Multi-channel gas Raman scattering detection device and detection method thereof

Abstract

The invention discloses a multichannel gas Raman scattering detection device and a detection method thereof, and belongs to the technical field of gas monitoring, the multichannel gas Raman scattering detection device comprises a laser, a multi-reflection cavity and a plurality of detection modules; the multi-reflection cavity is used as a gas cell, and a light window B of the multi-reflection cavity is opposite to a light window A of the laser; two oppositely arranged cavity mirrors are arranged in the internal space of the multi-reflection cavity; more than two light windows C are arranged at the focus of the multi-reflection cavity; the central axis of each light window C passes through the focus; the plurality of detection modules are in one-to-one correspondence with the light windows C; each detection module comprises a collection channel, a PMT and a counter; one end of the collection channel is communicated with the light window C, and the other end is communicated with the light window D of the PMT; a filter is arranged in the inner space of the collection channel; the counter is electrically connected with the PMT and used for processing signals generated by the PMT. The structure is simplified, the size and the manufacturing cost of the detection device are reduced, and the component information of the gas in the target scene can be detected, so that quantitative detection is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas detection, and in particular relates to a multi-channel gas Raman scattering detection device and a detection method thereof. Background Art

[0002] Existing gas Raman detection systems usually consist of a laser, a gas cell and a spectrometer. The gas Raman scattering signal is collected by a lens and focused to the incident port of the spectrometer. The gas Raman spectrum is generated by light splitting inside the spectrometer and detecting it with a CCD (Charge-Coupled Device). However, the spectrometer needs to measure Raman spectra of all wavelengths, so the spectrometer needs to be equipped with multiple optical elements and a loaded optical system. This complexity leads to a large size of the spectrometer, which in turn makes the structure of the entire gas Raman detection system complex, large in size and high in cost. Therefore, existing gas Raman detection systems can usually only be installed and used indoors or on-site as fixed equipment, which is not convenient for movement and carrying between different locations. Summary of the Invention

[0003] In view of this, the present invention provides a multi-channel gas Raman scattering detection device and a detection method thereof, which simplifies its structure, reduces the volume and cost of the detection device, and can detect the composition information of the gas in the target scene, thereby achieving quantitative detection.

[0004] The present invention is achieved through the following technical solutions:

[0005] A multi-channel gas Raman scattering detection device includes: a laser, a multi-reflection cavity and several detection modules;

[0006] The multi-reflection cavity serves as a gas pool, and the optical window B of the reflection cavity is arranged opposite to the optical window A of the laser. The internal space of the multi-reflection cavity is provided with two cavity mirrors arranged opposite to each other, so that the laser beams reflected by the cavity mirrors converge at the same focus. Two or more optical windows C are provided at the focus of the multi-reflection cavity; the central axis of each optical window C passes through the focus.

[0007] The plurality of detection modules correspond to the light windows C one by one; each detection module includes: a collection channel, a PMT and a counter;

[0008] One end of the collection channel is connected to the optical window C, and the other end is connected to the optical window D of the PMT; a filter is provided in the interior space of the collection channel for filtering signals other than the target wavelength;

[0009] The counter is electrically connected to the PMT and is used for processing the signal generated by the PMT.

[0010] Furthermore, each of the cavity mirrors is a concave mirror.

[0011] Furthermore, the multi-reflection cavity further includes: a housing A;

[0012] The light window B is mounted on the housing A, and the two cavity mirrors are arranged in the inner space of the housing A;

[0013] The housing A is also provided with an air inlet and an air outlet for the inlet and outlet of the gas to be detected.

[0014] Furthermore, the collecting channel further comprises: a housing B and two lenses;

[0015] The housing B is a cylindrical structure, coaxial with the light windows C and D;

[0016] The two lenses are arranged in the housing B, and the two lenses are coaxially spaced along the axial direction of the housing B;

[0017] Of the two lenses, the lens located at optical window C is used to collimate the optical signal, and the lens located at optical window D is used to focus the optical signal;

[0018] The filter is arranged between two lenses.

[0019] Furthermore, among the two or more detection modules, the collection channel of one detection module serves as a reference channel, and the reference channel measures the intensity of the scattered background light.

[0020] Furthermore, the detection device further comprises: a control circuit, a serial port screen and a laser driver board;

[0021] The control circuit includes: an MCU and a voltage conversion chip;

[0022] The voltage conversion chip is electrically connected to the MCU, PMT and counter to provide a suitable voltage;

[0023] The MCU is electrically connected to the counter and the serial port screen, and the processing result of the counter is transmitted to the MCU for processing and the data signal is transmitted to the serial port screen;

[0024] The laser driving board is electrically connected to the laser and is used to drive the laser to emit light stably.

