An in-situ maintained dust concentration detection device and method using a non-powered light scattering method

Abstract

The present invention relates to an in-situ maintained dust concentration detection device and method using a non-powered light scattering method, and belongs to the technical field of dust concentration detection. The device includes a metal housing, an insulating carrier, a laser, a photodiode and a light trap, a filter, a light shield and a signal processing board; the filter is installed at the bottom of the photodiode; the light shield is connected to the insulating carrier and installed at the outer end of the light scattering area, and can be removed at any time to facilitate cleaning of dust particles on the surface of the laser and the filter. The detection device calculates the dust concentration value by combining the short-time difference typing data processing algorithm in the digital signal processing unit of the single-chip microcomputer. The calculation method can remove the interference of natural light and achieve accurate characterization of the dust concentration. The structure of the present invention has the advantages of easy maintenance, openness, and non-power, and can achieve accurate detection of dust concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of dust concentration detection, and relates to an in-situ maintained dust concentration detection device and method using a non-powered light scattering method. Background Art

[0002] Dust is one of the major disasters in the industrial environment. The large amount of dust generated during the industrial production process can easily cause dust explosions and pneumoconiosis. Therefore, it is particularly important to strengthen the real-time online and accurate detection of dust concentration at the work site. Industrial production dust has harsh conditions such as a large particle size range, high concentration, and high humidity, making it very difficult for dust concentration sensors to accurately detect for a long time. This is also the current research focus and hot spot.

[0003] At present, sensors for online detection of productive dust concentration mainly use the light scattering method, but there are problems such as blockage of dust extraction pipelines and pollution of detection units and lasers. Due to the use of a closed darkroom structure, sensor maintenance is difficult and the process is complicated. All current optical dust concentration sensor structures have the disadvantages of frequent and difficult maintenance, making it difficult for light scattering dust concentration sensors to accurately and effectively detect dust on site. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an in-situ maintained unpowered light scattering method dust concentration detection device and method, which completely changes the current problems of light scattering method dust concentration sensors being easy to clog, easy to pollute, and difficult to maintain, so that the structure of the present invention has the advantages of easy maintenance, openness, and unpoweredness, thereby achieving accurate detection of dust concentration.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] Solution 1: An in-situ maintained non-powered light scattering method dust concentration detection device 11, comprising a metal housing 2, an insulating carrier 6, a laser 9, a photodiode 4, a light trap 7, a filter 5, a light shield 8 and a signal processing board 3;

[0007] The laser 9, photodiode 4, light trap 7 and signal processing board 3 are mounted on an insulating carrier 6, and a metal housing 2 is mounted on the outside to protect and shield external interference;

[0008] The filter 5 is mounted at the bottom of the photodiode 4;

[0009] The light shield 8 is connected to the insulating carrier 6 and installed at the outer end of the light scattering area. It can be removed at any time to facilitate cleaning of dust particles on the surface of the laser 9 and the filter 5; the light scattering area is the dust detection area, that is, the area between the laser 9 and the photodiode 4.

[0010] Furthermore, the light shield 8 and the insulating carrier 6 are connected to each other by magnet adsorption.

[0011] Furthermore, the light shield 8 is provided with strip-shaped ventilation holes, and under the action of external wind flow, dust particles can enter the light scattering area through the ventilation holes.

[0012] Furthermore, the device also includes a display unit, a communication unit, a power supply circuit and an audible and visual alarm.

[0013] Furthermore, the signal processing board 3 includes an IV conversion circuit, a voltage amplification circuit and an AD conversion circuit which are connected in sequence; the input end of the IV conversion circuit is connected to a photodiode 4 .

[0014] Solution 2: An in-situ maintained unpowered light scattering dust concentration sensor, comprising the unpowered dust concentration detection device 11 in Solution 1, a single-chip digital signal processing unit 12, a display unit 13, a communication unit, a power supply circuit and an audible and visual alarm 15;

[0015] The single-chip digital signal processing unit 12 is connected to the signal processing board 3 through a signal wire 1, and is used to perform short-time difference typing data processing algorithm calculation on the signal collected by the unpowered dust concentration detection device 11, and finally obtain the dust concentration value;

[0016] The display unit 13, the communication unit, and the sound and light alarm 15 are respectively connected to the single-chip digital signal processing unit 12; the display unit 13 is used to display the dust concentration value; the communication unit is installed in the sensor housing 14, and is used to transmit the dust concentration value calculated by the single-chip digital signal processing unit 12 to the management system or the mobile terminal; when it is detected that the dust concentration exceeds the preset threshold, the sound and light alarm 15 alarms;

[0017] The power supply circuit supplies power to each unit device requiring power supply.

