Calibration system for metering capacity of mass concentration of particulate matter

Abstract

The embodiment of the utility model provides a calibration system for the metering capacity of the mass concentration of particulate matters. The calibration system comprises an aerosol generating and blending device (100) and a mass concentration standard device (200), the aerosol generating and blending device (100) comprises a particulate matter generating device (2) and an aerosol generator (1) connected to the particulate matter generating device (2), the aerosol generator (1) is provided with at least two aerosol outlets (10), the mass concentration standard device (200) comprises a cutter and a microbalance, the cutter can be connected to the microbalance through a pipeline, the microbalance is provided with a mass sensor, and the mass sensor is connected to the aerosol generator (1) through a pipeline. The mass concentration standard device (200) is an oscillating balance method particulate matter measuring instrument, the first aerosol outlet is connected with a cutter of the mass concentration standard device (200), and the second aerosol outlet is connected with a particulate matter sampling port of the calibrated particulate matter measuring instrument. And the calibration precision of the metering capability of the mass concentration of the calibrated particulate matter measuring instrument is improved.

Description

Technical Field

[0001] The utility model relates to the field of calibration of the metrological ability of mass concentration, and particularly relates to a calibration system for the metrological ability of the mass concentration of particulate matter. Background Art

[0002] PM 2.5 / PM 10 They are respectively called fine particulate matter and inhalable particulate matter. PM 2.5 refers to particulate matter with an aerodynamic equivalent diameter less than or equal to 2.5 μm in the atmosphere, also known as respirable particulate matter. PM 2.5 has a small particle size, is rich in a large amount of toxic and harmful substances, has a long residence time in the atmosphere, and a long transportation distance, thus having a greater impact on human health and the quality of the atmospheric environment. Fine particulate matter with a particle size below 2.5 μm is not easily blocked. After being inhaled into the human body, it will directly enter the bronchi, interfering with the gas exchange in the lungs and causing diseases including asthma, bronchitis, and cardiovascular diseases. Currently, PM 2.5 particulate matter is the primary pollutant in the air in China. Monitoring and effective treatment of PM 2.5 are the goals of the environmental protection departments and the national government in China.

[0003] PM 2.5 measuring instruments are used for the collection and mass concentration measurement of PM 2.5 particulate matter, and have the functions of particulate matter screening, collection, and / or measurement. Due to different principles of the instruments and different calibration methods used before leaving the factory, the response curves and accuracies of the instruments vary greatly, resulting in a large difference in the measured mass concentration in the same environment, and poor data comparability when the instruments are applied, which brings inconvenience to users.

[0004] In order to ensure the accuracy of the measurement data of particulate matter mass concentration measuring instruments such as PM 2.5 measuring instruments, it is necessary to calibrate the particulate matter mass concentration monitoring instruments. Utility Model Content

[0005] The embodiment of the utility model provides a calibration system for the metrological ability of the mass concentration of particulate matter, which can solve the technical problem of "in order to ensure the accuracy of the measurement data of measuring instruments such as particulate matter mass concentration measuring instruments, it is necessary to calibrate the particulate matter mass concentration monitoring instruments" existing in the prior art.

[0006] To achieve the above object, an embodiment of the present utility model provides a calibration system for the metrological ability of the mass concentration of particulate matter, including an aerosol generation and mixing device and a mass concentration standard device; the aerosol generation and mixing device includes: a particulate matter generation device and an aerosol generator connected to the particulate matter generation device, the aerosol generator having at least two aerosol outlets: a first aerosol outlet and a second aerosol outlet, the mass concentration standard device includes a cutter and a microbalance, the cutter can be connected to the microbalance through a pipeline, and the microbalance has a mass sensor;

[0007] The mass concentration standard device is an oscillating microbalance particulate matter measuring instrument;

[0008] The first aerosol outlet is connected to the cutter of the mass concentration standard device;

[0009] The second aerosol outlet is connected to the particulate matter sampling port of the particulate matter measuring instrument to be calibrated.

[0010] The above technical solution has the following beneficial effects: An aerosol generation and mixing device is adopted to generate particulate matter and further mix the generated particulate matter into aerosol, providing a uniform, stable and aerosol environment with adjustable concentration within a certain concentration range for the calibration of the particulate matter mass measuring instrument. The oscillating microbalance technology is used as the standard device to determine the first mass of the separated particulate matter according to the frequency change of the particulate matter, and calculate the standard concentration value according to the first mass. For the particulate matter measuring instrument to be calibrated, the particulate matter in the aerosol is also separated to obtain the second mass of the particulate matter, and the measured value of the particulate matter measuring instrument to be calibrated is calculated according to the second mass. Based on the standard concentration value and the measured value of the particulate matter measuring instrument to be calibrated, the mass concentration indication error is calculated, and the uncertainty of the mass concentration indication error is calculated. According to the uncertainty of the mass concentration indication error, it is judged whether the metrological ability of the mass concentration of the particulate matter measuring instrument to be calibrated is accurate. The calibration accuracy of the metrological ability of the mass concentration of the particulate matter measuring instrument to be calibrated is greatly improved. Description of the Drawings

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0012] Figure 1 It is a flowchart of a calibration method for the metrological ability of the mass concentration of particulate matter according to an embodiment of the present utility model;

[0013] Figure 2It is the logic structure diagram of a calibration system for the measurement ability of the mass concentration of particulate matter in an embodiment of the present utility model;

[0014] Figure 3 It is the measurement principle diagram of the particulate matter measuring instrument to be calibrated in an embodiment of the present utility model;

[0015] Figure 4 It is the schematic diagram of the principle of the mass concentration standard device in an embodiment of the present utility model;

[0016] Figure 5 It is the schematic diagram of the aerosol shunt step of the mass concentration standard device in an embodiment of the present utility model;

[0017] Figure 6 It is the schematic diagram of the principle of the aerosol generation and mixing device in an embodiment of the present utility model;

[0018] Figure 7 It is the calibration schematic diagram in an embodiment of the present utility model.

[0019] The reference numerals are shown as:

[0020] 1. Aerosol generator; 2. Particulate matter generation device; 3. Diffusion section; 4. Aerosol mixing chamber; 9. Electrostatic neutralization device; 10. Aerosol outlet; 100. Aerosol generation and mixing device; 200. Mass concentration standard device; 5. Collection section; 6. Bottom bracket; 7. Dust collector pipeline; 8. Main circulation pipeline. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0022] Such as Figure 1As shown in the figure, in combination with the embodiments of the present invention, a calibration method for the metrological ability of the mass concentration of particulate matter is provided. Using a calibration system for the metrological ability of the mass concentration of particulate matter, the metrological ability of the mass concentration of particulate matter of a particulate matter measuring instrument is calibrated. The calibration system for the metrological ability of the mass concentration of particulate matter includes: an aerosol generation and mixing device 100 and a mass concentration standard device 200; the aerosol generation and mixing device 100 includes: a particulate matter generation device 2 and an aerosol generator 1 connected to the particulate matter generation device 2. The aerosol generator 1 has at least two aerosol outlets 10: a first aerosol outlet and a second aerosol outlet. The mass concentration standard device 200 includes a cutter and a microbalance. The cutter can be connected to the microbalance through a pipeline. The microbalance has a mass sensor;