[0025] Furthermore, the detection device further comprises: a bottom plate and a bracket;

[0026] The laser and the bracket are mounted on the bottom plate;

[0027] The multi-reflection cavity is installed on the top of the bracket;

[0028] The laser driving board is arranged in the space between the bracket and the bottom plate.

[0029] A multi-channel gas Raman scattering detection method, based on the multi-channel gas Raman scattering detection device, comprises the following steps:

[0030] Step 1: Issue commands through the serial port screen, and the commands are transmitted to the MCU for processing;

[0031] Step 2: Determine the instruction. If the instruction is to not start acquisition, return to the processing stage. If the instruction is to start acquisition, turn on the detection module. The PMT of the detection module collects the Raman signal of the target gas. The PMT converts the collected Raman signal into an electrical signal.

[0032] Step 3: First, the counter counts the count value of the corresponding electrical signal; the count value counted by each counter is transmitted to the MCU respectively;

[0033] Secondly, the MCU calculates the ratio of the count value of each collection channel corresponding to the target gas to the count value of the collection channel serving as the reference channel:

[0034]

[0035] Where Ci is the count value of the collection channel corresponding to the i-th target gas, Cref is the count value of the collection channel as the reference channel, and Ri is the ratio;

[0036] Finally, the ratio Ri is used as the original value, and the accurate target gas concentration is calculated and stored based on the original value;

[0037] Step 4: The stored gas concentration value is transmitted to the serial port screen to update the serial port screen data;

[0038] Step 5: When the serial port screen issues a stop acquisition command, the PMT stops acquiring and returns to step 1; when the serial port screen issues a command not to stop acquiring, it returns to step 3.

[0039] Beneficial effects:

[0040] (1) A multi-channel gas Raman scattering detection device of the present invention adopts a multiple reflection cavity as a gas pool, so that the laser beam is reflected multiple times in the cavity and focused on one point, thereby increasing the light intensity, and then effectively improving the signal strength, improving the detection accuracy and reliability; at the same time, more than two light windows C are provided at the focus of the multiple reflection cavity, and the central axis of each light window C passes through the focus, thereby ensuring the signal strength passing through each detection module, further enhancing the stability and reliability of the detection; in addition, the filter provided in the collection channel can filter the light signal (Raman signal) outside the target wavelength range, thereby obtaining pure signals of different target gases, further improving the accuracy of the detection; by using multiple PMTs to detect multiple target gases simultaneously, not only can the gas composition information in the target scene be quickly and accurately obtained and quantitatively detected, but the overall volume of the detection device is also reduced, achieving an efficient, compact and high-precision gas detection effect.

[0041] (2) In a multi-channel gas Raman scattering detection device of the present invention, the collecting channel further includes a housing B and two lenses. The lens located at the light window C collimates the light signal so that the light signal can pass through the filter vertically, ensuring the uniformity and consistency of the light signal when passing through the filter, effectively reducing the loss and scattering of the light signal, further improving the quality and intensity of the light signal, and providing a guarantee for subsequent detection; the lens located at the light window D focuses the light signal so that the light signal can be accurately focused on the receiving surface of the detection module, which not only further enhances the intensity of the light signal, but also improves the spatial resolution of the light signal, ensuring that the detection module can efficiently and accurately receive and convert the light signal, thereby improving the sensitivity and reliability of the detection.

[0042] (3) In a multi-channel gas Raman scattering detection device of the present invention, among two or more detection modules, the collection channel of one detection module serves as a reference channel, and the reference channel measures the intensity of scattered background light. By setting the reference channel, the influence of laser power fluctuation on the detection effect can be reduced, thereby ensuring the stability and accuracy of the detection results.

[0043] (4) In a multi-channel gas Raman scattering detection device of the present invention, the voltage conversion chip is electrically connected to the MCU, PMT and counter, ensuring that each component operates efficiently under a stable power supply; at the same time, the serial port screen simplifies the operation process, making it easier for operators to monitor and obtain detection results in real time.

[0044] (5) In a multi-channel gas Raman scattering detection device of the present invention, the laser driving board is arranged in the space between the bracket and the base plate, which further reduces the occupied space and is conducive to the miniaturization of the detection device.

