CN110596327B - Method for detecting components and concentration of polluted gas - Google Patents
Method for detecting components and concentration of polluted gas Download PDFInfo
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- CN110596327B CN110596327B CN201911031792.8A CN201911031792A CN110596327B CN 110596327 B CN110596327 B CN 110596327B CN 201911031792 A CN201911031792 A CN 201911031792A CN 110596327 B CN110596327 B CN 110596327B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/27—Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0022—General constructional details of gas analysers, e.g. portable test equipment using a number of analysing channels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N2013/003—Diffusion; diffusivity between liquids
Abstract
The invention relates to a method for detecting components and concentration of a polluted gas, belongs to the technical field of gas concentration detection, and solves the problem that multiple gas components cannot be detected simultaneously in the prior art. The method comprises the following steps: arranging a multi-channel gas collection device, and arranging a single gas sensor in each channel; introducing polluted gas into a multi-channel gas collection device, determining component types of the polluted gas by using a single gas sensor of each channel, and obtaining an electric signal corresponding to the gas concentration of each component type; analyzing the electric signals, and determining the concentration of each component gas by combining the detection sensitivity calibrated in advance; for each component gas, the release speed of the pollution source to the gas is obtained according to the gas concentration of the gas and a gas turbulence diffusion model, and then detection results comprising all component types, the gas concentration of each component type and the release speed are output. The method has accurate, stable and reliable detection result and good expansibility.
Description
Technical Field
The invention relates to the technical field of gas concentration detection, in particular to a method for detecting components and concentration of polluted gas.
Background
Air composition monitoring is an important means of obtaining atmospheric quality in the context of global initiatives for ecology and environmental protection. The air composition monitoring system is utilized to obtain the concentration of the polluted gases in the air, such as CO, SO2, NO2 and the like, and the data are provided for departments of environment, weather and the like in real time, SO that powerful data support is provided for preventing atmospheric pollution and protecting ecology.
The polluted gas collecting device is used as an important part of an air composition monitoring system, and the data of the polluted gas collecting device directly relate to the evaluation of the air quality and the environment quality of a certain area. Therefore, the method has higher requirements on the accuracy, the real-time performance, the reliability and the like of the acquisition.
At present, the prior art mostly adopts special single gas acquisition device, acquires data through the sensor, transmits data to the server in real time, and the gaseous composition of pollution and concentration data in the server are obtained to long-range. When a plurality of gas components need to be collected, a plurality of types of gas collecting devices need to be equipped.
Disclosure of Invention
In view of the above analysis, the present invention provides a method for detecting the components and concentration of a polluted gas, so as to solve the problem that the prior art cannot detect multiple gas components simultaneously.
On one hand, the embodiment of the invention provides a method for detecting the components and the concentration of a polluted gas, which comprises the following steps:
arranging a multi-channel gas collection device, and arranging a single gas sensor in each channel;
introducing polluted gas into a multi-channel gas collection device, determining component types of the polluted gas by using a single gas sensor of each channel, and obtaining an electric signal corresponding to the gas concentration of each component type;
analyzing the electric signals, and determining the concentration of each component gas by combining the detection sensitivity calibrated in advance;
for each component gas, the release speed of the pollution source to the gas is obtained according to the gas concentration of the gas and a gas turbulence diffusion model, and then detection results comprising all component types, the gas concentration of each component type and the release speed are output.
The beneficial effects of the above technical scheme are as follows: through the multichannel gas collection equipment, all component types contained in the polluted gas can be detected simultaneously, and the gas concentration and the gas release speed of each component type are obtained. The used multi-channel gas acquisition equipment has the advantages of small volume, light weight, portability, and the like, and is suitable for various measuring environments. All the information of the polluted gas can be collected simultaneously by one multi-channel gas collecting device, so that the collecting efficiency of the method is obviously improved compared with the prior art.