[0023] The mass concentration standard device 200 is an oscillating microbalance particulate matter measuring instrument;

[0024] The first aerosol outlet is connected to the cutter of the mass concentration standard device 200;

[0025] The second aerosol outlet is connected to the particulate matter sampling port of the particulate matter measuring instrument to be calibrated;

[0026] The calibration method for the metrological ability of the mass concentration of particulate matter described above includes:

[0027] Generate particulate matter with a preset diameter through the particulate matter generation device 2;

[0028] Generate a uniform and stable aerosol with a preset concentration range from the particulate matter with a preset diameter through the aerosol generator 1;

[0029] S101: Send an aerosol with a first preset volume and a preset concentration range into the cutter of the mass concentration standard device 200. Separate the particulate matter with a preset diameter through the cutter. The separated particulate matter accumulates on the microbalance of the mass concentration standard device 200. Record the frequency change of the particulate matter accumulated on the microbalance through the mass sensor. Determine the first mass of the separated particulate matter according to the frequency change of the particulate matter, and calculate the standard concentration value according to the first mass;

[0030] At the same time, send a gas with a second preset volume and the same preset concentration range into the particulate matter sampling port of the particulate matter measuring instrument to be calibrated. Separate the particulate matter with a preset diameter, and determine the second mass of the separated particulate matter. Calculate the measured value of the particulate matter measuring instrument to be calibrated according to the second mass. The first preset volume is equal to the second preset volume;

[0031] S103: Calculate based on the standard concentration value and the measured value of the particulate matter measuring instrument to be calibrated to obtain the mass concentration indication error;

[0032] S104: Calculate the uncertainty of the indication error of the mass concentration, and determine whether the metrological ability of the mass concentration of the calibrated particulate matter measuring instrument is accurate according to the uncertainty of the indication error of the mass concentration.

[0033] Preferably, the preset concentration range includes: a first concentration range, a second concentration range or a third concentration range, and the first concentration range, the second concentration range or the third concentration range increases in sequence;

[0034] Within 1 hour, the average mass concentration change of the aerosol generated in the aerosol generator 1 does not exceed 4%, and the absolute value of the mass concentration difference of the aerosol between any two aerosol outlets 10 is not greater than 4.9%.

[0035] Preferably, when the aerosol generation and mixing device 100 generates aerosol, the method for restricting the particle size range of the generated aerosol includes:

[0036] Select aerosol sources with different diameters to generate particulate matter that meets the preset diameter requirements, or

[0037] When the diameter of the particulate matter cannot meet the preset diameter requirements, use an external particulate matter cutting device to screen the generated particulate matter by particle size and screen out the particulate matter that meets the preset diameter requirements.

[0038] Preferably, the mass concentration standard device 200 includes a first cutter and a second cutter. A first diverter is connected after the first cutter, and the first outlet of the first diverter can be connected to a first microbalance through a pipeline;

[0039] The second outlet of the first diverter is connected to the second cutter through a pipeline, and the second cutter can be connected to a second microbalance through a pipeline; wherein, the first diameter of the particulate matter cut by the first cutter is greater than the second diameter of the particulate matter cut by the second cutter;

[0040] The calibration method for the metrological ability of the mass concentration of the said particulate matter further includes:

[0041] When there is only one calibrated particulate matter measuring instrument and the diameter of the particulate matter that the calibrated particulate matter measuring instrument can monitor is the first diameter, send a first preset volume of aerosol in the preset concentration range into the first cutter of the mass concentration standard device 200, separate the particulate matter with the first diameter through the first cutter, pass through the first outlet of the first diverter, and finally accumulate on the first microbalance;

[0042] When there is only one particulate matter measuring instrument to be calibrated and the diameter of the particulate matter that the calibrated particulate matter measuring instrument can monitor is the second diameter, an aerosol with a preset concentration range in a first preset volume is sent into the first cutter of the mass concentration standard device 200. The particulate matter with the first diameter is separated by the first cutter, passes through the first outlet of the first shunt, and the remaining particulate matter passes through the second outlet of the first shunt. The particulate matter with the second diameter is separated by the second shunt and finally accumulates on the second microbalance.

[0043] When there are two particulate matter measuring instruments to be calibrated, and the diameter of the particulate matter that the first calibrated particulate matter measuring instrument can monitor is the first diameter, and the diameter of the particulate matter that the second calibrated particulate matter measuring instrument can monitor is the second diameter, an aerosol with a preset concentration range in a first preset volume is sent into the first cutter of the mass concentration standard device 200. The particulate matter with the first diameter is separated by the first cutter, passes through the first outlet of the first shunt, and finally accumulates on the first microbalance. The remaining particulate matter passes through the second outlet of the first shunt. The particulate matter with the second diameter is separated by the second shunt and finally accumulates on the second microbalance.

[0044] Preferably, the mass concentration range that the mass concentration standard device 200 can measure is 20 - 1000 μg / m 3 。

[0045] Preferably, the mass concentration indication error is expressed as:

[0046]

[0047] where, Δc—the mass concentration indication error;

[0048] c s —the arithmetic mean of the standard concentration values of the mass concentration standard device 200, μg / m 3 ;

[0049] c m -the arithmetic mean of the concentration measurement values of the calibrated particulate matter measuring instrument, μg / m 3 。

[0050] Preferably, the sources of the uncertainty of the mass concentration indication error include: the uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument and the uncertainty component introduced by the mass concentration standard value. The uncertainty of the mass concentration indication error is expressed as:

[0051]

[0052] where, u r (c m) represents the uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument;

[0053] u r (c s ) represents the uncertainty component introduced by the standard value of the mass concentration.

[0054] Preferably, the uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument is introduced by the measurement repeatability of the calibrated particulate matter measuring instrument and the reading resolution of the calibrated particulate matter measuring instrument. The uncertainty component introduced by the standard value of the mass concentration includes: the uncertainty component introduced by the mass concentration standard device 200 and the uncertainty component introduced by the non-uniformity of the aerosol generation and mixing device 100;

[0055] The calibrated particulate matter measuring instrument continuously calculates the n corresponding measurement values of the calibrated particulate matter measuring instrument. The uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument is expressed as:

[0056]

[0057] where s n-1 represents the measurement repeatability,

[0058] u t (c m ) represents the uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument;

[0059] The uncertainty introduced by the mass concentration standard device 200 is:

[0060] u r1 (c s )

[0061] The uncertainty introduced by the non-uniformity of the aerosol generation and mixing device 100 is:

[0062] u r2 (c m )

[0063] The uncertainty introduced by the standard value of the mass concentration is obtained:

[0064]

[0065] The uncertainty of the mass concentration indication error is calculated:

[0066]

[0067] Preferably, the calibration method for the metrological ability of the mass concentration of the particulate matter further includes:

[0068] The uncertainty of the indication error of the mass concentration is corrected by a correction factor k greater than 1 to obtain the expanded uncertainty:

[0069] U(Δc) = k·u(Δc) (11).