[0045] (6) The multi-channel gas Raman scattering detection method of the present invention can simultaneously process the count values ​​of multiple collection channels, thereby realizing the detection of multiple target gas concentrations and ensuring the stability and accuracy of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the overall design diagram of the present invention;

[0047] Figure 2 This is a system optical path design diagram of the present invention;

[0048] Figure 3 This is a design diagram of the optical path portion of the present invention;

[0049] Figure 4 is a block diagram of the control circuit of the present invention;

[0050] Figure 5 MCU program flow chart of the present invention;

[0051] Among them, 1-base plate, 2-laser, 3-multi-reflection cavity, 301-housing A, 302-light window B, 303-cavity mirror, 4-collecting channel, 401-housing B, 402-lens, 403-filter, 5-PMT, 6-laser driver, 7-bracket. DETAILED DESCRIPTION

[0052] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0053] Example 1:

[0054] This embodiment provides a multi-channel gas Raman scattering detection device, such as Figure 1 and Figure 3 As shown (black arrows indicate circuits, yellow arrows indicate optical paths, and purple arrows indicate gas paths), it includes: a base plate 1, a control circuit, a laser 2, a multi-reflection cavity 3, a serial port screen (i.e., the display interface of the host computer), a laser driver board 6, and two or more detection modules;

[0055] The laser 2 is mounted on the base plate 1. In this embodiment, the thickness of the base plate 1 is preferably 10 mm to ensure the structural strength of the multi-channel gas Raman scattering detection device.

[0056] The multi-reflection cavity 3 is a gas pool and is installed on the bottom plate 1. The multi-reflection cavity 3 includes: a housing A301, a light window B302, two cavity mirrors 303 and two or more light windows C.

[0057] The housing A301 is provided with an air inlet and an air outlet (not shown in the drawings) for the inlet and outlet of the gas to be detected (the gas always flows); in this embodiment, the gas to be detected is sucked into the interior of the housing A301 through a sampling pump.

[0058] Light window B302 is provided on housing A301 and is coaxially arranged opposite to light window A of laser 2. Light window B302 is a focusing lens used to focus the laser beam emitted by laser 2 to a target position. The laser beam emitted by laser 2 excites the gas in housing A301, generating a Raman signal.

[0059] like Figure 2 As shown, two cavity mirrors 303 are arranged opposite to each other and installed in the internal space of the housing A301; both cavity mirrors 303 are concave mirrors, and the light beam focused by the light window B302 is emitted to one of the cavity mirrors 303 and reflected multiple times between the two cavity mirrors 303; the light beam after each reflection converges to the same focus, thereby increasing the laser intensity at the focus and further enhancing the Raman signal at the focus;

[0060] Two or more optical windows C are provided on the housing A301, and the central axis of each optical window C passes through the focal point; the Raman signal generated inside the housing A301 is emitted to the outside of the housing A301 through the optical window C;

[0061] A detection module is installed on each light window C in a one-to-one correspondence;

[0062] Each detection module includes: a collection channel 4, a PMT (Photomultiplier Tube) 5 and a counter;

[0063] The collection channel 4 is used to collect the corresponding Raman signal, including: a cylindrical housing B401, a filter 403 and two lenses 402;

[0064] like Figure 3 As shown, one end of the housing B401 is fixedly connected to the housing A301, and the other end is fixedly connected to the detection module; the housing B401 is coaxial with the corresponding optical window C and the optical window D of the PMT5;

[0065] The two lenses 402 and the filter 403 are installed in the housing B401;

[0066] The lenses 402 are all convex lenses, and the two lenses 402 are coaxially spaced apart along the axial direction of the housing B401, that is, one lens 402 is close to the light window C, and the other lens 402 is close to the light window D;

[0067] The filter 403 is used to filter Raman signals other than the target wavelength and is disposed between the two lenses 402;

[0068] In each detection module, the Raman signal enters the collection channel 4 through the optical window C and is incident on the first lens (lens B near the optical window C). The first lens collimates the Raman signal; the collimated Raman signal passes vertically through the filter 403, so that the Raman signal passes vertically through the filter 403, and the filter 403 filters the Raman signal except for the target wavelength range; the filtered Raman signal is incident on the second lens (lens B near the optical window D), and the second lens B focuses the filtered Raman signal to form a clear light spot, and finally enters the PMT 5 through the optical window D; the incident Raman signal is converted into an optical pulse voltage signal by the PMT 5;

[0069] As an example, among two or more detection modules, the collection channel of one detection module serves as a reference channel; the reference channel is used to measure the intensity of scattered background light, which can reduce the impact of laser power fluctuations on the detection effect, thereby ensuring the stability and accuracy of the detection results; the reference channel does not respond to the target gas;

[0070] The counter is connected to the PMT5 in a one-to-one correspondence, and the counter counts the number of pulse voltage signals detected per unit time (hereinafter described as count value);