Based on the further improvement of the method, the detection sensitivity is calibrated by the following steps:
introducing clean air without pollution gas into a certain channel of the multi-channel gas collecting equipment, and respectively collecting the initial voltage V of the main electrode and the auxiliary electrode at the output end of the single gas sensor in the channel after the clean air is stabilized 01 、V 02 ；
Controlling standard gas matched with the single gas sensor and with preset concentration C to be introduced into the channel, and respectively collecting current voltages V of a main electrode and an auxiliary electrode at the output end of the single gas sensor in the channel after the standard gas is stabilized 11 、V 12 ；
According to the initial voltage V 01 、V 02 And the present voltage V 11 、V 12 And obtaining the detection sensitivity S of the polluted gas concentration detection device to the standard gas component by combining the concentration C of the standard gas and a preset correction coefficient n.
The beneficial effects of the above further improved scheme are: aiming at the characteristic that the zero drift of a single gas sensor needs to be calibrated for multiple times, a novel method for calibrating the detection sensitivity is provided, the influence of environmental factors on the detection sensitivity can be effectively reduced, and the accuracy of acquired data is ensured.
Further, the detection sensitivity S of the contaminated gas concentration detection apparatus for the standard gas component is calculated by the following formula
S＝[(V 11 -V 01 )-n×(V 12 -V 02 )]/C。
The beneficial effects of the above further improved scheme are: the formula is an empirical formula summarized by a large number of tests of the inventor, the obtained detection sensitivity is high in accuracy, the actual requirement is met, and the design time and the cost can be effectively shortened by direct application.
Furthermore, when the detection sensitivity is calibrated, the environment with the same temperature, humidity and electromagnetic parameters as the actual test environment is adopted.
The beneficial effects of the above further improved scheme are: by adopting the environment with the same temperature, humidity and electromagnetic parameters as the actual test for calibration, the influence of environmental factors on the detection sensitivity in the actual test process can be effectively eliminated.
Further, the gas concentration of each component species is determined by:
acquiring an electric signal output by a single gas sensor of each channel of the multi-channel gas acquisition equipment;
respectively conditioning the electric signals to obtain the effective voltage V of the main electrode of the single gas sensor of each channel 1 ；
According to the effective voltage V of the main electrode 1 The concentration C' of the component gas is determined in accordance with the detection sensitivity S corresponding to the standard gas component.
The beneficial effects of the above further improved scheme are: through the signal conditioning circuit, the microampere level weak signal can be amplified into a visual analog signal in a preset range, and a digital signal reflecting the size of the analog signal is further obtained. After the influence of environmental factors on detection sensitivity in the actual test process is eliminated through calibration, the concentration of the component gas can be obtained only by collecting the main electrode voltage during actual use. The method is practical, simple and effective, and the accuracy of the detection result is high.
Further, the concentration C' of the component gas species is calculated by the following formula
The signal conditioning comprises filtering, amplifying and AD conversion.
The beneficial effects of the above further improved scheme are: the concentration C' of the component gas can be obtained by only collecting the main electrode voltage and through the calibrated detection sensitivity S, and the method is simple, high in detection result accuracy and strong in practicability.
Further, the gas turbulence diffusion model is
Wherein Q represents the gas release rate of a contaminant source to a component species, d represents the distance between a single gas sensor and the contaminant source, k represents the gas diffusion coefficient, v represents x Representing the component of the wind speed v on the line connecting the single gas sensor and the pollution source.
The beneficial effects of the above further improved scheme are: through a large number of experiments, the inventor summarizes a gas diffusion model for obtaining the release rate of a pollution source to a certain component type gas according to the concentration of the gas. The model has high detection result accuracy, and the direct application can shorten the design time and the design cost.
Further, the gas release rate of the pollution source for each of the component species is obtained by:
obtaining position coordinates (x, y, z) of each single gas sensor and position coordinates (x) of pollution source in multi-channel gas collection equipment 0 ,y 0 ,z 0 ) And further obtaining the distance d between each single gas sensor and the pollution source through the following formula
Obtaining the current wind speed v, and further obtaining the component v of the wind speed on the connecting line of each single gas sensor and the pollution source through the following formula x
v x ＝vcosα
In the formula, alpha represents the included angle between the wind speed and the connecting line of the single gas sensor and the pollution source;
the d, the v x And (4) carrying in a gas turbulence diffusion model to obtain the gas release speed Q of the pollution source to each component species.