[0018] Further, the single-chip microcomputer digital signal processing unit 12 uses a short-time difference type data processing algorithm to perform calculations, specifically including the following steps:

[0019] 1) Design a pulse circuit to output high and low levels, and a pulse laser 9 driving circuit with a period of 1k; when the level is low, the laser 9 is turned off, and the signal output by the photodiode 4 is the dark current signal of the photodiode and the external natural light interference signal, and the tested value is used as the zero point value; when the pulse signal is high, the laser 9 generates dark current, external natural light interference and the scattered light intensity of dust particles; after completing 1s of data sampling, two 512 data arrays a1 and a2 are formed accordingly;

[0020] 2) Process the data to form an array a with a data volume of 512, that is, a=a2-a1;

[0021] 3) Rearrange the data in array a from small to large;

[0022] 4) Calculate the number M based on the external input data, take M / 2 data above and below the median data in array a, and calculate the average value of the M data as x;

[0023] 5) According to the set calibration coefficient k, the dust concentration value c=k*x is calculated. After the recording, display and communication functions are completed, the next round of sampling calculation is entered.

[0024] Further, in step 5), the specific setting method of the calibration coefficient k is:

[0025] The beneficial effects of the present invention are:

[0026] (1) In terms of structure, the present invention removes the fan and exhaust pipe of the current light scattering dust concentration detection unit, thus avoiding the problem of the pipe being blocked by dust. Then, the detection unit in the darkroom is made into an open detection unit, so that dust particles can diffuse freely into the detection area. The open detection structure facilitates the cleaning of dust adsorbed on the surface of the photodiode and the laser, and the maintenance process is simple and convenient. However, the open detection structure is prone to interference from external natural light. On the one hand, a narrow bandwidth filter is installed at the bottom of the photodiode, and on the other hand, a light shield with strip-shaped ventilation holes is installed at the outer end of the open detection unit to prevent interference from external light sources without hindering the free diffusion of dust particles. The light shield and the detection unit are connected by magnet adsorption. Without any tools, the light shield can be easily removed to remove the dust adsorbed on the laser and the photodiode, and the maintenance process is simple and convenient.

[0027] (2) In order to eliminate the influence of natural light on the detection results, the sensor of the present invention is designed with an automatic zero point detection function and a signal processing algorithm with a non-fixed zero point, which eliminates the interference of external natural light and ensures the detection accuracy and stability, thereby realizing accurate detection of dust concentration.

[0028] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0030] Figure 1This is a structural diagram of the dust concentration detection device using the unpowered light scattering method of the present invention;

[0031] Figure 2 It is a front schematic diagram of the dust concentration sensor using the unpowered light scattering method of the present invention;

[0032] Figure 3 for Figure 2 The right side cross-sectional view of

[0033] Figure 4 It is a schematic diagram of the back side of the dust concentration sensor using the unpowered light scattering method of the present invention;

[0034] Figure 5 It is a signal control relationship diagram of the dust concentration sensor using the unpowered light scattering method of the present invention;

[0035] Figure 6 is a circuit diagram of the signal processing board in Example 1;

[0036] Figure 7 It is a three-dimensional schematic diagram of the light shield in Example 2;

[0037] Figure 8 A schematic diagram of the specific dimensions of the light shield in Example 2;

[0038] Fig. 9 This is a data processing flow chart of the dust concentration sensor using the unpowered light scattering method of the present invention;

[0039] Fig.10 It is the curve relationship between the initial value of the sensor and the dust concentration;

[0040] Fig.11 This is the calibration fitting curve diagram of the sensor.

