference chamber through the second temperature control module until the second temperature difference is less than or equal to the second preset temperature difference threshold.

[0063] In some embodiments, in order to ensure the overall stability of the infrared gas analyzer, it is sometimes necessary to control the temperature of the entire system; this usually involves installing a heating element or a cooling element inside the analyzer and adjusting its working state as needed to keep the temperature inside the system constant. In addition, the infrared light source is another key component of the infrared gas analyzer, which provides infrared light absorbed by the gas for measurement. However, the output of the infrared light source is affected by temperature, so when necessary, the infrared light source can also be temperature controlled.

[0064] In one embodiment of the present application, the current pressure of the measuring air chamber is obtained; the pressure difference is calculated based on the current pressure and the preset pressure; and pressure compensation is performed based on the pressure difference. The specific reference is as follows: if the pressure difference is greater than the preset pressure difference, the pressure control module performs pressure control on the measuring air chamber based on the pressure difference until the pressure difference is less than or equal to the preset pressure difference. The reference pressure of the reference air chamber is obtained; the reference pressure difference is calculated based on the reference pressure and the preset reference pressure; if the reference pressure difference is greater than the preset reference pressure difference, the reference pressure control module performs pressure control on the reference air chamber based on the reference pressure difference until the reference pressure difference is less than or equal to the preset reference pressure difference.

[0065] In this embodiment, if the current pressure of the measuring air chamber is greater than the preset pressure, and the pressure difference between the current pressure and the preset pressure is greater than the preset pressure difference, the pressure of the measuring air chamber is reduced based on the pressure difference by the pressure reduction module in the pressure control module until the pressure difference is less than or equal to the preset pressure difference; if the current pressure is less than the preset pressure, and the pressure difference is greater than the preset pressure difference, the pressure of the measuring air chamber is compensated based on the pressure difference by the pressure compensation module in the pressure control module until the pressure difference is less than or equal to the preset pressure difference. Taking the preset pressure difference as 0 as an example, if the current pressure of the measuring air chamber is greater than the preset pressure, the pressure of the measuring air chamber is reduced by the pressure reduction module in the pressure control module until the current pressure is equal to the preset pressure; if the current pressure is less than the preset pressure, the pressure of the measuring air chamber is compensated by the pressure compensation module in the pressure control module until the current pressure is equal to the preset pressure. The pressure control of the reference air chamber is similar, and will not be repeated here. The pressure control module including pressure compensation is used as an optional module. The pressure control module is turned on for the gas that needs pressure control to dynamically realize the pressure control of the gas, thereby avoiding the error in the measurement result caused by pressure change. For the gas that needs pressure compensation, the pressure compensation function is turned on, and for the gas that does not need pressure compensation, this function is turned off to dynamically realize the pressure compensation of the gas.

[0066] In one embodiment of the present application, the process after the electrical signal is subjected to a fast Fourier transform algorithm to calculate the target signal amplitude also includes the following steps: displaying the calculated target signal amplitude through a display module; based on the target signal amplitude displayed by the display module, adjusting the target signal amplitude to the target value to adjust the optical path balance.

[0067] In this embodiment, the calculated result, i.e., the target gas concentration, is transmitted to the HMI (Human-Machine Interface) display module by means of a preset serial communication interface standard, such as RS485 serial communication. When adjusting the optical path balance, it is only necessary to adjust the signal amplitude to the minimum by observing the signal amplitude on the HMI display screen. No external tools are required during the adjustment process, and the adjustment method is simple and convenient.

[0068] In one embodiment of the present application, the present application also provides an infrared gas analyzer control system to complete the process in the above embodiment. The infrared gas analyzer control system mainly realizes the acquisition and calculation of receiver signals. The control system is an important part of the infrared gas analyzer. Among them, the infrared gas analyzer control system mainly includes a core processing module, a receiver signal acquisition module, a frequency acquisition module, a temperature acquisition module, a PID temperature control module, a pressure data acquisition module, an EEPROM storage module, a communication module, etc., and the specific reference is as follows:

