Laser gas sensor module with ultra-wide concentration detection range

Abstract

The invention relates to the technical field of laser gas detection, and discloses a laser gas sensor module with an ultra-wide concentration detection range, which comprises a laser emitting unit for emitting tunable laser on the basis of a TDLAS (Tunable Diode Laser Absorption Spectroscopy) principle; the multi-node air chamber structure comprises at least one optical splitter and segmented optical paths. According to the laser gas sensor module with the ultra-wide concentration detection range, in order to expand the concentration detection range of a single gas sensor, a plurality of laser detection units with different absorption degrees are constructed by designing a plurality of sections of light paths and light splitting node structures in a gas chamber on the basis of a TDLAS (Tunable Diode Laser Absorption Spectroscopy) principle; according to the method, a plurality of gas concentration sensor units with different detection ranges are formed, a plurality of light detection units detect light signals of nodes respectively, and a processor processes detection data of the nodes at the same time and selects optimal data to calculate the concentration, so that the purpose that a single laser gas sensor covers the ultra-wide concentration detection range from 0.0001% to 100% is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser gas detection, in particular to a laser gas sensor module with an ultra-wide concentration detection range. Background Art

[0002] At present, gas sensors are widely used in smart homes, automotive electronics, industrial processes, environmental monitoring, consumer electronics and other occasions. In smart homes, gas sensors are used to detect indoor air quality, such as harmful gases such as gas, formaldehyde, carbon dioxide, ozone, etc., to ensure the health and safety of the living environment. In the field of automotive electronics, gas sensors are used to detect gas components in the car, such as oxygen, carbon dioxide, etc., to optimize the interior environment and provide safety. In industrial processes, gas sensors are used to monitor toxic and harmful gases in production operations, such as hydrogen sulfide and carbon monoxide, to ensure production safety. Environmental monitoring is one of the important application areas of gas sensors, which are used to detect pollutants in the air, such as methane, sulfur dioxide, nitrogen oxides, etc., to assess environmental quality. In consumer electronics, gas sensors are used to detect alcohol, carbon dioxide, etc., and are widely used in fields such as drunk driving detection and medical monitoring.

[0003] Gas sensors can be divided into electrochemical, semiconductor, infrared, catalytic combustion, laser gas sensors, etc. according to the detection principle. Each sensor has its own advantages and disadvantages. Electrochemical gas sensors can detect specific gases, have linear output, low power consumption, good resolution and accuracy, and are not interfered with by other gases, but have a limited operating temperature range, a short lifespan, and the longer the exposure time, the shorter the lifespan; semiconductor gas sensors are low-cost and fast-response, but are sensitive to humidity. Semiconductor gas sensors are low-cost, simple to manufacture, highly sensitive, fast-response, long-life, low-sensitivity to humidity, and have simple circuits, but must operate at high temperatures, have poor selectivity for gases or odors, dispersed component parameters, unsatisfactory stability, and high power consumption. Catalytic combustion enables the detection of combustible gases. Infrared sensors have high precision, good selectivity, high reliability, are not affected by oxygen, are less affected by environmental interference factors, and have a long lifespan, but they consume large power and are easily affected by dust and humidity.

[0004] Laser gas sensors use the wavelength tuning of semiconductor lasers and the selective absorption of the measured gas to measure gas concentration. They have the advantages of high sensitivity and high precision, high selectivity, long life, good stability, strong anti-interference, and the ability to achieve real-time, dynamic, and simultaneous multi-component measurement. However, their disadvantages are high cost and complex technology.

[0005] Since the degree of laser absorption is related to the gas concentration and the absorption time (optical path length), the higher the concentration, the stronger the absorption, and the longer the optical path, the stronger the absorption. Therefore, the gas concentration detection range coverage area is related to the optical path length. Short optical paths are suitable for high-concentration detection, and long optical paths are suitable for low-concentration detection. Therefore, different optical paths cover different ranges. The current detection equipment does not include sensors with multiple nodes across optical paths, and cannot well include multiple detection range areas, thereby failing to well expand the detection range of the sensor; it is not possible to complete the detection function of multiple sensors with only one laser light source and one gas chamber structure, thereby greatly reducing the volume and cost of ultra-wide range concentration detection. In view of this, we propose a laser gas sensor module with an ultra-wide concentration detection range. Summary of the Invention