[0041] Figure markings: 1-signal wire, 2-metal shell, 3-signal processing board, 4-photodiode, 5-filter, 6-insulating carrier, 7-light trap, 8-light shield, 9-laser, 10-laser wire, 11-unpowered dust concentration detection device, 12-single-chip microcomputer digital signal processing unit, 13-display unit, 14-sensor housing, 15-sound and light alarm, 16-nameplate one, 17-nameplate two, 18-hanging rod, 19-hanging bracket, 20-safety plate, 21-aviation plug, 22-rear cover fixing screw. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, 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 invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0043] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0044] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0045] See also Figure 1 to Figure 7 The present invention provides an in-situ maintained non-powered light scattering dust concentration detection device 11, such as Figure 1As shown, it mainly includes a photodiode 4, a filter 5, a laser 9, a light trap 7, a light shield 8, a signal processing board 3, an insulating carrier 6 and a metal shell 2. In order to avoid interference from external light, a light shield 8 is installed at the outer end of the light scattering area. The light shield 8 can be removed at any time to clean the adsorbed dust on the surface of the laser 9 and the photodiode 4. There are strip vents on the light shield 8. Under the action of external wind flow, dust particles can enter the light scattering area through the vents. The laser 9, the photodiode 4, the light trap 7, and the signal processing board 3 are installed on the insulating carrier 6, and a metal shell 2 is installed on the outside to protect and shield external interference. The photodiode 4, the laser 9, and the signal processing board 3 are installed on the insulating carrier 6, and the light trap 7 is installed. In order to reduce the interference of external natural light, a 904nm filter 5 is installed at the bottom of the photodiode 4, and a light shield 8 is installed in the detection area. The light shield 8 has a vent hole with a length of 20mm and a width of 3mm. On the one hand, it is convenient for dust to diffuse to the detection area with the wind flow, and on the other hand, it can reduce the interference of external natural light. The light shield 8 and the insulating carrier 6 are connected to each other by magnet adsorption, which is convenient for the light shield 8 to be easily removed, and the dust particles adsorbed on the surface of the filter 5 and the laser 9 are cleaned. A metal shell 2 (stainless steel outer cover) is installed at the outer end of the insulating carrier 6, forming a dust concentration detection device 11 of the non-powered light scattering method, and together with the single-chip digital signal processing unit 12, the display unit 13, the communication unit, the power supply circuit, the sound and light alarm 15 and other parts, constitute a dust concentration sensor of the non-powered light scattering method.

[0046] like Figure 5 As shown, the single-chip digital signal processing unit 12 is connected to the signal processing board 3 through the signal wire 1, which is used to calculate the signal collected by the unpowered dust concentration detection device 11 by the short-time difference typing data processing algorithm, and finally obtain the dust concentration value; the display unit 13, the communication unit, and the sound and light alarm 15 are respectively connected to the single-chip digital signal processing unit 12; the display unit 13 is used to display the dust concentration value. The communication unit is installed in the sensor housing 14, and is used to transmit the dust concentration value calculated by the single-chip digital signal processing unit 12 to the management system or the mobile terminal; when the dust concentration is detected to exceed the preset threshold, the sound and light alarm 15 alarms. The power supply circuit supplies power to each unit device that needs power supply.

[0047] Example 1: Figure 6 As shown, the signal processing board 3 includes an IV conversion circuit, a voltage amplification circuit and an AD conversion circuit which are connected in sequence; the input end of the IV conversion circuit is connected to the photodiode 4.

[0048] Embodiment 2: As a preferred embodiment, Figure 7-Figure 8As shown, the specific structural dimensions of the light shield 8 are: L=43mm, L1=7mm, L2=3mm, W=22mm, W1=4mm, W2=3mm, W3=3mm, and R3=1mm.

[0049] Embodiment 3: The single-chip microcomputer digital signal processing unit 12 uses a short-time difference type data processing algorithm to perform calculations, such as Fig. 9 As shown, the specific calculation process is:

[0050] (1) Design a pulse circuit with a high level of 5V and a low level of 0V, and a pulse laser driving circuit with a period of 1k. When the level is low, the laser 9 is turned off, and the signal output by the photodiode 4 is the dark current signal of the photodiode and the external natural light interference signal. The tested value is used as the zero point value. When the pulse signal is high, the laser 9 generates dark current, external natural light interference, and the scattered light intensity of dust particles. After completing 1s of data sampling, two arrays of 512 data are formed, a1 and a2.

[0051] (2) The data is processed, a=a2-a1, forming an array a with a data volume of 512, and the data in array a is rearranged again, from small to large.

[0052] (3) Calculate the number M based on the external input data, select M / 2 data above and below the median data in array a, and calculate the average value of the M data as x.

[0053] (4) According to the set calibration coefficient k (using low-concentration quadratic polynomial curve fitting and high-concentration linear fitting to achieve accurate calibration of the dust concentration sensor using the unpowered light scattering method), the dust concentration value c = k*x is calculated. After the recording, display, and communication functions are completed, the next round of sampling calculation is entered.