[0070] Preferably, the calibration method for the metrological capacity of the mass concentration of the particulate matter further includes:

[0071] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated, turn on the particulate matter measuring instrument to be calibrated and perform sampling, read the flow indication values shown on the flow standard device and the flow indication values of the particulate matter measuring instrument to be calibrated 3 times respectively, and calculate the flow indication error according to formula (1):

[0072]

[0073] where: ΔQ represents the flow indication error;

[0074] represents the arithmetic mean of the flow indication values of the particulate matter measuring instrument to be calibrated, L / min;

[0075] represents the arithmetic mean of the measured indication values of the flow standard device, L / min;

[0076] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated, turn on the particulate matter measuring instrument to be calibrated and perform sampling, read the measured indication values 3 times, and calculate the average flow deviation according to formula (2):

[0077]

[0078] where: ΔQ R represents the average flow deviation;

[0079] represents the arithmetic mean of the measured indication values of the flow standard device, L / min;

[0080] Q s represents the working point flow of the particulate matter measuring instrument to be calibrated, L / min;

[0081] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated, turn on the particulate matter measuring instrument to be calibrated and perform sampling, read the flow indication values of the particulate matter measuring instrument to be calibrated, repeat the measurement 6 times, and calculate the flow repeatability according to formula (3):

[0082]

[0083] In the formula, s r represents the flow repeatability;

[0084] Q R,i represents the measurement result of the i-th time, L / min;

[0085] represents the arithmetic mean of the flow indication values of the calibrated particulate matter measuring instrument, L / min;

[0086] n represents the number of measurements.

[0087] Measure the initial flow value Q of the calibrated particulate matter measuring instrument using a flow standard device, and start timing. Thereafter, read the flow value once every 20 minutes for a total of 3 times. When the single pumping cycle is less than 1 hour, the interval time can be shortened so as to read 3 flow indication values within a single pumping cycle. Calculate the sampling flow stability according to the formula (4) by taking the maximum and minimum values among the 4 flow indication values:

[0088]

[0089] where, ΔQ represents the flow stability;

[0090] Q max represents the maximum flow indication value of the calibrated particulate matter measuring instrument, L / min;

[0091] Q min represents the minimum flow indication value of the calibrated particulate matter measuring instrument, L / min;

[0092] Q represents the initial flow value of the calibrated particulate matter measuring instrument, L / min;

[0093] During the normal operation of the calibrated particulate matter measuring instrument, read and record the time displayed by the calibrated particulate matter measuring instrument as the start time t0, and at the same time start the stopwatch to time. When it runs for 1 hour, read and record the display time t1 of the calibrated particulate matter measuring instrument and the display time t2 of the stopwatch respectively. Calculate the timing indication error according to the formula (5):

[0094] Δt = t1 - t0 - t2 (5)

[0095] where, Δt represents the timing indication error, s;

[0096] t0 represents the start time of the calibrated particulate matter measuring instrument, h - m - s;

[0097] t1 represents the end time of the calibrated particulate matter measuring instrument, h - m - s;

[0098] t2 represents the display time of the stopwatch, h - m - s.

[0099] Place a standard thermometer at the same height beside the temperature sensor of the particulate matter measuring instrument to be calibrated. After the reading of the standard thermometer stabilizes, read and record the temperature indication value T of the standard thermometer respectively. s and the displayed temperature indication value T of the particulate matter measuring instrument to be calibrated. m Calculate the temperature indication error according to formula (6):

[0100] ΔT = T m - T s (6)

[0101] where, ΔT represents the temperature indication error, °C;

[0102] T m represents the displayed temperature indication value of the particulate matter measuring instrument to be calibrated, °C;

[0103] T s represents the temperature indication value of the standard thermometer, °C;

[0104] Place it at the same height beside the pressure sensor of the particulate matter measuring instrument to be calibrated, and read and record the pressure indication value p of the standard barometer and the pressure indication value p displayed by the particulate matter measuring instrument to be calibrated respectively. s and the pressure indication value p displayed by the particulate matter measuring instrument to be calibrated. m Calculate the atmospheric pressure indication error of the particulate matter measuring instrument to be calibrated according to formula (7):

[0105] Δp = p m - p s (7)

[0106] where, Δp represents the atmospheric pressure indication error, kPa;

[0107] p m represents the pressure indication value of the particulate matter measuring instrument to be calibrated, kPa;

[0108] p s represents the pressure indication value of the standard barometer, kPa.

[0109] As Figure 1 shown, in combination with the embodiments of the present invention, a calibration system for the metrological ability of the mass concentration of particulate matter is also provided, including: an aerosol generation and mixing device 100 and a mass concentration standard device 200; the aerosol generation and mixing device 100 includes: a particulate matter generation device 2 and an aerosol generator 1 connected to the particulate matter generation device 2. The aerosol generator 1 has at least two aerosol outlets 10: a first aerosol outlet and a second aerosol outlet. The mass concentration standard device 200 includes a cutter and a microbalance. The cutter can be connected to the microbalance through a pipeline. The microbalance has a mass sensor.

[0110] The mass concentration standard device 200 is an oscillating microbalance particulate matter measuring instrument.

[0111] The first aerosol outlet is connected to the cutter of the mass concentration standard device 200;

[0112] The second aerosol outlet is connected to the particulate matter sampling port of the calibrated particulate matter measuring instrument;

[0113] Preferably, the mass concentration standard device 200 includes a first cutter and a second cutter. After the first cutter, a first diverter is connected. The first outlet of the first diverter can be connected to a first microbalance through a pipeline; The cutter includes a first cutter and a second cutter. The first cutter and the second cutter can be used simultaneously or one of them can be selected for use;

[0114] The second outlet of the first diverter is connected to the second cutter through a pipeline, and the second cutter can be connected to a second microbalance through a pipeline; wherein, the first diameter of the particulate matter cut by the first cutter is greater than the second diameter of the particulate matter cut by the second cutter.

[0115] Preferably, the mass concentration standard device 200 further includes a first dryer disposed after the first diverter and before the first microbalance. The first dryer can be connected to the first diverter and the first microbalance respectively through pipelines;

[0116] The mass concentration standard device 200 further includes a second dryer disposed after the second diverter and before the second microbalance. The second dryer can be connected to the second diverter and the second microbalance respectively through pipelines.

[0117] Preferably, the aerosol generation and mixing device 100 further includes an electrostatic neutralization device 9 that can be connected to the particulate matter generation device 2. The electrostatic neutralization device 9 is used to remove static electricity from the particulate matter generated by the particulate matter generation device 2.

[0118] Preferably, the aerosol generation and mixing device 100 further includes a particulate matter cutting device. One end of the particulate matter cutting device is connected to the particulate matter generation device 2 through a pipeline, and the other end of the particulate matter cutting device is connected to the electrostatic neutralization device 9 through a pipeline. The particulate matter cutting device is used to screen the generated particulate matter by particle size when the diameter of the particulate matter does not meet the preset diameter requirement, and screen out the particulate matter that meets the preset diameter requirement.

[0119] Preferably, the aerosol generation and mixing device 100 further includes an aerosol mixing chamber 4. The aerosol mixing chamber 4 can be connected to the particulate matter generation device 2 and the aerosol generator 1 respectively through pipelines. The aerosol mixing chamber has a diffusion section 3 at the upper part. The diffusion section 3 is a honeycomb structure with pores and is used to mix the aerosol.

[0120] Preferably, the particulate matter generation device 2 is a wet aerosol generator or a dry generation device.

