Carbon monoxide detection method and system

Abstract

The invention provides a carbon monoxide detection method and system. The system comprises a light path module and a detection module, the light path module comprises a laser configured to send a detection light signal to a gas absorption cell; the detector is arranged on a light path of the laser and is configured to convert a detection light signal into a current signal; the detection module comprises a transimpedance amplifier configured to convert a current signal into a voltage signal; the gain amplifier is connected with the transimpedance amplifier and is configured to amplify the voltage signal; the analog-to-digital conversion module is configured to convert the amplified voltage signal into a digital signal; the core processor is connected with the analog-to-digital conversion module and is configured to calculate the concentration of carbon monoxide based on the digital signal. The circuit design of the system does not need an external power supply management circuit, one detection module can meet the requirement of circuit hardware required by carbon monoxide detection, and the system has the advantages of high stability, high integration level, small size, low cost and low power consumption.

Description

Technical Field

[0001] The present application relates to the technical field of laser gas analysis instruments, and in particular to a carbon monoxide detection method and system. Background Art

[0002] In the safety monitoring system data of coal mines, carbon monoxide concentration is one of the important signs for monitoring fires in coal mines. When drilling holes in the transport tunnel of coal mines, dry drilling can easily cause combustion in the holes, resulting in the emergence of a large amount of carbon monoxide, which can easily lead to carbon monoxide poisoning accidents. Therefore, it is necessary to monitor the mine environment to prevent carbon monoxide poisoning.

[0003] The current mainstream carbon monoxide sensor is a sensor based on the electrochemical principle, which has the advantages of small size, light weight and low cost. However, electrochemical carbon monoxide sensors will have problems such as zero drift, inaccurate accuracy and short service life as the use time increases, and the impact can only be reduced through regular calibration. In some usage scenarios, the calibration of carbon monoxide sensors is inconvenient, which affects gas monitoring applications. There is an urgent need for a carbon monoxide sensor design method that can overcome the above problems.

[0004] Laser carbon monoxide detection modules based on tunable diode laser absorption spectroscopy (TDLAS) can avoid the above problems and are not subject to cross-interference from other gases. Laser carbon monoxide detection modules are generally composed of lasers, detectors, gas absorption cells and gas detection circuits. The gas detection circuit includes power management circuits, laser drive circuits, laser temperature control circuits, analog signal conversion circuits and main control chips. In existing product designs, most discrete devices are used. For example, the current signal is converted into a voltage signal through an operational amplifier; the gain adjustment function is achieved by adjusting the resistance value in the proportional amplifier circuit in the operational amplifier amplifier through a potentiometer; the temperature control of the laser is achieved through a voltage comparator implemented through an operational amplifier; and the temperature calculation compensation is achieved through a temperature sensor. Such a trimming method requires the addition of more peripheral circuits, including multiple operational amplifiers, multiple potentiometers, etc. The circuit design is relatively complex, which is not conducive to the miniaturization design and cost control of the sensor, and the stability is also low during use. Summary of the invention

[0005] The present application provides a carbon monoxide detection method and system to solve the technical problems of the existing sensor circuit design being complex, not conducive to miniaturization design, high cost and poor stability.

[0006] The first aspect of the present application provides a carbon monoxide detection system, including an optical path module and a detection module; the optical path module includes: a laser, configured to send a detection light signal to a gas absorption cell; wherein the gas absorption cell includes carbon monoxide; a detector, arranged on the optical path of the laser, configured to convert the detection light signal into a current signal; the detection module includes: a transimpedance amplifier, configured to convert the current signal into a voltage signal; a gain amplifier, connected to the transimpedance amplifier, configured to amplify the voltage signal; an analog-to-digital conversion module, connected to the gain amplifier, configured to convert the amplified voltage signal into a digital signal; a core processor, connected to the analog-to-digital conversion module, configured to calculate the concentration of carbon monoxide based on the digital signal.

[0007] In some feasible implementations, the core processor is further configured to tune the amplification factor of the voltage signal by the gain amplifier according to the digital signal.