[0069] The core processing module uses DSP28335 as MCU, with an operating frequency of 150MHZ. DSP28335 is the core control module, which mainly realizes data collection, processing and calculation, and is the core component of the entire control system. The receiver signal acquisition module uses an analog-to-digital converter (ADC) such as the ADS1255 chip to design a suitable sampling frequency and collect the AC signal generated by the infrared film capacitor receiver; the frequency acquisition module uses the eCAP (enhanced capture) function of the DSP28335 to realize the frequency capture of the motor light-cutting signal, and uses hardware synchronization to realize the synchronous sampling of the infrared receiver signal; the temperature acquisition module uses an analog-to-digital converter (ADC) such as the ADS1220 chip to collect temperature data in real time; the PID temperature control module uses the PID control algorithm to control the heating output of the heating module according to the collected temperature data. The heating output is realized by the DAC chip to realize the local temperature control of the infrared receiver. The pressure data acquisition module uses a pressure measurement device such as an 85BSD digital pressure sensor to collect gas pressure data. The EEPROM storage module uses the 25LC640 chip to store important data. The communication module is divided into two paths, one of which communicates with the HMI display module to realize the transmission of measurement results and important parameters, using a first preset serial communication protocol such as MODBUS RTU; the other path communicates with the motor drive module to realize the effective control of the motor, using a second preset serial communication protocol such as MODBUS ASCII.

[0070] The system software design mainly includes main program design, sensor data acquisition program design, PID temperature control program design, etc. The main program operation flow chart is as follows Figure 3 As shown in the figure, after the system is powered on, DSP28335 first completes the initialization of system clock, I / O port lines, ADCs, serial ports, and EEPROM data reading. After the initialization is completed, the main function of the control system is entered.

[0071] The main function of the infrared gas analyzer control system mainly implements the following tasks: perform cyclic periodic verification of EEPROM data. Perform FFT operation on the collected receiver signal to calculate the gas concentration value. Collect temperature data in real time and use heating measures, and use PID control algorithm to realize local temperature control of the receiver. Collect gas pressure data and perform pressure compensation for gases that need pressure compensation. Perform data transmission with the motor control module. Perform data transmission with the HMI.

[0072] Understandably, Figure 3 The watchdog and feeding dog in the MCU system are important mechanisms for monitoring and ensuring the normal operation of the program. Through the monitoring of the watchdog and the operation of feeding the dog, the program can be effectively prevented from errors or falling into an infinite loop, thereby ensuring the stable operation of the MCU or system.

[0073] The present application provides a gas detection method for an infrared gas analyzer, which uses hardware synchronization technology to achieve synchronous sampling of detector data; uses the FFT algorithm for the sampled signal to calculate the signal amplitude, and combines the mathematical relationship between the signal amplitude and the gas concentration established in advance to calculate the concentration value; collects temperature data and uses the PID control algorithm to achieve local temperature control; collects gas pressure data and performs pressure compensation on the gas. The present invention has a simple circuit, low measurement cost, a simple method for adjusting the optical path balance, and more convenient measurement.

[0074] Figure 6 is a block diagram of a gas detection device for an infrared gas analyzer shown in an exemplary embodiment of the present application. The device can be applied to Figure 1 The implementation environment shown in the figure is specifically configured in the MCU device 102. The device can also be applied to other exemplary implementation environments and specifically configured in other devices. This embodiment does not limit the implementation environment to which the device is applied.

[0075] like Figure 6 As shown, the exemplary gas detection device for an infrared gas analyzer includes: an acquisition module 610 , a determination module 620 , a judgment module 630 , a calling module 640 and a calculation module 650 .

[0076] Among them, the acquisition module 610 is used to obtain the cut-off frequency of the cut-off device, wherein the cut-off device is used to convert the infrared light generated by the infrared light source into pulsed infrared radiation according to the cut-off frequency; the determination module 620 is used to capture the photoelectric signal according to the cut-off frequency and determine the square wave signal; the judgment module 630 is used to judge the sampling flag of the infrared gas analyzer if the square wave signal triggers the interrupt signal; the calling module 640 is used to call the capacitance detector to convert the light quantity difference between the measuring gas chamber and the reference gas chamber into an electrical signal within a preset sampling period if the sampling flag is true; and change the sampling flag to false and clear the interrupt signal; the calculation module 650 is used to calculate the target signal amplitude by fast Fourier transform algorithm on the electrical signal, and obtain the target gas concentration of the measured gas through the target signal amplitude and the preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

[0077] It should be noted that the gas detection device for infrared gas analyzer provided in the above embodiment and the gas detection method for infrared gas analyzer provided in the above embodiment belong to the same concept, wherein the specific manner in which each module and unit performs the operation has been described in detail in the method embodiment and will not be repeated here. In actual application, the gas detection device for infrared gas analyzer provided in the above embodiment can distribute the above functions to different functional modules as needed, that is, divide the internal structure of the device into different functional modules to complete all or part of the functions described above, and this is not limited here.

[0078] The flowchart and block diagram in the accompanying drawings illustrate the possible architecture, functions and operations of the system, method and computer program product according to various embodiments of the present application. Wherein, each box in the flowchart or block diagram can represent a module, a program segment, or a part of the code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0079] The units involved in the embodiments described in this application may be implemented by software or hardware, and the units described may also be set in a processor. The names of these units do not constitute limitations on the units themselves in some cases.