[0121] The beneficial technical effects obtained by the embodiments of the present utility model are as follows:

[0122] An aerosol generation and mixing device is adopted to generate particulate matter and further mix the particulate matter to generate aerosol, providing a uniform, stable and aerosol environment with adjustable concentration within a certain concentration range for the calibration of the particulate matter mass measuring instrument. The oscillating microbalance technology is used as the standard device. According to the frequency change of the particulate matter, the first mass of the separated particulate matter is determined, and the standard concentration value is calculated based on the first mass. For the calibrated particulate matter measuring instrument, the particulate matter in the aerosol is also separated to obtain the second mass of the particulate matter, and the measured value of the calibrated particulate matter measuring instrument is calculated based on the second mass. Based on the calculation of the standard concentration value and the measured value of the calibrated particulate matter measuring instrument, the mass concentration indication error is obtained, and the uncertainty of the mass concentration indication error is calculated. According to the uncertainty of the mass concentration indication error, it is judged whether the metrological ability of the mass concentration of the calibrated particulate matter measuring instrument is accurate. The calibration accuracy of the metrological ability of the mass concentration of the calibrated particulate matter measuring instrument is greatly improved. The above technical solutions of the embodiments of the present utility model will be described in detail below in combination with specific application examples. For technical details not introduced during the implementation process, reference can be made to the relevant descriptions in the previous text.

[0123] PM 2.5 The mass concentration measuring instrument generally consists of a sample collection unit (including a sampling port, PM 2.5 cutter and sampling tube, etc.), a sample measurement unit, a data processing unit and a display unit. Its working principle is as follows: The ambient air sample is extracted at a constant flow rate. The sample collection unit cuts and separates the particulate matter and transports it to the sample measurement unit. The sample measurement unit measures the PM 2.5 particulate matter sample. The data processing unit analyzes and calculates the measurement result, and finally the measurement result is output by the display unit. The working principle is shown in Figure 3 as shown.

[0124] Currently, the instruments used for measuring the concentration of PM 2.5 particulate matter in ambient air all use a cutter to screen PM 2.5 particulate matter, use a filter membrane (tape) for sampling, and measure the mass of the collected particulate matter by the direct weighing method, the oscillating balance method or the beta-ray attenuation method, as shown in Table 1.

[0125] Table 1 PM 2.5 Concentration monitoring method

[0126]

[0127] It can be seen that the filter membrane weighing method is for PM 2.5The most direct method for measuring mass concentration, with a simple measurement model and a clear traceability chain for mass and volume measurements, is recognized internationally as the reference method for PM 2.5 monitoring. However, due to its principle limitations, the gravimetric method cannot continuously, real-time, and online monitor PM 2.5 . It is difficult to meet the requirements of air quality monitoring in the environmental protection field. Therefore, at present, environmental protection departments at home and abroad widely use sampling and monitoring instruments based on the oscillating microbalance method and the beta-ray method to monitor PM 2.5 in real time.

[0128] Since the sampling methods and measurement models of the oscillating microbalance method and the beta-ray method are different from those of the filter weighing method, in order to ensure the consistency and accuracy of measurement results, it is necessary to study the traceability of the above-mentioned principle sampling and measurement instruments and conduct verification and calibration on this basis. Since the gravimetric method, the oscillating microbalance method, and the beta-ray method all rely on a cutter to separate the particulate matter with an aerodynamic equivalent diameter less than or equal to 2.5 μm in atmospheric particulate matter, collect it on a filter membrane or filter tape, and then conduct measurement and analysis. Therefore, the accuracy of the particulate matter measuring instrument, including PM 2.5 , the metrological performance of the cutter and the sampling component directly affects the accuracy of the PM 2.5 monitoring results. Therefore, the value traceability (i.e., calibration) of the PM 2.5 measuring instrument includes two major parts: the cutting characteristic detection of the cutter for PM 2.5 , and the verification and calibration of the measurement component for PM 2.5 .

[0129] The method for improving the metrological ability of ambient air particulate matter mass concentration can improve the calibration service ability of the PM 2.5 \PM 10 mass concentration monitor, aiming to improve the metrological traceability ability of ambient air particulate matter such as PM 2.5 . By using a rapid particulate matter mass concentration measuring instrument and an aerosol generation and mixing device, the uncertainty level of the oscillating microbalance method particulate matter measuring instrument is confirmed, and the stability and uniformity of the aerosol generation and mixing device used to generate PM 2.5 , PM 10 are clarified.

[0130] Among them, the oscillating microbalance method PM 2.5 / PM 10 particulate matter measuring instrument based on dual-channel sampling and measurement is used as a particulate matter mass concentration measuring standard instrument, with a measurement range of 20 - 1000 μg / m 3 , and a standard uncertainty of 4.5%, which is better than 5%, meeting the technical requirements for the standard PM 2.5 mass concentration measuring instrument in JJF1659 - 2017.

[0131] An aerosol generation and mixing device is used for aerosol generation and mixing, providing a uniform, stable, and aerosol environment with adjustable concentration within a certain concentration range for the calibration of particulate matter mass measuring instruments. The aerosol concentration ranges from 10 μg / m 3 to 1000 μg / m 3 . The average concentration change of the generated particulate matter at the center point and other places within 1 hour does not exceed 4%, that is, the stability does not exceed 4%. There are 4 aerosol outlets 10, and the absolute value of the difference in aerosol mass concentration between any two aerosol outlets 10 is not greater than 4.9%. It can simultaneously meet the calibration requirements of environmental air particulate matter mass concentration testers such as PM 10 , PM 2.5 , etc., and low-concentration dust meters. The principle is shown in Figure 7 . It is used for the calibration of portable PM 2.5 measuring instruments and PM 10 measuring instruments installed at fixed locations.

[0132] I. Oscillating balance method particulate matter measuring instrument

[0133] In the embodiment of the present utility model, an oscillating balance method PM 2.5 / PM 10 particulate matter measuring instrument based on dual-channel sampling measurement is used as a calibration device, which has a dual gas path and can simultaneously measure the PM 10 and PM 2.5 particulate matter mass concentration. The principle is as shown in Figure 4 . Its measurement range is 20 - 1000 μg / m 3 , and the standard uncertainty is 4.5%, which is better than 5%, meeting the technical requirements for standard PM 2.5 mass concentration measuring instruments in JJF1659 - 2017. Using the oscillating microbalance technology, it can be equivalent to the manual weighing method for measuring suspended particulate matter in the ambient air. It can be widely used in environmental air monitoring, indoor air quality monitoring, and human health exposure research. The specific parameters are shown in Table 2.

[0134] The oscillating balance method particulate matter monitor includes: a particulate matter cutter, a mass monitoring unit based on the oscillating balance principle, a control unit, a data acquisition and signal processing unit, a sobbing power system, and an auxiliary unit that cooperates with the system to work effectively; the main auxiliary units include a dryer, a shunt, a cooler, a filter, a heater, a flow monitoring and control, temperature and pressure detection components, etc.

[0135] It also includes: a sampling pump. The particulate matter cutting and shunting part is connected to the mass detection part. The mass detection part is connected to the sampling pump through one of the flow detection and control parts, and the particulate matter cutting and shunting part is also directly connected to the sampling pump through the remaining flow detection and control parts. It can achieve automatic monitoring and accurate detection of the concentration of particulate matter in the atmosphere, and at the same time can achieve the effect of low cost.