[0054] Verification experiment:

[0055] In order to verify the test effect of the dust concentration sensor using the unpowered light scattering method, the dust sensor calibration system of the State Key Laboratory of Gas Disaster Monitoring and Emergency Technology of Chongqing Research Institute of China Coal Technology and Engineering Group was used, which mainly includes a continuous dust generator, a wind tunnel, a dust collector, an exhaust fan, a gas sampler, a DC regulated power supply, and a dust concentration sensor using the unpowered light scattering method. The dust uses 80-mesh dry coal powder. The continuous dust generator sprays the coal powder evenly and continuously into the wind tunnel. Under the action of the stable airflow in the wind tunnel, the coal powder is evenly distributed in the wind tunnel. In order to reduce the interference of the sensor to be tested on the dust flow field in the wind tunnel, only the dust concentration detection unit using the unpowered light scattering method is placed in the wind tunnel, and the main control board of the sensor is placed outside the wind tunnel. The sampling DC regulated power supply is powered with a voltage of 24V, and the detection value of the sensor is displayed on the main control board. The sampler collects the mixture of coal dust and gas in the wind tunnel, and obtains the accurate dust concentration value in the wind tunnel by weighing and calculation, which is used as the standard reference value. The sampler and the unpowered dust concentration sensor work simultaneously, and the detection value of the unpowered dust concentration sensor and the standard dust concentration value collected and weighed and calculated by the sampler are recorded in real time for further analysis and verification.

[0056] 1. Sensor detection value calibration

[0057] By adjusting the dust emission of the dust generator and changing the distribution concentration of dust in the wind tunnel, the initial value of the dust concentration sensor using the unpowered light scattering method under different dust concentration conditions (hereinafter referred to as the sensor initial value) is obtained, namely: Fig.10 The x value in the data processing flow, the relationship between the actual dust concentration and the initial value of the sensor is as follows: Figure 8 shown.

[0058] according to Fig.10 From the data curve, it can be seen that the initial value of the dust concentration sensor of the unpowered light scattering method has a good positive correlation with the actual dust concentration, and the overall data distribution has good linearity. 3 When the sensor outputs a value of 880, it is caused by the local noise of the sensor. After removing the local noise, the sensor detection value is calibrated to achieve accurate representation of dust concentration. Figure 8 The distribution pattern of detection points, the dust concentration is less than 120mg / m 3 When the detection point linearity is poor, a quadratic polynomial fitting is used; when the dust concentration is higher than 120 mg / m 3 When the detection point distribution has a high linearity, linear fitting is used, and the fitting curve and the error calculation after fitting are as follows: Fig.11 As shown (where Fig.11 (a) is the fitting curve of the low concentration dust sensor. Fig.11 (b) is the calibration fitting curve of the high-concentration dust sensor, the dust concentration is 120 mg / m 3The initial value of the corresponding sensor is 1070, and after removing the zero point value 880, it is 190. Then the value of the sensor after removing the zero point is calibrated in sections with 190 as the boundary, as shown in the following formula.

[0059]

[0060] Where x = x0-z, y is the sensor's detection value of dust concentration; x0 is the initial value of the sensor; z is the dust concentration of 0 mg / m 3 The sensor zero point value, through testing z = 880; x is the value of the sensor after removing the zero point.

[0061] according to Fig.11 The calibration fitting curve of the dust concentration sensor using the unpowered light scattering method shows that the quadratic polynomial fitting at low concentration and the linear fitting at high concentration both have good fitting effects, with R-square values ​​greater than 0.99. The fitting values ​​have low errors from the detected values, with errors less than ±15%.

[0062] 2. Sensor detection accuracy test analysis

[0063] In order to test the detection accuracy of the unpowered dust concentration sensor of the present invention, the unpowered dust concentration sensor is placed in the wind tunnel according to the above-mentioned test system, the detection results of the sensor are recorded and compared with the standard dust concentration value obtained by sampling and weighing by the sampler, and the test error of the unpowered light scattering dust concentration sensor is calculated, as shown in Table 1.