The beneficial effects of the above further improved scheme are: the gas release speed of the pollution source to each component can be obtained according to the designed gas turbulence diffusion model, the method is simple, and a large number of tests prove that the accuracy of the detection result is high.
Further, when the detection sensitivity is calibrated, a main electrode and an auxiliary electrode at the output end of the single gas sensor are respectively connected with a signal conditioning circuit with the same structure, electric signals output by the main electrode and the auxiliary electrode are respectively subjected to the same filtering, amplification and AD conversion, and the conversion result is used as the initial voltage or the current voltage.
The beneficial effects of the above further improved scheme are: the signal conditioning circuit connected with the main electrode and the auxiliary electrode is arranged to have the same structure, and actually, the signal conditioning circuit is used for eliminating the influence of the circuit structure on the detection sensitivity, so that the influence caused by environmental factors such as temperature, humidity and electromagnetic interference is only needed to be further eliminated. A large number of tests prove that the detection result is accurate and the reliability is high.
Further, the method comprises the following steps:
and when the detection result is obviously wrong or the single gas sensor of each channel has no output signal, resetting the multi-channel gas acquisition equipment, then introducing the polluted gas again, and acquiring the electric signal again by the single gas sensor of each channel.
The beneficial effects of the above further improved scheme are: the system software is monitored in real time, and the accuracy and reliability of the acquired detection result are guaranteed. When the system is disturbed by strong static electricity, short-time interference and the like, the software program can be blocked and run away, and the system software can be operated again through the reset signal.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic view showing steps of a method for detecting the components and concentration of a contaminant gas according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram illustrating the components of an integrated multi-channel contaminant gas concentration detection apparatus according to embodiment 3 of the present invention;
FIG. 3 is a schematic diagram illustrating the components of an integrated multi-channel contaminant gas concentration detection apparatus according to embodiment 4 of the present invention;
FIG. 4 is a schematic diagram of the watchdog circuit connection according to embodiment 4 of the present invention;
FIG. 5 is a schematic diagram of the electrical connections of any one channel of the multi-channel gas collection device in accordance with embodiment 4 of the present invention.
Reference numerals:
r-resistance; c-capacitance; AGND-ground; v ce -a reference voltage; U1A, U2A, U2B, U3A, U3B, U4A, U4B — operational amplifiers, subscripts indicating the serial numbers.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
Example 1
One embodiment of the present invention discloses a method for detecting the components and concentration of a polluted gas, as shown in fig. 1, comprising the following steps.
S1, arranging multi-channel gas collection equipment, and arranging a single gas sensor in each channel;
s2, introducing polluted gas into the multi-channel gas collection equipment, determining component types of the polluted gas by the single gas sensor of each channel, and obtaining an electric signal corresponding to the gas concentration of each component type;
s3, analyzing the electric signals, and determining the concentration of each component type gas by combining the detection sensitivity calibrated in advance;
and S4, for each component type of gas, obtaining the release speed of a pollution source to the gas according to the gas concentration of the gas in combination with a gas turbulence diffusion model, and then outputting detection results including all the component types, the gas concentration of each component type and the release speed.
In practice, the polluted gas contains more than one amount of component species, such as CO, SO 2 、NO、NO 2 And the like. And the single gas sensor is used for determining one component in the polluted gas, converting the gas concentration information of the component into a corresponding electric signal through an electrochemical reaction and sending the corresponding electric signal to system processing software. The single gas sensor, such as CO gas, can be an existing CO-B4 sensor, SO 2 The gas can adopt the existing SO 2 The NO gas can adopt the existing NO/C-100 sensor, and NO 2 The gas can be the existing NO2-B43F sensor, and other existing gas sensors can also be used.