[0136] Full Chinese operation interface, built-in large-capacity memory; real button operation, touch screen can be added; data is displayed in real time, such as frequency and concentration curves; data can be stored for more than 5 years. Mobile storage devices can be selected. Data transmission devices can be configured to achieve wired or wireless, short-distance or long-distance, real-time data transmission or remote diagnosis. Automatic screen saver design, electromagnetic compatibility design, expandable design. Wide power supply design, adapting to 85–264VAC, 50 / 60Hz power supply (excluding pump); temperature, flow rate, data storage method, etc. can be set, and the standard temperature can be set according to different national conditions; meteorological five parameters (module) can be expanded; multiple analog inputs, DA outputs and alarm outputs.

[0137] Among them, the particulate matter cutter is used to collect the particulate matter cutting and shunting of the gas; the flow rate monitoring and control is used to determine the mass detection of the particulate matter quality and concentration collected; the control unit has at least two channels to control the flow rate detection and control of the sampling gas flow rate.

[0138] The principle is: air of a known volume passes through a sampling head (PM 10 , PM 2.5 ) with a cut-off diameter for separation. The separated particulate matter accumulates on a microbalance. The microbalance has a mass sensor, and the microbalance performs mass detection on the particulate matter. The mass is manifested by the change in frequency. After calculation with the sampling volume, the mass concentration is obtained.

[0139] Table 2 Technical Parameters

[0140]

[0141]

[0142] As Figure 5 shown, the dual-channel structure design (i.e., it can measure PM 10 and PM 2.5 ) at the same time. The airflow (16.67L / min) after the PM 10 cutter first passes through the splitter 1 and is divided into two paths. One path of PM 10 directly passes through a stainless steel main gas pipeline and is connected to the inlet of the 1st sampling unit. One path of PM 2.5 needs to pass through the splitter 2 again and is divided into a main flow rate of PM 2.5 (1.67L / min) and an auxiliary flow rate of (13.3L / min). PM 2.5The main flow is connected to the inlet of the 2-way sampling unit through another stainless steel main gas pipeline, while the auxiliary flow is directly connected to the inlet end of the primary filter behind the control unit backplane. Finally, these three flows all pass through the flow sensors and their respective control valves (stabilized within the deviation range of the set flow rate) and reach the air extraction pump.

[0143] PM 10 and PM 2.5 The main flows of both PM

[0144] II. Aerosol generation and mixing device

[0145] By calibrating the measuring instrument, the accuracy and consistency of the measurement results of the measuring instrument can be ensured. The most intuitive and effective calibration method is to provide an aerosol mixing chamber 4 with a sufficiently uniform and adjustable particulate matter concentration. The measuring instrument to be tested and the reference standard device simultaneously collect the same volume of aerosol from the test chamber, measure them separately, and then evaluate and utilize the difference between the two.

[0146] An aerosol generation and mixing device is adopted for aerosol generation and mixing, providing a uniform, stable, and concentration-adjustable aerosol environment within a certain concentration range for the calibration of particulate matter mass measuring instruments. The aerosol concentration ranges from 10 μg / m 3 to 1000 μg / m 3 . The average concentration change of the generated particulate matter at the center point, etc. within 1 h does not exceed 4%, that is, the stability does not exceed 4%. There are 4 aerosol outlets 10, and the absolute value of the difference in aerosol mass concentration between any two aerosol outlets 10 is not greater than 4.9%, which can simultaneously meet the calibration requirements of environmental air particulate matter mass concentration testers such as PM 10 and PM 2.5 , as well as low-concentration dust meters. It is used for the calibration of portable PM 2.5 measuring instruments and PM 10 measuring instruments installed at fixed locations.

[0147] (I) Principle structure of the aerosol generation and mixing device

[0148] The aerosol generation and mixing device mainly consists of several functional modules such as aerosol generation, electrostatic neutralization, particulate matter screening, mixing, power pump, and communication control. The design schematic diagram and test point distribution diagram of the aerosol generation and mixing device are as shown in Figure 6As shown in the figure. The working principle of the aerosol generation and mixing device is that the standard dust is diffused by the aerosol generator 1, and after passing through the cutter and the electrostatic neutralizer, it enters the aerosol mixing chamber 4, where the dust forms a stable particle concentration field. The pipeline flow of the control system is adjusted by the fan, the flowmeter and the frequency converter, and the aerosol concentration in the chamber can be adjusted by supplementing air. The uniformity of the gas and particles at low flow rates is fully considered. The upper part of the aerosol mixing chamber 4 has a diffusion section 3, and the lower part has a collection section 5. The aerosol mixing chamber 4 is supported by a bottom bracket 6. The diffusion section 3 has a honeycomb structure with a certain aperture, which plays a certain role in improving the air flow pattern and the uniformity of the aerosol at low flow rates. The fan sends air to the aerosol generator through the dust collector pipeline 7 and the main circulation pipeline 8.

[0149] Selectively limit the particle size range of the generated aerosol from two aspects. 1: Select different aerosol sources to generate aerosol particles with the required particle size; 2: If the particle size range of the aerosol source is not appropriate, an external particle cutting device can be connected to screen the particle size of the aerosol. Different particle size particle cutters can be selected according to the aerosol particle size range.

[0150] A sampling point is set at about 1 / 3 of the bottom of the mixing section. Multiple sampling points can be set. To ensure the consistency and stability of the sampling concentration, single-point sampling can be selected at the center point, or multiple-point sampling can be set at symmetric positions. Comparison is carried out by means of isokinetic sampling or directly putting the measuring instrument to be tested (if the volume is small enough) into the chamber.

[0151] (2) Key components

[0152] Ensure the stable and reliable operation of the generation and mixing device through the key components corresponding to dust generation, electrostatic neutralization, aerosol particle size limitation, and pump flow.

[0153] (1) Dust generation

[0154] The dust generation concentration of the generation and mixing device is concentrated in 20 μg / m 3 ~10 mg / m 3 , and the range span of the mass concentration is large. Therefore, both dry and wet generation devices are used to achieve high-precision control in the entire range. A portable wet aerosol generator 1 based on the aerosol spraying principle is mainly used to achieve low-concentration aerosol generation, and to achieve uniform and stable aerosol in the concentration range of 20 μg / m 3 ~1 mg / m 3 . High-concentration aerosol generation can be achieved through the dry generation device, and uniform and stable aerosol can be achieved in the concentration range below 10 mg / m 3 .

[0155] (2) Electrostatic neutralization

[0156] The static electricity neutralization device 9 mainly ensures that during the aerosol generation process, static electricity is neutralized to prevent static agglomeration and remove particle static electricity. The flow parameters that the static electricity neutralization device 9 needs to control should meet the flow requirements of the device. The selected volumetric flow for static electricity neutralization is 1 - 15 m 3 / h.

[0157] (3) Aerosol particle size limitation

[0158] In order to maintain the uniformity of the aerosol in the aerosol mixing chamber 4, it is necessary to limit the large particles in the dust generation. Therefore, a particle size screening device is added to the aerosol channel. Due to the limitation of the air flow rate, a cyclone PM 10 separator is selected to preliminarily screen the aerosol entering the aerosol mixing chamber 4 to obtain particulate matter with particle sizes meeting the requirements. Among them, according to the requirements of parameters such as the volume of the chamber, particulate matter concentration and uniformity, and sampling flow rate, the air volume is controlled.