[0064] Table 1 Statistics of detection accuracy of dust concentration sensor using unpowered light scattering method

[0065]

[0066] According to the data statistics in Table 1, the detection accuracy of the dust concentration sensor of the non-powered light scattering method of the present invention meets the standard requirements, which is less than 15%. When the dust concentration is relatively low, the detection error is relatively high, and the value is greater than 10%. The main reason is that the dust detected by the non-powered light scattering method dust concentration sensor is freely diffused to the detection area, which is relatively small in dust quantity, relatively weak in test signal, and difficult in signal processing compared to the powered light scattering method dust concentration sensor, resulting in a large test error, but its error can still meet the standard requirements. When the dust concentration is high, the detection accuracy of the non-powered light scattering method dust concentration sensor is high, and the test error is less than 10%, which has a good detection effect and meets the requirements of the "MT / T1102-2009 Dust Concentration Sensor for Coal Mines" standard.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. An in-situ maintained unpowered light scattering dust concentration sensor, comprising an unpowered dust concentration detection device (11), wherein the unpowered dust concentration detection device (11) comprises a metal housing (2), an insulating carrier (6), a laser (9), a photodiode (4) and a light trap (7), characterized in that: The unpowered dust concentration detection device (11) further comprises a filter (5), a light shield (8) and a signal processing board (3); the sensor further comprises a single-chip digital signal processing unit (12); The laser (9), photodiode (4), light trap (7) and signal processing board (3) are mounted on an insulating carrier (6), and a metal housing (2) is mounted on the outside to protect and shield external interference; The filter (5) is mounted on the bottom end of the photodiode (4); The light shield (8) is connected to the insulating carrier (6), installed at the outer end of the light scattering area, and can be removed at any time to facilitate cleaning of dust particles on the surface of the laser (9) and the filter (5); the light scattering area is a dust detection area, that is, the area between the laser (9) and the photodiode (4); The single-chip digital signal processing unit (12) is connected to the signal processing board (3) via a signal wire (1) and is used to perform short-time difference type data processing algorithm calculation on the signal collected by the unpowered dust concentration detection device (11) to finally obtain a dust concentration value; The single-chip microcomputer digital signal processing unit (12) uses a short-time difference type data processing algorithm to perform calculations, specifically comprising the following steps: 1) Design a pulse circuit to output high level and low level, and a pulse laser (9) driving circuit with a period of 1k; when the pulse circuit is at a low level, the laser (9) is turned off, and the signal output by the photodiode (4) is the dark current signal of the photodiode and the external natural light interference signal, and the tested value is used as the zero point value; when the pulse signal is at a high level, the laser (9) is turned on, and the signal output by the photodiode (4) is the dark current signal of the photodiode, the external natural light interference and the scattered light intensity of the dust particles; after completing 1s of data sampling, two arrays a1 and a2 are formed accordingly; 2) Process the data to form an array a, i.e., a=a2-a1; 3) Rearrange the data in array a from small to large; 4) Calculate the number M based on the external input data, take M / 2 data above and below the median data in array a, and calculate the average value of the M data as x; 5) According to the set calibration coefficient k, calculate the dust concentration value c = k * x. After the recording, display and communication functions are completed, enter the next round of sampling calculation; The specific setting method of the calibration coefficient k is:

2. The dust concentration sensor using the unpowered light scattering method according to claim 1, characterized in that: The light shield (8) and the insulating carrier (6) are connected to each other by means of magnetic adsorption.

3. The dust concentration sensor using the unpowered light scattering method according to claim 1, characterized in that: The light shield (8) is provided with ventilation holes, and under the action of external wind flow, dust particles can enter the light scattering area through the ventilation holes.

4. The dust concentration sensor using the unpowered light scattering method according to claim 1, characterized in that: The signal processing board (3) comprises an IV conversion circuit, a voltage amplification circuit and an AD conversion circuit which are connected in sequence; the input end of the IV conversion circuit is connected to a photodiode (4).

5. The dust concentration sensor using the unpowered light scattering method according to any one of claims 1 to 4, characterized in that: The sensor also includes a display unit (13), a communication unit, a power supply circuit and an audible and visual alarm (15); The display unit (13), the communication unit, and the sound and light alarm (15) are respectively connected to the single-chip digital signal processing unit (12); the display unit (13) is used to display the dust concentration value; the communication unit is installed in the sensor housing (14) and is used to transmit the dust concentration value calculated by the single-chip digital signal processing unit (12) to the management system or the mobile terminal; when it is detected that the dust concentration exceeds a preset threshold value, the sound and light alarm (15) sounds an alarm; The power supply circuit supplies power to each unit device requiring power supply.

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