[0071] The laser driving board 6 is mounted on the base plate 1 and is used to supply power to the control circuit, the counter and the laser 2;

[0072] As an example, the multi-channel gas Raman scattering detection device further includes: a bracket 7;

[0073] The bracket 7 is disposed on the base plate 1, and the multi-reflection cavity 3 is mounted on top of the bracket 7, thereby ensuring that the optical axis of the reflection cavity and the optical window A are placed on the same plane, while also ensuring the structural strength of the multi-channel gas Raman scattering detection device; the laser driving board 6 is located in the space between the bracket 7 and the base plate 1, thereby reducing the occupied space;

[0074] The control circuit is mounted on the base plate 1 (not shown in the drawings), and includes: a voltage conversion chip, an MCU (Microcontroller Unit) and a counter interface;

[0075] The voltage conversion chip is electrically connected to the MCU, PMT5 and counter to provide appropriate voltage (such as Figure 412V to 5V, 5V to 3.3V) to ensure stable operation at its rated voltage; in this embodiment, the voltage conversion chip is preferably AMS-1117; the voltage conversion chip and the counter are connected through the counter interface; in this embodiment, the counter interface corresponds to the counter one-to-one, and the counter interface adopts the RS232 model, and the interface chip adopts the MAX3232; the counter is electrically connected to the output end of the PMT5;

[0076] The MCU is electrically connected to all counters and the serial port screen. The MCU is provided with multiple serial ports, each of which corresponds to a counter, thereby distinguishing the data transmitted by each counter. The processing result (i.e., the count value) of each counter is transmitted to the MCU, which processes and calculates the corresponding target gas concentration. The serial port screen sends instructions to the MCU and receives data such as gas concentration from the MCU, and displays the received data. In this embodiment, the serial port screen uses a large-color seven-inch medical-grade resistive touch screen with an RS485 interface.

[0077] The MCU is electrically connected to the sampling pump to control the opening and closing of the sampling pump. As an example, the sampling pump uses a 5V relay, and the MCU outputs a 5V control signal to the relay, thereby controlling the closing or opening of the relay contacts to start or stop the sampling pump.

[0078] In this embodiment, the MCU is preferably GD32F103RCT6 which supports five UART (Universal Asynchronous Receiver / Transmitter) interfaces;

[0079] Example 2:

[0080] like Figure 5 As shown, based on Example 1, this embodiment provides a multi-channel gas Raman scattering detection method, which includes the following steps:

[0081] Step 1: Issue instructions

[0082] After the control circuit is initialized, the operator issues commands through the serial port screen, and the commands are transmitted to the MCU for processing;

[0083] Step 2: Determine the instruction and collect Raman signals

[0084] When the instruction is not to start acquisition, return to the processing stage;

[0085] When the instruction is to start acquisition, the detection module is turned on; the PMT5 of the detection module acquires the Raman signal of the target gas; the PMT5 converts the acquired Raman signal into an electrical signal;

[0086] Step 3: Data processing

[0087] First, the counter counts the number of corresponding electrical signals (i.e., counts the count value); the count value counted by each counter is transmitted to the MCU respectively;

[0088] Secondly, the MCU obtains the ratio of the count value of each collection channel 4 corresponding to the target gas to the count value of the collection channel 4 as the reference channel:

[0089]

[0090] Among them, C i is the count value of the collection channel 4 corresponding to the i-th target gas, C ref is the count value of collection channel 4 as the reference channel, R i is a ratio;

[0091] Finally, the ratio R i As the original value, the accurate target gas concentration is calculated and stored;

[0092] Step 4: Update the serial port screen

[0093] The stored gas concentration values ​​are transmitted to the serial port screen to update the serial port screen data;

[0094] Step 5: Determine the command and stop collecting

[0095] When the operator issues a stop acquisition command through the serial port screen, PMT5 stops acquisition and returns to the stage of processing the serial port screen command (i.e., step 1); when the serial port screen issues a command not to stop acquisition, it returns to the data processing stage (i.e., step 3).

[0096] Example 3:

[0097] This embodiment, based on embodiment 1, provides a multi-channel gas Raman scattering detection device for simultaneously detecting three gases, including: four detection modules;

[0098] The multi-reflection cavity 3 is provided with four light windows C, corresponding one to one with the four detection modules;

[0099] The four detection modules are arranged opposite to each other in pairs, with a 90° angle between each two adjacent detection modules;

[0100] Among the four detection modules, three detection modules are used to detect Raman signals of oxygen, nitrogen and hydrogen respectively, and the other detection module is used to measure a reference signal.