[0008] In some feasible implementations, the optical path module also includes: the detection module also includes a first digital-to-analog conversion module, connected to the core processor; the core processor is also configured to control the first digital-to-analog conversion module to send a first voltage according to the digital signal; the detection module also includes: a voltage-to-current conversion circuit, connected to the laser, and the voltage-to-current conversion circuit is configured to output current to the laser according to the first voltage.

[0009] In some feasible implementations, the detection module also includes a second digital-to-analog conversion module, which is connected to the core processor; the core processor is also configured to control the second digital-to-analog conversion module to send a second voltage according to the digital signal; the detection module also includes a semiconductor refrigerator, a thermistor, a voltage comparator and a voltage-to-current conversion circuit; wherein the semiconductor refrigerator and the thermistor are arranged on the laser, the first end of the voltage comparator is connected to the semiconductor refrigerator through a voltage-to-current converter, the second end of the voltage comparator is connected to the second digital-to-analog conversion module, and the third end of the voltage comparator is connected to the thermistor; the thermistor is configured to send a third voltage; the voltage comparator is configured to output a fourth voltage according to the second voltage and the third voltage; the voltage-to-current conversion circuit is configured to output a control current according to the fourth voltage, and the control current is used to control the working state of the semiconductor refrigerator.

[0010] In some feasible implementations, the detection module further includes: a temperature sensor connected to the core processor and configured to obtain the ambient temperature; the core processor is further configured to perform temperature compensation on the laser according to the ambient temperature.

[0011] In some feasible implementations, the temperature compensation range is -40°C to 85°C, and the accuracy is ±1°C.

[0012] In some feasible implementations, the detection module further includes: a low voltage dropout linear regulator configured to provide a voltage input.

[0013] In some feasible implementations, the voltage is 3.6V to 5.5V.

[0014] In some feasible implementations, the core processor is further configured to adjust the output wavelength of the laser according to the driving current, and the driving current is positively correlated with the output wavelength.

[0015] The carbon monoxide detection system provided in the first aspect of the present application has a circuit design that does not require an external power management circuit, laser drive current and analog signal conversion circuit. These functions are all integrated in the detection module, so that one detection module can meet the circuit hardware requirements required for carbon monoxide detection, and has the advantages of high stability, high integration, small size, low cost and low power consumption.

[0016] The second aspect of the present application provides a carbon monoxide detection method, which is applied to the carbon monoxide detection system provided in the first aspect. The carbon monoxide detection method includes a laser sending a detection light signal to a gas absorption cell; a detector converting the detection light signal into a current signal; a transimpedance amplifier converting the current signal into a voltage signal; a gain amplifier amplifying the voltage signal; an analog-to-digital conversion module converting the amplified voltage signal into a digital signal; and a core processor calculating the concentration of carbon monoxide based on the digital signal.

[0017] The carbon monoxide detection method provided in the second aspect of the present application is applied in the carbon monoxide detection system provided in the first aspect, so its beneficial technical effects can be referred to the first aspect and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 is a structural schematic diagram of a carbon monoxide detection system provided in an embodiment of the present application;

[0020] Figure 2 It is a flow chart of a carbon monoxide detection method provided in an embodiment of the present application.

[0021] Graphic marking:

[0022] 100-Carbon monoxide detection system;

[0023] 10-optical path module; 11-laser; 12-gas absorption cell; 13-detector; 14-first voltage-current conversion circuit; 15-semiconductor refrigerator; 16-thermistor; 17-voltage comparator; 171-first end; 172-second end; 173-third end; 18-second voltage-current conversion circuit;

[0024] 20 - detection module; 21 - transimpedance amplifier; 22 - gain amplifier; 23 - analog-to-digital conversion module; 24 - core processor; 25 - first digital-to-analog conversion module; 26 - second digital-to-analog conversion module; 27 - temperature sensor; 28 - low voltage drop linear regulator. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by ordinary technicians in this field without making creative work all belong to the protection scope of the present application.