[0006] The object of the present invention is to provide a laser gas sensor module with an ultra-wide concentration detection range to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A laser gas sensor module with an ultra-wide concentration detection range, based on the TDLAS principle, includes:

[0009] A laser emitting unit, configured to emit tunable laser light;

[0010] A multi-node air chamber structure includes at least one optical splitter and a segmented optical path, wherein the optical splitter splits the incident laser into two beams, one of which is transmitted to the optical signal detection unit, and the other continues to be transmitted along the optical path to the next optical splitting node;

[0011] Multiple optical detection units are installed behind each splitting node to detect the optical signal of each node. Since gas absorption is closely related to the laser wavelength and optical path length (absorption time), the gas concentration detected by nodes with different optical path lengths is different. The nodes at the end of the optical path detect the high concentration range, and the nodes with long optical paths detect the low concentration range.

[0012] The processor unit is used to receive data from each light detection unit, process multiple node detection data at the same time, perform concentration calculations respectively, and select appropriate node data as the final concentration calculation result according to the calculation results.

[0013] Preferably, the beam splitter can be realized by a coated beam splitter.

[0014] Preferably, the beam splitter can be realized by a prism structure.

[0015] Preferably, the node light detection unit is a linear detection unit, and its output voltage signal is linearly related to the laser power (mW).

[0016] Preferably, the splitting ratio of the node splitter can be designed according to actual needs. In general applications, the proportion of the light beam input to the light detection unit is low, and the light beam with a high proportion is transmitted to the next node, which can prevent the light detection unit from being saturated and ensure that the subsequent node has a higher effective optical signal.

[0017] Preferably, in the multi-node air chamber structure, since the optical path of the first node is the shortest and the gas absorption time is also the shortest, the laser absorption rate of the first node is the lowest, and the laser transmission distance of each node gradually increases thereafter, and the laser absorption rate gradually increases.

[0018] Preferably, the processor unit controls the laser die temperature, and the laser current is from I1 to I m Increase in steps and send periodically.

[0019] Preferably, the amplification factor of each node is adjusted so that the output voltage of each node is within the detection range of the processor and the amplitude of each node remains substantially consistent.

[0020] Preferably, each node data needs to be calibrated with standard concentration when performing concentration calculation, and the calibration parameters are saved. The processor unit calls the corresponding calibration parameters to perform concentration calculation based on the final selected node data to ensure that each node reports the gas concentration accurately within the valid data range.

[0021] Preferably, the processor unit makes a rationality judgment on each set of data based on data such as peak height and absorption peak width, and selects the optimal node data as the final concentration calculation data.

[0022] Compared with the prior art, the present invention provides a laser gas sensor module with an ultra-wide concentration detection range, which has the following beneficial effects:

[0023] 1. This ultra-wide concentration detection range laser gas sensor module, in order to expand the concentration detection range of a single gas sensor, designs multiple optical paths and splitting node structures in the gas chamber based on the TDLAS principle, constructs multiple laser detection units with different absorption degrees, and forms multiple gas concentration sensor units with different detection ranges. Multiple light detection units detect the light signal of each node respectively, and the processor simultaneously processes the detection data of multiple nodes and selects the optimal data to calculate the concentration, thereby achieving the purpose of a single laser gas sensor covering an ultra-wide concentration detection range from 0.0001% to 100%.

[0024] 2. In order to reduce the volume and cost of ultra-wide range concentration detection, this ultra-wide concentration detection range laser gas sensor module adopts only one laser light source and one gas chamber structure. The optical splitter in the gas chamber is used to split the laser into multiple beams, which are transmitted to the light detection units at different nodes for detection. Multiple light detection units are integrated into one sensor, thereby achieving the purpose of completing multiple sensor detection functions with only one set of equipment and reducing the detection volume and cost.