Compared with the prior art, the method provided by the embodiment can simultaneously detect all component species contained in the polluted gas through the multi-channel gas collection equipment, and obtain the gas concentration and the gas release speed of each component species. The used multi-channel gas acquisition equipment has the advantages of small volume, light weight, portability, and the like, and is suitable for various measuring environments. All the information of the polluted gas can be collected simultaneously by one multi-channel gas collecting device, so that the collecting efficiency of the method is obviously improved compared with the prior art.
Example 2
The improvement is carried out on the basis of the embodiment 1, and the factors influencing the accuracy of the acquisition result are mainly environmental factors such as temperature, humidity and electromagnetic interference. By designing the signal conditioning circuit with the same connection structure of the main electrode and the auxiliary electrode, the influence of the circuit structure on the detection sensitivity is practically eliminated. Further, the influence of environmental factors on the detection sensitivity can be eliminated by making a difference between the two outputs.
Preferably, the method adopts the following steps to calibrate the detection sensitivity:
s01, introducing clean air without pollution gas into a certain channel of the multi-channel gas collecting equipment, and respectively collecting single gas in the channel after stabilizationInitial voltage V of main electrode and auxiliary electrode at output end of sensor 01 、V 02 ；
S02, introducing standard gas matched with the single gas sensor and with preset concentration C into the channel, and respectively collecting current voltages V of a main electrode and an auxiliary electrode at the output end of the single gas sensor in the channel after the standard gas is stabilized 11 、V 12 ；
S03, according to the initial voltage V 01 、V 02 And the present voltage V 11 、V 12 And obtaining the detection sensitivity S of the polluted gas concentration detection device to the standard gas component by combining the concentration C of the standard gas and a preset correction coefficient n.
By repeating the above steps S01 to S03, the detection sensitivity S of the contaminated gas concentration detection apparatus for eliminating the influence of environmental factors on the standard gas of each component type can be obtained, and the gas concentration of each component type can be accurately evaluated.
Preferably, in step S03, the detection sensitivity S of the contaminated gas concentration detection apparatus for the standard gas component is calculated by the following formula
S＝[(V 11 -V 01 )-n×(V 12 -V 02 )]/C (1)
Preferably, the detection sensitivity is calibrated in steps S01 to S03 using the same environment as the actual test temperature, humidity and electromagnetic parameters. And connecting the single gas excitation end with an excitation circuit with the same structure and parameters, respectively connecting a main electrode and an auxiliary electrode of the output end of the single gas sensor with a signal conditioning circuit with the same structure, respectively performing the same filtering, amplifying and AD (analog-to-digital) conversion on electric signals output by the main electrode and the auxiliary electrode, and taking the conversion result as the initial voltage or the current voltage. The excitation circuit and the signal conditioning circuit can be manufactured into modules, and corresponding modules are directly replaced when the circuit is used, so that the manufacturing cost can be reduced.
Preferably, in step S3, the gas concentration of each component species is determined by:
s31, acquiring an electric signal output by a single gas sensor of each channel of the multi-channel gas acquisition equipment;
s32, respectively conditioning the electric signals to obtain the effective voltage V of the main electrode of the single gas sensor of each channel 1 ；
S33, according to the effective voltage V of the main electrode 1 The concentration C' of the component gas is determined in accordance with the detection sensitivity S corresponding to the standard gas component.
Preferably, in step S33, the concentration C' of the component species gas is calculated by the following formula
Preferably, the signal conditioning of step S32 includes filtering, amplifying, AD converting.
Preferably, the gas turbulent diffusion model is
Wherein Q represents the gas release rate of a contaminant source to a component species, d represents the distance between a single gas sensor and the contaminant source, k represents the gas diffusion coefficient, v represents x Representing the component of the wind speed v on the line connecting the single gas sensor and the pollution source.
Preferably, in step S4, the gas release rate of the pollution source for each component species is obtained by:
s41, obtaining position coordinates (x, y, z) of each single gas sensor and position coordinates (x) of pollution source in multi-channel gas collecting equipment 0 ,y 0 ,z 0 ) And further obtaining the distance d between each single gas sensor and the pollution source through the following formula
S42, acquiring the current wind speed v, and further acquiring the single wind speed v through the following formulaComponent v on the line connecting the gas sensor and the source of contamination x
v x ＝vcosα (5)
In the formula, alpha represents the included angle between the wind speed and the connecting line of the single gas sensor and the pollution source;
s43, converting the d and the v x And carrying in a gas turbulence diffusion model to obtain the gas release speed of the pollution source to each component species.