[0026] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0027] In addition, in the present application, directional terms such as "upper", "lower", "inner" and "outer" are defined relative to the orientation of the components schematically placed in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the orientation of the components placed in the drawings.

[0028] In order to solve the technical problems in the prior art that the circuit design is complex, which is not conducive to the miniaturization design and cost control of the sensor, and the stability during use is also low, the embodiment of the present application provides a carbon monoxide detection system, provides an innovative circuit design method, and has the characteristics of high stability, high integration, small size, low cost and low power consumption.

[0029] See also Figure 1 The carbon monoxide detection system 100 provided in the embodiment of the present application includes an optical path module 10 and a detection module 20 .

[0030] The optical path module 10 includes a laser 11 , a gas absorption cell 12 , a detector 13 , a first voltage-current conversion circuit 14 , a semiconductor refrigerator 15 , a thermistor 16 , a voltage comparator 17 and a second voltage-current conversion circuit 18 .

[0031] The laser 11 is used to send detection light to the gas absorption cell 12 , wherein the detection light carries a detection light signal, wherein the gas absorption cell 12 is arranged on the optical path of the laser 11 , and the gas absorption cell 12 contains carbon monoxide gas.

[0032] The detector 13 is arranged on the optical path of the laser 11 and is used to convert the detection light signal into a current signal. The detector 13 may be a photoelectric detector.

[0033] The detection module 20 includes a transimpedance amplifier 21 , a gain amplifier 22 , an analog-to-digital conversion module 23 , a core processor 24 , a first digital-to-analog conversion module 25 , a second digital-to-analog conversion module 26 , a temperature sensor 27 and a low-dropout linear regulator 28 .

[0034] The transimpedance amplifier 21 is used to convert the current signal into a voltage signal.

[0035] Specifically, the transimpedance amplifier 21 is used to convert the signal type.

[0036] The gain amplifier 22 is connected to the transimpedance amplifier 21 and is used to amplify the voltage signal.

[0037] Specifically, the gain amplifier 22 has a programmable function.

[0038] The analog-to-digital conversion module 23 is connected to the gain amplifier 22 and is used to convert the amplified voltage signal into a digital signal.

[0039] Specifically, the analog-to-digital conversion module 23 is used to convert the signal type.

[0040] The core processor 24 is connected to the analog-to-digital conversion module 23 and is used to calculate the concentration of carbon monoxide based on the digital signal. The core processor 24 is also used to tune the amplification factor of the voltage signal by the gain amplifier 22 according to the digital signal.

[0041] The first digital-to-analog conversion module 25 is connected to the core processor 24 , and the core processor 24 is further configured to control the first digital-to-analog conversion module 25 to send a first voltage according to the digital signal.

[0042] The first voltage-to-current conversion circuit 14 is connected to the laser 11. The first voltage-to-current conversion circuit 14 is used to output a first current to the laser 11 according to the first voltage. The first current is used to control the working state of the laser 11, wherein the working state may include the state of the laser 11 when it outputs different parameters during operation, for example, the state when it outputs different wavelengths.

[0043] In some embodiments, the core processor 24 is further configured to adjust the output wavelength of the laser 11 according to the first current, and the first current is positively correlated with the output wavelength. For example, the larger the first current, the larger the output wavelength.

[0044] The second digital-to-analog conversion module 26 is connected to the core processor 24, and the core processor 24 is further configured to control the second digital-to-analog conversion module 26 to send a second voltage according to the digital signal.

[0045] The semiconductor refrigerator 15 and the thermistor 16 are arranged on the laser 11, so that the temperature of the laser 11 can be detected in real time by the thermistor 16, and the temperature of the laser 11 can be adjusted by the semiconductor refrigerator 15. The voltage comparison circuit includes a first terminal 171, a second terminal 172 and a third terminal 173, wherein the first terminal 171 is connected to the semiconductor refrigerator 15 through the second voltage-current conversion circuit 18, the second terminal 172 is connected to the second digital-to-analog conversion module 26, and the third terminal 173 is connected to the thermistor 16. The thermistor 16 is used to output a third voltage.