[0159] (4) Pump flow

[0160] The flow is jointly controlled by a frequency converter and a fan. The frequency converter is used to control and adjust the speed of a three-phase AC asynchronous motor. It has stable performance, rich combination functions, high-performance vector control technology, low-speed high-torque output, good dynamic characteristics, and strong overload capacity. When the frequency converter drives the fan to start, it reduces the impact of the starting current on the power grid, reduces reactive power, can adjust the flow within the required range to meet the application requirements, and is also relatively convenient for installation and maintenance with high reliability.

[0161] (3) Implementation methods of main technical indicators

[0162] For different aerosol concentrations, select a suitable aerosol generator 1. In the mixing chamber, the particulate matter can be selected according to A1 and A2 in ISO 12103-1, and different types of particulate matter can be generated according to different needs. The sampling points at the center point and the reference points (including 4 sampling inlets) are connected to an external sampler using smooth inner wall stainless steel pipelines. The four-way sampling pipeline design maintains the same and symmetrical structure, which can ensure the stability and reliability of the aerosol concentration.

[0163] During the verification of the aerosol concentration and the parameters at the center point and the reference points (including 4 sampling inlets) in the aerosol chamber, a high-precision particulate matter measuring instrument is used for traceability.

[0164] (4) Aerosol generation and mixing device uniformity and stability test plan and data analysis

[0165] The calibration process of particulate matter mass concentration monitoring instruments mainly uses the instrument to be calibrated and a standard device for sampling comparison. Therefore, during the testing process, it is necessary to ensure the uniformity of samples between sampling points first.

[0166] The uniformity and stability of the aerosol generation and mixing device directly affect the calibration results of the measuring instrument. Therefore, the mass concentration change at the center point of the generation and mixing device within 1 h was measured; since the aerosol generation and mixing device may carry multiple measuring instruments to be tested for comparison and measurement simultaneously, the deviation between 4 test ports was tested to meet different requirements.

[0167] During the testing process of stability and uniformity, the optical measurement method based on the light scattering principle was used to measure the particulate matter mass concentration, which is rapid in reacting to the change trend of particulate matter, and the calibrated measuring instrument will measure more reliably.

[0168] The testing methods include: 1. Parameter testing of the aerosol generation and mixing device. The parameters of the device include the concentration, uniformity and stability of the generated aerosol. The testing should take into account real-time performance and measurement accuracy, involving the number of test points, test stations, test time and test methods, etc.; 2. Calibration and testing using this aerosol generation and mixing device: Test the concentration and dispersion of particulate matter in the aerosol. Four instruments are sampled simultaneously, and the consistency of instrument sampling should be fully considered. The involved contents include sampling position, sampling components, sampling stability, sampling method and quality control during the sampling process, etc.

[0169] 1) 1h stability test

[0170] After the particulate matter generation is stable, the change trend of the particulate matter concentration in the generation and mixing device within 1 h is represented by the stability at a single point (center point). Particulate matter with concentrations of 0.1 mg / m 3 、0.3 mg / m 3 、0.8 mg / m 3 、1.5 mg / m 3 was generated respectively, and a high-precision measuring instrument was used for single-point stability detection. For each concentration of particulate matter, 1 set of tests was conducted every 4 minutes for a total of 1 h, and each set was measured 2 times, with a total of 16 sets of tests. The standard deviation was calculated as the stability; the maximum value of the standard deviation among the 4 concentrations was used as the average concentration change of the particulate matter within 1 h, and the stability was better than 4%. The experimental results are shown in Table 3 below;

[0171] Table 3 Data table of stability test of fine particulate matter generator

[0172] (a)

[0173]

[0174] (b)

[0175]

[0176] 2) Deviation experiment between 4 test points:

[0177] In order to calibrate and compare multiple instruments, 4 symmetric points are selected as test points during the generation process of particulate matter. The test points are numbered 1 to 4, and particulate matter with concentrations of 0.2 mg / m 3 , 0.4 mg / m 3 , 0.8 mg / m 3 and 1.5 mg / m 3 are generated respectively. At the same time, the concentrations at the 4 test points are measured. Each test point is measured three times and the average value is calculated. The deviation between the 4 test points is calculated based on the average value of each concentration. The two test points with the maximum absolute value in each deviation are taken as the test results of the variability of the aerosol generation and mixing device. The test data are shown in Table 4. The test results show that there is good uniformity between the measurement points, not greater than 4.8%.

[0178] Table 4 Uniformity test of 4 test ports (a) Dust generation: 0.2 mg / m 3

[0179]

[0180] (b) Dust generation: 0.4 mg / m 3

[0181]

[0182]

[0183] (c) Dust generation: 0.8 mg / m 3

[0184]

[0185] (d) Dust generation: 1.5 mg / m 3

[0186]

[0187] III. Calibration verification of the performance of the calibrated particulate matter measuring instrument

[0188] The particulate matter measuring instruments to be calibrated are selected as PM 2.5 particulate matter measuring instrument and PM 10 particulate matter measuring instrument respectively, and the performance of the two is calibrated and verified.

[0189] (I) Preparation before calibration

[0190] Preparation before calibration: All fasteners of the measuring instrument to be calibrated should be firmly installed, the connectors should be well connected, all adjustment knobs, buttons and switches should work properly without looseness, the connectors of the cable should be in good contact, the gas path connection should be correct, the seal should be intact without air leakage, and the digital display part should show clearly and completely. After the measuring instrument to be calibrated is powered on, it should be preheated according to the requirements of the operation manual of the manufacturer of the measuring instrument to be calibrated.

[0191] a Instrument requirements

[0192] The instrument operates normally and the measurement function is normal; the instrument must be equipped with a PM 2.5 cutter, PM 2.5 Technical requirements for the cutter: 50% cutting particle size (Da50) = (2.5 ± 0.2) μm, geometric standard deviation of collection efficiency (σg) = 1.2 ± 0.1.

[0193] b Measurement standards and other equipment

[0194] c PM 2.5 PM mass concentration standard device

[0195] Measurement range: (15 - 1000) μg / m 3 ; The expanded uncertainty is not greater than 8% (k = 2).

[0196] d Gas flowmeter: The accuracy level is not lower than 1.5.

[0197] e Stopwatch: The graduation value is 0.01 s.

[0198] f Barometer: The maximum allowable error is ±2.5 hPa.

[0199] g Thermometer: (0 - 100) °C, graduation value 0.1 °C, maximum allowable error ±0.2 °C.

[0200] h High-efficiency air filter: It can filter aerosol particles of 0.3 μm and above.

[0201] i Aerosol particulate matter dust source: Dry ISO 12103-1 A1 ultrafine test dust or ISO 12103-1 A2 fine test dust.

[0202] j PM 2.5 Aerosol generation and mixing device.

[0203] Equipment that can generate aerosol particulate matter with controllable high and low concentrations and uniform mixing; the absolute value of the concentration difference between the standard port (for connecting the mass concentration standard device (200)) and the port to be calibrated (for connecting the particulate matter measuring instrument to be calibrated) is not greater than 6%.