Preferably, the method for detecting the components and the concentration of the polluted gas further comprises the following steps:
and S5, when the detection result is obviously wrong or the single gas sensor of each channel has no output signal, resetting the multi-channel gas collecting equipment, then introducing the polluted gas again, and collecting the electric signal again by the single gas sensor of each channel.
Compared with the embodiment 1, the method provided by the embodiment is provided with the same main electrode and auxiliary electrode signal conditioning circuits, and the influence of environmental factors on the detection sensitivity is eliminated by the provided calibration method, so that the accurate gas concentration of each component of the polluted gas and the accurate release speed of the polluted gas to each component of the gas can be obtained. In addition, the method and the device provide real-time monitoring on the detection result and the output of the single gas sensor, and can automatically reset the multi-channel gas acquisition equipment to acquire data again when the detection result is obviously wrong or the single gas sensor of each channel has no output signal.
Example 3
The invention also provides an integrated multi-channel polluted gas concentration detection device using the method of embodiment 1, which comprises a multi-channel gas acquisition device and an ARM processor which are connected in sequence as shown in FIG. 2.
The multi-channel gas acquisition equipment is used for acquiring introduced polluted gas, determining the component types of the polluted gas and sending the electric signals corresponding to the gas concentration of each component type to the ARM processor. The contaminated gas contains one or more component species, such as CO, SO 2 、NO、NO 2 And the like.
And the ARM processor is used for analyzing the electric signals, determining the concentration of each component type gas by combining with the detection sensitivity calibrated in advance, further obtaining the release speed of a pollution source to each component type gas according to a gas turbulence diffusion model, and then outputting all the component types, the concentration of each component type gas and the release speed as detection results.
Example 4
The invention also provides an integrated multi-channel polluted gas concentration detection device of the method in the embodiment 2 by improving on the basis of the embodiment 3, as shown in fig. 3, different channels of the multi-channel gas collection equipment are in an isolated state; and all the channels have the same structure and size.
And each channel is provided with a single gas sensor which is used for determining a component in the polluted gas and converting the gas concentration information of the component into a corresponding electric signal through an electrochemical reaction and sending the electric signal to the ARM processor. A single gas sensor, for example, CO gas may be used with an existing CO-B4 sensor, SO 2 The gas can adopt the existing SO 2 The NO gas can be the existing NO/C-100 sensor, and NO is detected by the existing NO/C-100 sensor 2 The gas may be used with existing NO2-B43F sensors, as well as other existing gas sensors.
Preferably, each channel further comprises an excitation circuit connected to the input terminal of the single gas sensor, and a signal conditioning circuit respectively connected to the main electrode and the auxiliary electrode of the output terminal of the single gas sensor. The structure and parameters of the exciting circuit and the signal conditioning circuit of each channel are the same. The excitation circuit and the signal conditioning circuit can be manufactured into modules, and corresponding modules are directly replaced when the circuit is used, so that the manufacturing cost can be reduced.
The excitation circuit is used for providing stable starting voltage for the single gas sensor. As shown in FIG. 5, the driving circuit comprises an operational amplifier U2A, a resistor R2, a resistor R5, a resistor R6, a capacitor C1, a capacitor C6, a capacitor C7 and a 5V power supply. Wherein, the forward input end of the operational amplifier U2A is connected with a reference voltage V ce The reverse input end of the capacitor is connected with a resistor R6 and a capacitor C7The output end of the single sensor is connected with the output end of the single sensor, the power supply end of the single sensor is connected with a 5V power supply and is grounded through a capacitor C7, the output end of the single sensor is connected with the negative excitation end of the single sensor through a resistor R2, and is connected with the positive excitation end of the single sensor through a capacitor C7 and a resistor R5. And a capacitor C6 is connected between the positive excitation end and the negative excitation end of the single gas sensor. The reference voltage Vce is amplified by the operational amplifier of the operational amplifier U2A, and the loading capacity of the reference voltage Vce is improved. The filtering function can be realized through the capacitors C1, C6 and C7, and common power frequency interference is filtered.