[0046] The voltage comparator 17 is used to output a fourth voltage according to the second voltage and the third voltage, wherein the fourth voltage may be a difference between the second voltage and the third voltage.

[0047] The second voltage-current conversion circuit 18 is used to output a second current according to the fourth voltage, and the second current is used to control the working state of the semiconductor refrigerator 15. The working state of the semiconductor refrigerator 15 includes cooling or heating.

[0048] The temperature sensor 27 is connected to the core processor 24. The temperature sensor 27 is used to obtain the ambient temperature. The core processor 24 is also used to compensate the laser 11 according to the ambient temperature.

[0049] The low dropout linear regulator 28 is used to provide a wider voltage input.

[0050] Specifically, the detection module 20 can be understood as a chip with high integration functions.

[0051] In order to better understand the carbon monoxide detection system 100 provided in the embodiment of the present application, the working process of the carbon monoxide detection system 100 is briefly introduced below.

[0052] First, the 16-bit high-precision first digital-to-analog conversion module 25 integrated in the detection module 20 outputs a voltage signal at a frequency of 50kHz. The voltage analog quantity output by the first digital-to-analog conversion module 25 is proportionally converted into a first current of the current analog quantity through the first voltage-to-current conversion circuit 14 of the optical path module 10. The amplitude of this first current is used to tune the wavelength and optical power of the light emitted by the laser 11.

[0053] The thermistor 16 is arranged on the laser 11 and can be used as a reference for the temperature of the laser 11. A voltage is applied to one end of the thermistor 16, and a voltage divider resistor is arranged at the other end to output a third voltage. When the resistance of the thermistor 16 changes with temperature, the third voltage will also change accordingly. The second digital-to-analog conversion module 26 integrated in the detection module 20 outputs a second voltage, and the external voltage comparator 17 composed of an operational amplifier outputs the second voltage to the second voltage-current conversion circuit 18 according to the voltage difference between the second voltage and the third voltage, and tunes the second current output to the semiconductor refrigerator 15. The semiconductor refrigerator 15 adjusts the overall temperature of the laser 11 according to the direction and magnitude of the second current, thereby adjusting the wavelength and optical power of the laser 11. The direction of the second current can represent the cooling operation and heating operation of the semiconductor refrigerator 15. For example, the forward direction of the second current can represent the heating operation of the semiconductor refrigerator 15, and the reverse direction of the second current can represent the cooling operation of the semiconductor refrigerator 15.

[0054] The temperature sensor 27 integrated in the detection module 20 is used to achieve temperature compensation, and can achieve temperature detection with an accuracy of ±1°C within the range of -40°C to 85°C. When the temperature characteristic of the laser 11 is abnormal, the temperature control module setting temperature of the laser 11 can be adjusted according to the temperature sensor 27.

[0055] After temperature control and current tuning, the laser 11 can emit a narrowband laser of about 4.2 μm. Carbon monoxide gas molecules strongly absorb this wavelength band. The laser light source passes through the gas to be tested in the gas absorption cell 12 and is received by the detector 13. The optical power-wavelength curve in the detected light signal represents the absorption intensity of the gas to be tested in the gas absorption cell 12 for a specific spectrum. The core processor 24 integrated in the detection module 20 performs fitting calculation on the spectral absorption intensity information to invert the gas concentration in the gas absorption cell 12.

[0056] Under the action of the photoelectric effect, the detector 13 converts the received laser into current in proportion, and converts the detected light signal into a current signal. The transimpedance amplifier 21 integrated in the detection module 20 converts the current signal into a voltage signal, and the conversion ratio is determined by the resistance value of the externally configurable gain resistor. The programmable gain amplifier 22 integrated in the detection module 20 adjusts the voltage signal to an appropriate voltage range, and the adjustment ratio is determined by the core processor 24.