[0204] It is specified that PM needs to be used 2.5The mass concentration standard device serves as an instrument traceability standard, using PM 2.5 The aerosol generator 1 and the mixing device serve as the standard devices for generating and mixing dry ISO 12103-1A1 ultrafine test dust or ISO 12103-2 fine test dust.

[0205] In accordance with the national calibration specification for PM 2.5 mass concentration measuring instruments JJF 1659-2017, verify the instrument, and the PM 10 measurement method also refers to this.

[0206] (2) Calibration methods for each parameter

[0207] 1. Flow indication error

[0208] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated. Turn on the particulate matter measuring instrument to be calibrated and perform sampling. Read the flow indication values shown on the flow standard device and the flow indication values of the particulate matter measuring instrument to be calibrated three times each, and calculate the flow indication error according to formula (1).

[0209]

[0210] In the formula: ΔQ—Flow indication error;

[0211] —Arithmetic mean of the flow indication values of the particulate matter measuring instrument to be calibrated, L / min;

[0212] —Arithmetic mean of the measured indication values of the flow standard device, L / min.

[0213] 2. Average flow deviation

[0214] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated. Turn on the particulate matter measuring instrument to be calibrated and perform sampling. Read the flow indication values three times, and calculate the average flow deviation according to formula (2).

[0215]

[0216] In the formula: ΔQ R —Average flow deviation;

[0217] —Arithmetic mean of the measured indication values of the flow standard device, L / min;

[0218] Q s —Operating point flow of the particulate matter measuring instrument to be calibrated, L / min.

[0219] 3. Flow repeatability

[0220] Connect the flow standard device to the sampling port of the particulate matter measuring instrument to be calibrated. Turn on the particulate matter measuring instrument to be calibrated and perform sampling. Read the flow indication value of the particulate matter measuring instrument to be calibrated, and repeat the measurement 6 times. Calculate the flow repeatability according to formula (3).

[0221]

[0222] In the formula: s r — Flow repeatability;

[0223] Q R,i — The measurement result of the i-th time, L / min;

[0224] — The arithmetic mean of the flow indication values of the particulate matter measuring instrument to be calibrated, L / min;

[0225] n — Number of measurements.

[0226] 4. Flow stability

[0227] Use the flow standard device to measure the initial flow value Q of the particulate matter measuring instrument to be calibrated, and start timing. Then read the flow value once every 20 minutes for a total of 3 times. When the single pumping cycle is less than 1 hour, the interval time can be shortened to read 3 flow indication values within the single pumping cycle. Calculate the sampling flow stability by taking the maximum and minimum values among the 4 flow indication values according to formula (4).

[0228]

[0229] In the formula: ΔQ — Flow stability;

[0230] Q max — The maximum flow indication value of the particulate matter measuring instrument to be calibrated, L / min;

[0231] Q min — The minimum flow indication value of the particulate matter measuring instrument to be calibrated, L / min;

[0232] Q — The initial flow value of the particulate matter measuring instrument to be calibrated, L / min.

[0233] 5. Timing indication error

[0234] During the normal operation of the particulate matter measuring instrument to be calibrated, read and record the time displayed by the particulate matter measuring instrument to be calibrated as the start time t0, and at the same time start the stopwatch to time. When it runs for 1 hour, read and record the display time t1 of the particulate matter measuring instrument to be calibrated and the display time t2 of the stopwatch respectively. Calculate the timing indication error according to formula (5).

[0235] Δt = t1 - t0 - t2 (5)

[0236] Where: Δt—the indicated error of timing, s;

[0237] t0—the start time of the particulate matter measuring instrument to be calibrated, h-m-s;

[0238] t1—the end time of the particulate matter measuring instrument to be calibrated, h-m-s;

[0239] t2—the time indicated by the stopwatch, h-m-s.

[0240] 6. Indicated error of temperature

[0241] Place the standard thermometer at the same height beside the temperature sensor of the particulate matter measuring instrument to be calibrated. After the reading of the standard thermometer is stable, read and record the temperature indication T of the standard thermometer s and the displayed temperature indication T of the particulate matter measuring instrument to be calibrated m , and calculate the indicated error of temperature according to formula (6):

[0242] ΔT = T m -T s (6)

[0243] Where: ΔT—the indicated error of temperature, °C;

[0244] T m —the displayed temperature indication of the particulate matter measuring instrument to be calibrated, °C;

[0245] T s —the temperature indication of the standard thermometer, °C.

[0246] 7. Indicated error of atmospheric pressure

[0247] Place it at the same height beside the pressure sensor of the particulate matter measuring instrument to be calibrated, and read and record the pressure indication p of the standard barometer s and the pressure indication p displayed by the particulate matter measuring instrument to be calibrated m , and calculate the indicated error of atmospheric pressure of the particulate matter measuring instrument to be calibrated according to formula (7).

[0248] Δp = p m -p s (7)

[0249] Where: Δp—the indicated error of atmospheric pressure, kPa;

[0250] p m —the pressure indication of the particulate matter measuring instrument to be calibrated, kPa;

[0251] p s —the pressure indication of the standard barometer, kPa.

[0252] 8. Concentration indication error

[0253] Make the PM 2.5 Aerosol generation and mixing device generate PM with a stable concentration in the range of 25 - 75 μg / m 3 range of PM 2.5 aerosol, and make the PM 2.5 Mass concentration standard device and the particulate matter measuring instrument to be calibrated are respectively connected to the standard port and the port to be calibrated of the PM 2.5 aerosol generation and mixing device. At the same time, set the same sampling time and sampling flow rate. After sampling, record the PM 2.5 Standard concentration value of the mass concentration standard device and the measured value of the particulate matter measuring instrument to be calibrated. Repeat the measurement 2 times, and calculate the mass concentration indication error of the particulate matter measuring instrument to be calibrated at this concentration point according to formula (9).

[0254]

[0255] In the formula: Δc - mass concentration indication error;

[0256] c s —Arithmetic mean of the standard concentration values of the PM 2.5 mass concentration standard device, μg / m 3 ;

[0257] c m —Arithmetic mean of the concentration measured values of the particulate matter measuring instrument to be calibrated, μg / m 3 .

[0258] Then, make the PM 2.5 aerosol generation and mixing device generate PM with mass concentrations in the ranges of 75 - 250 μg / m 3 and 250 - 1000 μg / m 3 range of PM 2.5 aerosol, repeat the above steps, and calculate the mass concentration indication error of the particulate matter measuring instrument to be calibrated at the corresponding concentration points in turn.

[0259] (3) Uncertainty evaluation method

[0260] The particulate matter measuring instrument to be calibrated, such as PM 2.5 / PM 10 particulate matter measuring instrument is an instrument for measuring the mass concentration of solid particulate matter in PM 2.5 / PM 10 aerosol in the air. Therefore, the uncertainty evaluation of the calibration result is mainly for the uncertainty Δc of the mass concentration indication error.