And the signal conditioning circuit is used for filtering, amplifying and AD converting the electric signal output by the single gas sensor and sending the obtained processed signal to the ARM processor.
Preferably, the signal conditioning circuit includes a filtering and amplifying circuit and an AD converter connected in sequence. As shown in fig. 5, the filter amplifier circuit connected to the main electrode includes operational amplifiers U1A, U2B, U3A, resistors R1, R3, R4, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, capacitors C2, C3, C4, C5, C6, C8, and C9. Wherein, the main electrode is respectively connected with one end of a resistor R18 and the negative input end of an operational amplifier U2B through a resistor R17, and the other end of the resistor R18 is connected with a reference voltage V ce . The negative input end of the operational amplifier U2B is connected with the output end thereof through a parallel circuit of a resistor R3 and a capacitor C4, and the positive input end thereof is connected with a reference voltage V ce The output end of the operational amplifier is connected with the negative input end of the operational amplifier U1A, one end of the capacitor C2 and one end of the resistor R1 through a resistor R7. The other end of the capacitor C2 is connected with the output end of the operational amplifier U1A, and one end of the resistor R1 is connected with one end of the resistor R9. The positive input end of the operational amplifier U1A is respectively connected with one end of a resistor R14 and one end of a resistor R16, the other end of the resistor R16 is grounded, and the other end of the resistor R14 is respectively connected with a reference voltage V through a resistor R13 ce The operational amplifier U1A is connected with 5V voltage through a power supply end and is grounded through a capacitor C5. The other end of the resistor R12 and the other end of the capacitor C9 are respectively grounded. The other end of the resistor R11 is connected with the positive input end of the operational amplifier U3A for operationThe negative input end of the amplifier U3A is grounded via a resistor R8, and is connected with the output end via a resistor R4, and the output end outputs a main electrode voltage V via a resistor R10 1 And is grounded through a resistor R10 and a capacitor C8, and the power supply end of the operational amplifier U1AU3A is connected with 5V voltage and is grounded through a capacitor C3.
Three-stage amplification is realized through operational amplifiers U1A, U2B and U3A, and microampere level weak signals output by the main electrode and the auxiliary electrode are amplified into voltage analog signals of preset times. After the first stage of amplification, the operational amplifier U2B outputs a point 7 voltage U 1 Is composed of
u 1 ＝V ce -I×R 3 (6)
In the formula, V ce Representing a reference voltage, I representing a main electrode output current, R i The resistance value of the resistance Ri is shown.
After the second stage of amplification, the voltage u at the right end of the resistor R9 2 Is composed of
In the formula, V' is the voltage at the output point 1 of the operational amplifier U2A.
After the third stage of amplification (an in-phase proportional amplifying circuit consisting of an operational amplifier U3A), the final output V is 1 Is composed of
The in-phase proportional amplifying circuit has the following functions: the output current ranges of different types of gas sensors are different, so that the voltage signal ranges after the first two-stage amplification are different, and because the different types of sensors use the same AD converter and the AD conversion digits are limited, the second-stage output voltage u needs to be amplified in the same phase proportion 2 Is amplified to andthe acquisition range of the AD conversion circuit is close to the level, the acquisition resolution is improved, and the in-phase proportional amplification circuit can realize the acquisition; meanwhile, the in-phase proportional amplifying circuit has the characteristics of high input impedance and low output impedance, and the driving capability of output voltage can be increased. The signals amplified by the same phase proportion are voltages which can be identified by the AD conversion circuit, the AD conversion circuit is communicated with the ARM processor through the SPI data bus, and the ARM processor obtains voltages of the main electrode and the auxiliary electrode.