[0057] The 16-bit analog-to-digital conversion module 23 integrated in the detection module 20 collects and converts the voltage signal of the detector 13 after tuning through the transimpedance amplifier 21 and the programmable gain amplifier 22 into a digital signal, and the acquisition speed can reach 175ksps. The core processor 24 of the detection module 20 calculates the gas concentration in the gas absorption cell 12.

[0058] In addition, a low voltage dropout linear regulator 28 is integrated inside the detection module 20, and the power supply can be used in a wide voltage range of 3.6V to 5.5V.

[0059] In the carbon monoxide detection system 100 provided in the embodiment of the present application, the overall power supply of the detection module 20 can be powered by 2.7V~5.5V, of which 2.7V~3.6V can be directly input into the detection module 20 for use, and 3.6V~5.5V can be used after being stepped down by the built-in low-voltage difference linear regulator 28 of the detection module 20. In the working process, the core processor 24 first calculates the current and temperature parameters required for the operation of the laser 11 at the current ambient temperature, outputs the second voltage through the second digital-to-analog conversion module 26, and according to the third voltage output by the thermistor 16, the voltage comparator 17 outputs the fourth voltage according to the second voltage and the third voltage, which is converted into the second current and flows to the semiconductor refrigerator 15. The semiconductor refrigerator 15 starts to heat or cool. Since the thermistor 16, the semiconductor refrigerator 15, and the laser 11 are packaged together, the heat conduction is fast and the temperature is similar. Therefore, the laser 11 reaches the steady state of the set temperature through the negative feedback regulation of the voltage divider of the thermistor 16. Then, the first digital-to-analog conversion module 25 outputs a number of fine-tuned incremental first voltages, which are converted into current progressive scanning after circuit processing. At this time, the light emission wavelength of the laser 11 changes with the increase of the first current until the entire absorption peak band of carbon monoxide is covered. After passing through the gas absorption cell 12, the tuned laser spot is irradiated on the photosensitive surface of the detector 13, and a current with a proportional relationship is released based on the photoelectric effect. The detection module 20 has a built-in transimpedance amplifier 21 and a programmable gain amplifier 22 to convert this current into a voltage value in a suitable range. The built-in analog-to-digital conversion module 23 of the detection module 20 performs high-frequency acquisition, and the collected voltage value is fitted and filtered multiple times to calculate the gas concentration.

[0060] The circuit design of the carbon monoxide detection system 100 does not require an external power management circuit, and the functions of the laser 11 driving current and analog signal conversion circuit are integrated in the detection module 20, so that one detection module 20 can meet the circuit hardware requirements for carbon monoxide detection. It has the advantages of high stability, high integration, small size, low cost and low power consumption.

[0061] Corresponding to the above-mentioned carbon monoxide detection system embodiment, the present application also provides an embodiment of a carbon monoxide detection method. The carbon monoxide detection method is applied in the carbon monoxide detection system provided in the above-mentioned embodiment.

[0062] See also Figure 2 The carbon monoxide detection method can be implemented by the following steps S100 to S600.

[0063] Step S100: The laser sends a detection light signal to the gas absorption cell.

[0064] The carbon monoxide detection system provided by the above embodiment is adopted, and the detection light sent by the laser is controlled by the first current, and the detection light carries the detection light signal. Wherein, the gas absorption cell is arranged on the optical path of the laser, and the gas absorption cell contains carbon monoxide gas.

[0065] Step S200: The detector converts the detected light signal into a current signal.

[0066] The detector is a photodetector, which is used to convert the detected light signal into a current signal.

[0067] Step S300: The transimpedance amplifier converts the current signal into a voltage signal.

[0068] Transimpedance amplifiers are used to convert signal types.

[0069] Step S400: the gain amplifier amplifies the voltage signal.

[0070] Step S500: the analog-to-digital conversion module converts the amplified voltage signal into a digital signal.

[0071] The first digital signal carries the concentration information of carbon monoxide gas.