[0101] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-channel gas Raman scattering detection device, characterized in that: include: A laser (2), a multi-reflection cavity (3) and a plurality of detection modules; The multi-reflection cavity (3) serves as a gas pool, and the optical window B (301) of the reflection cavity (3) is arranged opposite to the optical window A of the laser; the internal space of the multi-reflection cavity (3) is provided with two cavity mirrors (303) arranged opposite to each other, so that the laser beams reflected by the cavity mirrors (303) converge at the same focus; more than two optical windows C are provided at the focus of the multi-reflection cavity (3); the central axis of each optical window C passes through the focus; The plurality of detection modules correspond to the light windows C one by one; each detection module comprises: a collection channel (4), a PMT (5) and a counter; One end of the collection channel (4) is connected to the optical window C, and the other end is connected to the optical window D of the PMT (5); a filter (403) is provided in the interior space of the collection channel (4) for filtering signals other than the target wavelength; The counter is electrically connected to the PMT (5) and is used for processing the signal generated by the PMT (5).

2. A multi-channel gas Raman scattering detection device as claimed in claim 1, characterized in that: Each cavity mirror (303) is a concave mirror.

3. The multi-channel gas Raman scattering detection device according to claim 1, characterized in that: The multi-reflection cavity (3) further includes: a housing A (301); The light window B (301) is mounted on the housing A (301), and the two cavity mirrors (303) are arranged in the inner space of the housing A (301); The housing A (301) is also provided with an air inlet and an air outlet for the inlet and outlet of the gas to be detected.

4. A multi-channel gas Raman scattering detection device as claimed in claim 3, characterized in that: The collecting channel (4) further comprises: a housing B (401) and two lenses (402); The housing B (401) is a cylindrical structure, coaxial with the light windows C and D; The two lenses (402) are arranged in the housing B (401), and the two lenses (402) are coaxially spaced apart along the axial direction of the housing B (401); Of the two lenses (402), the lens (402) located at the optical window C is used to collimate the optical signal, and the lens (402) located at the optical window D is used to focus the optical signal; The filter (403) is arranged between the two lenses (402).

5. The multi-channel gas Raman scattering detection device according to claim 1, characterized in that: Among the two or more detection modules, the collection channel of one detection module serves as a reference channel, and the reference channel measures the intensity of the scattered background light.

6. A multi-channel gas Raman scattering detection device according to any one of claims 1 to 5, characterized in that: The detection device also includes: a control circuit, a serial port screen and a laser driver board (6); The control circuit includes: an MCU and a voltage conversion chip; The voltage conversion chip is electrically connected to the MCU, the PMT (5) and the counter, and is used to provide a suitable voltage; The MCU is electrically connected to the counter and the serial port screen, and the processing result of the counter is transmitted to the MCU for processing and the data signal is transmitted to the serial port screen; The laser driving board (6) is electrically connected to the laser (2) and is used to drive the laser (2) to emit light stably.

7. A multi-channel gas Raman scattering detection device as claimed in claim 6, characterized in that: The detection device further comprises: a base plate (1) and a bracket (7); The laser (2) and the bracket (7) are mounted on the base plate (1); The multi-reflection cavity (3) is mounted on the top of the bracket (7); The laser driving board (6) is arranged in the space between the bracket (7) and the bottom plate (1).

8. A multi-channel gas Raman scattering detection method, based on the multi-channel gas Raman scattering detection device of claim 6 or 7, characterized in that: The following steps are involved: Step 1: Issue commands through the serial port screen, and the commands are transmitted to the MCU for processing; Step 2, judging the instruction, when the instruction is not to start the collection, returning to the processing stage; when the instruction is to start the collection, turning on the detection module, and the PMT (5) of the detection module collects the Raman signal of the target gas; the PMT (5) converts the collected Raman signal into an electrical signal; Step 3: First, the counter counts the count value of the corresponding electrical signal; the count value counted by each counter is transmitted to the MCU respectively; Secondly, the MCU obtains the ratio of the count value of each collection channel (4) corresponding to the target gas to the count value of the collection channel (4) serving as the reference channel: Among them, C i is the count value of the collection channel (4) corresponding to the i-th target gas, C ref is the count value of the collection channel (4) as the reference channel, R i is a ratio; Finally, the ratio Ri is used as the original value, and the accurate target gas concentration is calculated and stored based on the original value; Step 4: The stored gas concentration value is transmitted to the serial port screen to update the serial port screen data; Step 5: When the serial port screen issues a command to stop collecting, PMT (5) stops collecting and returns to step 1; when the serial port screen issues a command not to stop collecting, it returns to step 3.

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