Preferably, the ARM processor performs the following steps of calibrating the detection sensitivity of the detection device corresponding to each of the polluted gases respectively:
SS1, controlling clean air without pollution gas to be introduced into one channel of the multi-channel gas collecting equipment, and respectively collecting initial voltages V of a main electrode and an auxiliary electrode of the channel after the clean air is stabilized 01 、V 02 ；
SS2, controlling standard gas matched with the single gas sensor in the channel and with preset concentration C to be introduced into the channel, and respectively collecting current voltages V of a main electrode and an auxiliary electrode of the channel after the standard gas is stabilized 11 、V 12 ；
SS3. according to the initial voltage V 01 、V 02 And the present voltage V 11 、V 12 And obtaining the detection sensitivity S of the polluted gas concentration detection device on the standard gas component by combining the concentration C of the standard gas and a preset correction coefficient n through the following formula
S＝[(V 11 -V 01 )-n×(V 12 -V 02 )]/C (10)
Through the steps SS 1-SS 3, the influence of environmental factors such as temperature, humidity and electromagnetic interference on the detection sensitivity can be eliminated.
Preferably, the ARM processor performs the following steps to determine the gas concentration of each component species:
SS4. reading main electrode voltage V output by each channel of the multi-channel gas collecting equipment after collecting the polluted gas 1 ；
SS5. according to the main electrode voltage V 1 In combination with the standard gasThe detection sensitivity S corresponding to the body component is determined by the following formula to determine the concentration C 'of the component gas'
Preferably, the gas turbulent diffusion model is
Wherein Q represents the gas release rate of a contaminant source to a component species, d represents the distance between a single gas sensor and the contaminant source, k represents the gas diffusion coefficient, v represents x Representing the component of the wind speed v on the line connecting the single gas sensor and the pollution source.
Preferably, the ARM processor performs the following steps to obtain the release rate of the pollution source to each component gas:
SS51, acquiring the position coordinates (x, y, z) of each single gas sensor and the position coordinates of the pollution source in the multi-channel gas acquisition equipment, and acquiring the distance d between each single gas sensor and the pollution source through the following formula
SS52, obtaining the current wind speed v, and further obtaining the component v of the wind speed on the connecting line of each single gas sensor and the pollution source through the following formula x
v x ＝vcosα (14)
In the formula, alpha represents the included angle between the wind speed and the connecting line of the single gas sensor and the pollution source;
SS53, the obtained distance d between each single gas sensor and the pollution source and the obtained component v of the wind speed on the connecting line of each single gas sensor and the pollution source x And carrying in a gas turbulence diffusion model to obtain the release speed Q of the pollution source to each component gas.
Preferably, the integrated multi-channel polluted gas concentration detection device further comprises a watchdog circuit and a data storage.
And the watchdog circuit is used for monitoring the state of the ARM processor, sending a reset signal to the ARM processor when detecting the fault of the ARM processor or the power supply undervoltage, controlling the ARM processor to restart and providing a manual reset function.
And the data storage is used for storing the detection sensitivity S of the polluted gas concentration detection device for each standard gas component, the obtained acquisition result and the specific acquisition time. When the device is used, the ARM processor automatically reads the detection sensitivity S, the obtained acquisition result and the specific acquisition time from the data storage period.
Preferably, as shown in fig. 4, the watchdog circuit comprises an SP706REN chip, a manual reset switch, a power supply; the WDI end, the RESET end and the PFO end of the SP706REN chip are respectively connected with the IO end I, the RESET end and the IO end II of the ARM processor, the WDO end of the SP706REN chip is connected with the WR end of the SP706REN chip and is grounded through the manual RESET switch, the VCC end and the GND of the SP706REN chip are respectively connected with the positive electrode and the negative electrode of the power supply, and the PFI end of the SP706REN chip is connected with the power supply voltage of the ARM processor.