[0261] 1. Calculation of uncertainty

[0262] It can be obtained from Equation (8) that the sources of the uncertainty of the mass concentration indication error mainly include: the uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument and the uncertainty component introduced by the mass concentration standard value. The uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument is mainly introduced by the measurement repeatability of the calibrated particulate matter measuring instrument and the reading resolution of the calibrated particulate matter measuring instrument (which can be ignored). The uncertainty component introduced by the mass concentration standard value mainly includes the uncertainty component introduced by the mass concentration standard device and the uncertainty component introduced by the non-uniformity of the aerosol generation and mixing device. 2.5 The uncertainty component introduced by the mass concentration standard device and the uncertainty component introduced by the non-uniformity of the aerosol generation and mixing device.

[0263]

[0264] In the formula: u r (c m )—The uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument;

[0265] u r (c s )—The uncertainty component introduced by the mass concentration standard value of PM 2.5 The uncertainty component introduced by the mass concentration standard value.

[0266] 2. Evaluation of uncertainty components

[0267] (1) The uncertainty component introduced by the measurement repeatability of the calibrated particulate matter measuring instrument

[0268] The aerosol generation and mixing device generates a standard concentration value, and the calibrated particulate matter measuring instrument measures continuously 6 times. Calculate the measurement repeatability s n-1 , so the uncertainty component u r (c m )

[0269] Can be calculated by the following formula:

[0270]

[0271] In actual calibration, measure twice:

[0272]

[0273] (2) The uncertainty component introduced by the mass concentration standard value

[0274] The uncertainty introduced by the mass concentration standard value mainly consists of the uncertainty introduced by the mass concentration standard device and the uncertainty introduced by the non-uniformity of the aerosol generation and mixing device.

[0275] The uncertainty introduced by the mass concentration standard device is:

[0276] u r1 (c s )

[0277] The uncertainty introduced by the non-uniformity of the aerosol generation and mixing device is:

[0278] u r2 (c m )

[0279] Therefore, the uncertainty introduced by the standard value of the mass concentration can be obtained:

[0280]

[0281] (3) Combine to obtain the uncertainty of the mass concentration indication error

[0282] Calculate using formula (9) to obtain the value of the uncertainty of the mass concentration indication error:

[0283]

[0284] (4) Expanded uncertainty

[0285] The uncertainty of the mass concentration indication error is corrected by a correction factor k greater than 1 to obtain the expanded uncertainty:

[0286] U(Δc) = k·u(Δc) (11)

[0287] For example, take k = 2 and calculate according to formula (11) to obtain the value of the corrected uncertainty of the mass concentration indication error.

[0288] (IV) The specific experiment and uncertainty results are as follows:

[0289] The temperature of the calibration environment is 25.8 °C; the humidity is 27% RH, and the particulate matter measuring instrument to be calibrated is PM 2.5 Particulate matter measuring instrument, the calibration parameters of the mass concentration calibration device are shown in Table 5. Select the particulate matter measuring instruments to be calibrated as PM 2.5 Particulate matter measuring instrument and PM 10 Particulate matter measuring instrument, the calibration process data and results are shown in Table 6.

[0290] Table 5 Calibration parameters of the mass concentration calibration device

[0291]

[0292] Table 6 Calibration process data and results

[0293]

[0294]

[0295] It can be seen from the above test data that for the particulate matter mass measuring instrument based on dual channels, key parameters such as flow rate, temperature, time, and particulate matter mass concentration all meet the preset requirements, and the uncertainty of the particulate matter mass concentration measurement results is better than 9%, k = 2, that is, the standard uncertainty is better than 4.5%, and the mass concentration measurement range is 20 - 1000 μg / m 3 , and the uncertainty of the mass concentration indication error meets the requirement of being better than 5%.

[0296] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy recited.

[0297] In the above detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly recited in each claim. On the contrary, as reflected in the appended claims, the present utility model is in a state with fewer features than all the features of the disclosed single embodiment. Therefore, the appended claims are hereby clearly incorporated into the detailed description, where each claim stands alone as a separate preferred embodiment of the present utility model.

[0298] In order to enable any person skilled in the art to implement or use the present utility model, the above disclosed embodiments have been described. For those skilled in the art, various modification methods of these embodiments are obvious, and the general principles defined herein can also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0299] The foregoing description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but those of ordinary skill in the art should recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, this term is covered in a manner similar to the term "including," as interpreted when "including" is used as a transitional word in a claim. In addition, any use of the term "or" in the specification or claims of a patent is to mean "non-exclusive or."

[0300] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present utility model. It should be understood that the above description is only the specific embodiments of the present utility model and is not used to limit the protection scope of the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A system for calibrating the mass concentration of particulate matter, characterized in that: include: An aerosol generating and mixing device (100) and a mass concentration standard device (200); The aerosol generating and mixing device (100) comprises: a particle generating device (2) and an aerosol generator (1) connected to the particle generating device (2), the aerosol generator (1) having at least two aerosol outlets (10): a first aerosol outlet and a second aerosol outlet, the mass concentration standard device (200) comprising a cutter and a microbalance, the cutter being able to be connected to the microbalance via a pipeline, and the microbalance having a mass sensor; The mass concentration standard device (200) is an oscillating balance method particle measuring instrument; The first aerosol outlet is connected to a cutter of a mass concentration standard device (200); The second aerosol outlet is connected to the particle sampling port of the particle measuring instrument to be calibrated.

2. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 1, characterized in that: The mass concentration standard device (200) comprises a first cutter and a second cutter, a first flow divider is connected behind the first cutter, and a first outlet of the first flow divider can be connected to a first microbalance through a pipeline; the cutter comprises a first cutter and a second cutter, and the first cutter and the second cutter can be used simultaneously, or one of them can be selected to be used; The second outlet of the first flow divider is connected to the second cutter through a pipeline, and the second cutter can be connected to a second microbalance through a pipeline; wherein the first diameter of the particles cut by the first cutter is greater than the second diameter of the particles cut by the second cutter.

3. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 2, characterized in that: The mass concentration standard device (200) further comprises a first dryer arranged after the first flow splitter and before the first microbalance, and the first dryer can be connected to the first flow splitter and the first microbalance respectively through pipelines; The mass concentration standard device (200) also includes a second dryer arranged after the second flow splitter and before the second microbalance, and the second dryer can be connected to the second flow splitter and the second microbalance respectively through pipelines.

4. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 1, characterized in that: The aerosol generating and mixing device (100) further comprises a static electricity neutralization device (9) which can be connected to the particle generating device (2), and the static electricity neutralization device (9) is used to remove static electricity from the particles generated by the particle generating device (2).

5. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 4, characterized in that: The aerosol generating and mixing device (100) further comprises a particle cutting device, one end of which is connected to the particle generating device (2) via a pipeline, and the other end of which is connected to the electrostatic neutralizing device (9) via a pipeline. The particle cutting device is used to screen the generated particles according to their particle size when the diameter of the particles cannot meet the preset diameter requirement, and screen out particles that meet the preset diameter requirement.

6. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 1, characterized in that: The aerosol generating and mixing device (100) further comprises an aerosol mixing chamber (4), which can be connected to the particle generating device (2) and the aerosol generator (1) respectively through pipelines, and the aerosol mixing chamber has a diffusion section (3) at the top, and the diffusion section (3) is a honeycomb structure with apertures, and is used to mix the aerosol.

7. The system for calibrating the measurement capability of the mass concentration of particulate matter according to claim 1, characterized in that: The particle generating device (2) is a wet aerosol generator or a dry aerosol generator.

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