[0025] 3. In order to ensure that each node reports the gas concentration accurately within the valid data range, the ultra-wide concentration detection range laser gas sensor module performs standard concentration calibration and saves the calibration parameters when calculating the concentration through each node data. The processor unit calls the corresponding calibration parameters to calculate the concentration based on the final selected node data, thereby ensuring the accuracy of the concentration reporting of each node. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the overall functional structure diagram of the present invention;

[0027] Figure 2 This is a node gas absorption curve diagram assuming that the nodes have the same power after splitting;

[0028] Figure 3 This is a schematic structural diagram of a spectrometer according to the present invention;

[0029] Figure 4 Graph showing voltage signals at various nodes of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0032] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] See also Figure 1 - Figure 4 , the present invention provides a technical solution:

[0034] A laser gas sensor module with an ultra-wide concentration detection range, based on the TDLAS principle (this part of the function is a reference part of the present invention and its working principle is no longer described), includes: a laser emitting unit for emitting tunable laser; a multi-node gas chamber structure, including at least one optical splitter and a segmented optical path, the optical splitter can be realized by a coated optical splitter or a prism structure, the optical splitter divides the incident laser into two beams, one of which is transmitted to the optical signal detection unit, and the other continues to be transmitted along the optical path to the next optical splitting node; multiple optical detection units are respectively arranged behind each optical splitting node, and each node is detected by a plurality of optical detection units. The optical signal is used for detection. Since gas absorption is closely related to the laser wavelength and the optical path length (absorption time), the gas concentrations detected by nodes with different optical path lengths are different. The nodes at the end of the optical path detect the high concentration range, and the nodes with long optical paths detect the low concentration range. The processor unit is used to receive data from each optical detection unit, process the detection data of multiple nodes at the same time, calculate the concentration respectively, and select the appropriate node data as the final concentration calculation result according to the calculation results, thereby achieving the purpose of a single laser gas sensor covering an ultra-wide concentration detection range from 0.0001% to 100%.

[0035] In one embodiment of the present invention, in a multi-node gas chamber structure, since the first node has the shortest optical path and the shortest gas absorption time, the laser absorption rate of the first node is the lowest. The laser transmission distance of each node gradually increases, and the laser absorption rate gradually increases. The optical signal absorption diagram of each node is shown in FIG. Figure 2 shown.

[0036] In one embodiment of the present invention, the node optical detection unit is a linear detection unit, and its output voltage signal is linearly related to the laser power (mW). The splitting ratio of the node optical splitter can be designed according to actual needs. In general applications, the proportion of the light beam input to the optical detection unit is low, and the light beam with a high proportion is transmitted to the next node, which can prevent the light detection unit from being saturated and ensure that the subsequent node has a higher effective light signal, such as Figure 3 As shown, the laser emits light, which is split and reflected by five splitting nodes in the air chamber and finally input into the end light detector of the sixth node.

[0037] Each node's optical splitter is implemented using a coated spectrometer. By properly designing the spectrometer's angle, the optical path of the optical signal can be aligned within the air chamber. Assuming a 20% splitting ratio at each splitting node, 20% of the optical signal is input to the optical detector, and 80% of the signal is transmitted to the next node. Assuming negligible spectrometer loss, the power input to the optical detector at the first node is 20% of the initial power, the power input to the optical detector at the second node is 16% of the initial power, the power input to the optical detector at the third node is 12.80% of the initial power, the power input to the optical detector at the fourth node is 10.24% of the initial power, the power input to the optical detector at the fifth node is 8.19% of the initial power, and the power input to the optical detector at the sixth node is 32.76% of the initial power. By using only one laser light source and one air chamber structure, the spectrometer within the air chamber splits the laser into multiple beams, which are transmitted to the optical detection units at different nodes for detection. Multiple optical detection units are integrated into one sensor, thus achieving the goal of completing multiple sensor detection functions with just one device, reducing detection volume and cost.

[0038] In one embodiment of the present invention, the processor unit controls the laser die temperature, and the laser current is adjusted from I1 to I m Increase in steps, send periodically, adjust the amplification of each node, make the output voltage of each node within the detection range of the processor, and keep the amplitude of each node basically consistent, the laser current is from I1 to I m Step by step, the gas is s At each current step point I n Each node (node ​​number is represented by p) simultaneously collects the signal voltage value (V pn ), and finally obtain the voltage data group of each node related to the laser working current (I n ,V pn ), according to the valid data judgment conditions, the optimal group of valid data groups is selected for gas concentration calculation. When performing concentration calculation, each node data needs to be calibrated with the standard concentration and the calibration parameters are saved. The processor unit calls the corresponding calibration parameters to perform concentration calculation based on the finally selected node data to ensure that each node reports the gas concentration accurately within the valid data range. The processor unit makes a rationality judgment on each group of data based on data such as peak height and absorption peak width, and selects the optimal node data as the final concentration calculation data.