Preferably, the output end of the ARM processor comprises an RS485 interface, an RS422 interface and the like, so that the multiple multi-channel polluted gas collecting devices can be conveniently expanded, and information intercommunication is realized.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (6)
1. A method for detecting the components and the concentration of polluted gas is characterized by comprising the following steps:
arranging a multi-channel gas collection device, and arranging a single gas sensor in each channel;
introducing polluted gas into a multi-channel gas collection device, determining component types of the polluted gas by using a single gas sensor of each channel, and obtaining an electric signal corresponding to the gas concentration of each component type;
analyzing the electric signals, and determining the concentration of each component gas by combining the detection sensitivity calibrated in advance;
for each component type gas, obtaining the release speed of a pollution source to the gas according to the gas concentration of the component type gas and a gas turbulence diffusion model, and then outputting a detection result comprising all component types, the gas concentration of each component type and the release speed;
calibrating the detection sensitivity by the following steps:
introducing clean air without pollution gas into a certain channel of the multi-channel gas collecting equipment, and respectively collecting the initial voltage V of the main electrode and the auxiliary electrode at the output end of the single gas sensor in the channel after the clean air is stabilized 01 、V 02 ；
Controlling standard gas matched with the single gas sensor and with preset concentration C to be introduced into the channel, and respectively collecting current voltages V of a main electrode and an auxiliary electrode at the output end of the single gas sensor in the channel after the standard gas is stabilized 11 、V 12 ；
According to the initial voltage V 01 、V 02 And the present voltage V 11 、V 12 Combining the concentration C of the standard gas and a preset correction coefficient n to obtain the detection sensitivity S of the polluted gas concentration detection device to the standard gas component, wherein the calculation formula is that S is [ (V) 11 -V 01 )-n×(V 12 -V 02 )]/C；
Determining the gas concentration of each component species by:
acquiring an electric signal output by a single gas sensor of each channel of the multi-channel gas acquisition equipment;
respectively conditioning the electric signals to obtain the effective voltage V of the main electrode of the single gas sensor of each channel 1 ；
According to the effective voltage V of the main electrode 1 Determining the concentration C' of the component gas by combining the detection sensitivity S corresponding to the standard gas component and calculating by the following formula
When the detection sensitivity is calibrated, a main electrode and an auxiliary electrode at the output end of a single gas sensor are respectively connected with a signal conditioning circuit with the same structure, electric signals output by the main electrode and the auxiliary electrode are respectively subjected to the same filtering, amplification and AD conversion, and the conversion result is used as the initial voltage or the current voltage; the influence of environmental factors on the detection sensitivity is eliminated by making a difference between the output voltages of the main electrode and the auxiliary electrode.
2. The method of claim 1, wherein the environment having the same temperature, humidity and electromagnetic parameters as the actual measurement is used for calibrating the detection sensitivity.
3. The method according to claim 2, wherein the detection of the concentration of the contaminant gas is performed by a gas sensor,
the signal conditioning comprises filtering, amplifying and AD conversion.
4. The method of claim 3, wherein the gas turbulence diffusion model is
Wherein Q represents the gas release rate of a pollutant source to a component speciesD denotes the distance of the single gas sensor from the contamination source, k denotes the gas diffusion coefficient, v x Representing the component of the wind speed v on the line connecting the single gas sensor and the pollution source.
5. The method according to claim 4, wherein the gas release rate of the pollution source for each component species is obtained by:
obtaining position coordinates (x, y, z) of each single gas sensor and position coordinates (x) of pollution source in multi-channel gas collection equipment 0 ,y 0 ,z 0 ) And further obtaining the distance d between each single gas sensor and the pollution source through the following formula
Obtaining the current wind speed v, and further obtaining the component v of the wind speed on the connecting line of each single gas sensor and the pollution source through the following formula x
v x ＝vcosα
In the formula, alpha represents an included angle between the wind speed and a connecting line of the single gas sensor and a pollution source;
the d, the v x And carrying in a gas turbulence diffusion model to obtain the gas release speed of the pollution source to each component species.
6. The method for detecting the composition and concentration of a contaminant gas according to claim 2, further comprising the steps of:
and when the detection result is obviously wrong or the single gas sensor of each channel has no output signal, resetting the multi-channel gas acquisition equipment, then introducing the polluted gas again, and acquiring the electric signal again by the single gas sensor of each channel.
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