[0072] Step S600: The core processor calculates the concentration of carbon monoxide based on the digital signal.

[0073] The concentration of carbon monoxide is calculated based on the data of the entire absorption peak of carbon monoxide.

[0074] It should be noted that those skilled in the art will easily think of other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variation, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

[0075] It should be understood that the present application is not limited to the precise construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof, the true scope being indicated by the present application.

Claims

1. A carbon monoxide detection system, characterized in that: Including optical path module and detection module; The optical path module comprises: A laser is configured to send a detection light signal to a gas absorption cell; wherein the gas absorption cell contains carbon monoxide; a detector, disposed on the optical path of the laser, and configured to convert the detection light signal into a current signal; The detection module comprises: a transimpedance amplifier configured to convert the current signal into a voltage signal; a gain amplifier, connected to the transimpedance amplifier and configured to amplify the voltage signal; an analog-to-digital conversion module, connected to the gain amplifier, and configured to convert the amplified voltage signal into a digital signal; The core processor is connected to the analog-to-digital conversion module and is configured to calculate the concentration of carbon monoxide based on the digital signal.

2. The carbon monoxide detection system according to claim 1, characterized in that: The core processor is further configured to tune an amplification factor of the voltage signal by the gain amplifier according to a digital signal.

3. The carbon monoxide detection system according to claim 2, characterized in that: The detection module also includes a first digital-to-analog conversion module connected to the core processor; The core processor is further configured to control the first digital-to-analog conversion module to send a first voltage according to the digital signal; The optical path module also includes: A first voltage-to-current conversion circuit is connected to the laser. The first voltage-to-current conversion circuit is configured to output a first current to the laser according to the first voltage. The first current is used to control the working state of the laser.

4. The carbon monoxide detection system according to claim 3, characterized in that: The detection module also includes a second digital-to-analog conversion module connected to the core processor; The core processor is further configured to control the second digital-to-analog conversion module to send a second voltage according to the digital signal; The optical path module also includes a semiconductor refrigerator, a thermistor, a voltage comparator and a second voltage-current conversion circuit; wherein the semiconductor refrigerator and the thermistor are arranged on the laser, the first end of the voltage comparator is connected to the semiconductor refrigerator through the second voltage-current converter, the second end of the voltage comparator is connected to the second digital-to-analog conversion module, and the third end of the voltage comparator is connected to the thermistor; The thermistor is configured to transmit a third voltage; The voltage comparator is configured to output a fourth voltage according to the second voltage and the third voltage; The second voltage-current conversion circuit is configured to output a second current according to the fourth voltage, and the second current is used to control the working state of the semiconductor refrigerator.

5. The carbon monoxide detection system according to claim 4, characterized in that: The detection module also includes: The temperature sensor is connected to the core processor and is configured to obtain the ambient temperature. The core processor is also configured to perform temperature compensation on the laser according to the ambient temperature.

6. The carbon monoxide detection system according to claim 5, characterized in that: The temperature compensation range is -40°C to 85°C, and the accuracy is ±1°C.

7. The carbon monoxide detection system according to claim 1, characterized in that: The detection module also includes: A low dropout linear regulator is configured to provide a voltage input.

8. The carbon monoxide detection system according to claim 6, characterized in that: The voltage is 3.6V to 5.5V.

9. The carbon monoxide detection system according to claim 3, characterized in that: The core processor is further configured to adjust an output wavelength of the laser according to the first current, wherein the first current is positively correlated with the output wavelength.

10. A method for detecting carbon monoxide, characterized in that: In the carbon monoxide detection system according to any one of claims 1 to 9, the carbon monoxide detection method comprises: The laser sends a detection light signal to the gas absorption cell; The detector converts the detection light signal into a current signal; The transimpedance amplifier converts the current signal into a voltage signal; The gain amplifier amplifies the voltage signal; The analog-to-digital conversion module converts the amplified voltage signal into a digital signal; The core processor calculates the concentration of carbon monoxide based on the digital signal.

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