[0039] The optical detection unit uses a simple TIA structure for linear detection. By adjusting the transresistance of the TIA, the same node voltage range can be obtained. In this embodiment, a methane sensor is used as an example. The laser wavelength is 1653.7nm, the current adjustment range is 15mA to 50mA, the step is 0.05mA, a total of 700 test points, the gas chamber length is 2.5cm, and the optical path difference between each node is about 3cm. After inputting methane gas with a concentration of 2% (filled with nitrogen), the absorption curve of each node is as follows: Figure 4 shown.

[0040] Figure 4 In the example, node 1 has the shortest optical path and shows almost no absorption peak. The absorption peak of subsequent nodes gradually increases, and complete absorption occurs at node 6, where the absorption peak drops to 0V. The absorption rate of each node is different, and the concentration range that can be detected is also different. In this example, the optical path differences between multiple nodes are not much, and the detection ranges of adjacent nodes overlap significantly. To reduce cost and circuit complexity, only some nodes can be extracted for optical signal detection. The processor obtains multiple sets of data at the same time. Based on data such as peak height and absorption peak width, the rationality of each set of data is judged, and the optimal node data is selected as the final concentration calculation data. Since each node has a different detection range, each node will use a gas with a different concentration for concentration calibration and save the calibration parameters. The processor calls the corresponding calibration parameters based on the final selected node data for concentration calculation. In this example, when the methane concentration is higher than 20%, the data of node 1 can be selected for calculation. When the concentration is between 1% and 20%, nodes 2 and nodes 3 can be used for calculation. When the concentration is lower than 1%, nodes 5 and nodes 6 can be selected for calculation.

[0041] While the present invention has been generally described above, modifications and improvements are readily apparent to those skilled in the art. Therefore, modifications and improvements that do not depart from the spirit of the present invention are intended to be within the scope of the present invention.

Claims

1. A laser gas sensor module with an ultra-wide concentration detection range, characterized in that: Based on the TDLAS principle, it includes: A laser emitting unit, configured to emit tunable laser light; A multi-node air chamber structure includes at least one optical splitter and a segmented optical path, wherein the optical splitter splits the incident laser into two beams, one of which is transmitted to the optical signal detection unit, and the other continues to be transmitted along the optical path to the next optical splitting node; Multiple optical detection units are respectively arranged behind each splitting node to detect the optical signal of each node; The processor unit is used to receive data from each light detection unit, process multiple node detection data at the same time, perform concentration calculations respectively, and select appropriate node data as the final concentration calculation result according to the calculation results.

2. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The optical splitter can be realized by a coated optical splitter.

3. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The optical splitter may be realized by a prism structure.

4. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The node light detection unit is a linear detection unit, and its output voltage signal is in a linear relationship with the laser power.

5. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The splitting ratio of the node splitter can be designed according to actual needs. In general applications, the light beam input to the light detection unit has a low proportion, and the light beam with a high proportion is transmitted to the next node.

6. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: In the multi-node air chamber structure, the optical path of the first node is the shortest, and the laser transmission distance of each subsequent node gradually increases.

7. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The processor unit controls the laser tube core temperature, and the laser current is from I1 to I m Increase in steps and send periodically.

8. The ultra-wide concentration detection range laser gas sensor module according to claim 7, characterized in that: Adjust the amplification factor of each node so that the output voltage of each node is within the detection range of the processor and the amplitude of each node remains basically consistent.

9. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: When calculating the concentration of each node data, it is necessary to perform standard concentration calibration and save the calibration parameters. The processor unit calls the corresponding calibration parameters to perform concentration calculation based on the final selected node data.

10. The ultra-wide concentration detection range laser gas sensor module according to claim 1, characterized in that: The processor unit makes a rationality judgment on each set of data based on data such as peak height and absorption peak width, and selects the optimal node data as the final concentration calculation data.

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