[0080] It should be noted that, although several modules or units of the equipment for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules or units described above can be embodied in one module or unit. On the contrary, the features and functions of one module or unit described above can be further divided into being embodied by multiple modules or units.

[0081] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the embodiments disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not disclosed in the present application.

[0082] The above embodiments are merely illustrative of the principles and effects of the present application, and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A gas detection method for an infrared gas analyzer, characterized in that: include: Acquiring a light cutting frequency of a light cutting device, wherein the light cutting device is used to convert the infrared light generated by the infrared light source into pulsed infrared radiation according to the light cutting frequency; Capturing the photoelectric signal according to the light-cutting frequency to determine the square wave signal; If the square wave signal triggers an interrupt signal, the sampling flag of the infrared gas analyzer is determined; If the sampling flag is true, the capacitance detector is called within a preset sampling period to convert the light quantity difference between the measuring gas chamber and the reference gas chamber into an electrical signal; the sampling flag is changed to false, and the interrupt signal is cleared; The electrical signal is subjected to a fast Fourier transform algorithm to calculate a target signal amplitude, and the target gas concentration of the measured gas is obtained through the target signal amplitude and a preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

2. The gas detection method for an infrared gas analyzer according to claim 1, characterized in that: After determining the sampling mark of the infrared gas analyzer, the method further includes: If the sampling flag is false, the interrupt signal is cleared.

3. The gas detection method for an infrared gas analyzer according to claim 1, characterized in that: The method further comprises: If it is monitored that the infrared gas analyzer is powered on, the infrared gas analyzer is initialized; after the initialization, the infrared gas analyzer is periodically calibrated, and after the calibration is passed, the light cutting frequency of the light cutting device is obtained.

4. The gas detection method for an infrared gas analyzer according to claim 1, characterized in that: The preset corresponding relationship is determined by: Acquire a plurality of sample data and a plurality of test data, wherein the sample data includes a sample signal amplitude and a sample gas concentration corresponding to the sample signal amplitude, and the test data includes a test signal amplitude and a test gas concentration corresponding to the test signal amplitude; Establishing the preset corresponding relationship based on each of the sample signal amplitudes and the sample gas concentration corresponding to each of the sample signal amplitudes; The preset corresponding relationship is verified by each of the test signal amplitudes and the test gas concentration corresponding to each of the test signal amplitudes.

5. The gas detection method for an infrared gas analyzer according to any one of claims 1 to 4, characterized in that: The method further comprises: Acquiring the current temperature of the capacitance detector; Calculate the temperature difference between the current temperature and the preset temperature; If the temperature difference is greater than the preset temperature difference, the temperature of the capacitance detector is controlled by a temperature control module until the temperature difference is less than or equal to the preset temperature.

6. The gas detection method for an infrared gas analyzer according to any one of claims 1 to 4, characterized in that: The method further comprises: Obtaining the current pressure of the measuring air chamber; Calculate the pressure difference according to the current pressure and the preset pressure; If the pressure difference is greater than the preset pressure difference, the pressure of the measuring air chamber is controlled based on the pressure difference by a pressure control module.

7. The gas detection method for an infrared gas analyzer according to any one of claims 1 to 4, characterized in that: After the electrical signal is calculated by a fast Fourier transform algorithm to obtain a target signal amplitude, the method further includes: The calculated target signal amplitude is displayed through a display module; Based on the target signal amplitude displayed by the display module, the target signal amplitude is adjusted to a target value to adjust the optical path balance.

8. A gas detection device for an infrared gas analyzer, characterized in that: include: An acquisition module, used for acquiring a light cutting frequency of a light cutting device, wherein the light cutting device is used for converting the infrared light generated by the infrared light source into pulsed infrared radiation according to the light cutting frequency; A determination module, used to capture the photoelectric signal according to the light-cutting frequency and determine the square wave signal; A judgment module, used for judging a sampling flag of the infrared gas analyzer if the square wave signal triggers an interrupt signal; A calling module, for calling the electrical signal converted by the capacitance detector from the light quantity difference between the measuring gas chamber and the reference gas chamber within a preset sampling period if the sampling flag is true; and changing the sampling flag to false, and clearing the interrupt signal; The calculation module is used to perform a fast Fourier transform algorithm on the electrical signal to obtain a target signal amplitude, and obtain a target gas concentration of the measured gas through the target signal amplitude and a preset corresponding relationship, wherein the preset corresponding relationship represents the corresponding relationship between the signal amplitude and the gas concentration.

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