WO2019006017A1 - Instrument de mesure de matière particulaire aéroportée - Google Patents

Instrument de mesure de matière particulaire aéroportée Download PDF

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Publication number
WO2019006017A1
WO2019006017A1 PCT/US2018/039837 US2018039837W WO2019006017A1 WO 2019006017 A1 WO2019006017 A1 WO 2019006017A1 US 2018039837 W US2018039837 W US 2018039837W WO 2019006017 A1 WO2019006017 A1 WO 2019006017A1
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WO
WIPO (PCT)
Prior art keywords
filter
light
sample
light source
air
Prior art date
Application number
PCT/US2018/039837
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English (en)
Inventor
Julien J. CAUBEL
Troy E. CADOS
Thomas W. KIRCHSTETTER
Original Assignee
Caubel Julien J
Cados Troy E
Kirchstetter Thomas W
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/007,513 external-priority patent/US10495573B1/en
Application filed by Caubel Julien J, Cados Troy E, Kirchstetter Thomas W filed Critical Caubel Julien J
Priority to CN201880043201.6A priority Critical patent/CN110799823B/zh
Publication of WO2019006017A1 publication Critical patent/WO2019006017A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G01N15/0606—Investigating concentration of particle suspensions by collecting particles on a support
    • G01N15/0618—Investigating concentration of particle suspensions by collecting particles on a support of the filter type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/59—Transmissivity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • G01N1/2205—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • G01N2001/222—Other features
    • G01N2001/2223—Other features aerosol sampling devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N2015/0042—Investigating dispersion of solids
    • G01N2015/0046—Investigating dispersion of solids in gas, e.g. smoke

Definitions

  • the present application relates to an instrument and method for determining the optical absorption of matter, including black carbon, in the atmosphere.
  • BC Black carbon
  • BC is a primary light- absorbing component of particulate matter generated by biomass and fossil fuel combustion. BC is extremely harmful to both human health and the environment. It has been estimated that airborne particulate matter, including BC, kills an estimated 4 million people per year worldwide. In addition, BC is the second largest contributor to global warming after carbon dioxide. In order to assess EC's impact on climate and human populations, it is necessary to measure both the geographical and vertical distribution of BC in the atmosphere on a large scale .
  • an instrument known as an Aethalometer has been employed to measure the concentration of optically absorbing ⁇ "black” ) suspended particulates in a gas .
  • Such airborne particulate matter (PM) is commonly visualized as smoke or haze and is often seen in ambient air under polluted conditions .
  • Current Aethalometers or BC instruments are usually large bench-top units and are quite expensive to acquire. Furthermore, current BC instruments are not designed to be deployed outdoors and, thus, perform poorly in
  • Aethalometer having a single light source and a single light detector that produces two light paths.
  • a filter collects particles from ambient air in a collection area.
  • a rotating disc allows light from a source to pass alternately through the two light paths and, thus, through the collection and reference areas of the filter. The intensity of light transmitted through the filters are measured and compared to determine the absorption coefficient of the aerosol particles collected on the filter.
  • United States Patent 7,038,765 describes an apparatus and method for measuring black carbon in the atmosphere which utilizes a filter tape that is continually illuminated by a source. Light absorbing aerosol material collected on the tape is continually determined from changes in the optical properties of the tape collection areas, with the aid of known algorithms.
  • United States Patent 9,018,583 shows a method for automatically diagnosing and calibrating a photometric particle analyzer that employs a trio of sensors receiving light from a light source through a filter having a collection and reference portion to produce first and second signals. A third sensor produces a third signal without passing through the filter. Thus, baseline and test measurement comparisons are obtained to provide a diagnostic of the operation of the photometric particle analyzer.
  • United States Patent Publication 2016/0349175 teaches an apparatus receiving an analyte in which two housing portions are clamped together sandwiching a substrate to which analyte is delivered. Optical signals of various wavelengths are passed through the substrate to study analyte properties and are analyzed by optical sensors.
  • United States Patent Publication 2017/0370809 shows a portable air sampling device that utilizes a filter
  • the average mass concentration of aerosol collected by the filter is determined using gravimetric analysis.
  • a low cost, compact instrument for measuring the optical absorption of and concentration of matter, such as particulate black carbon pollutants and other analytes, is needed.
  • Such an instrument should be easy deployed on a massive scale to measure BC distributions both on the ground and in the atmosphere, accurately and reliably under
  • a novel and useful instrument for measuring the optical absorption of airborne matter, such as a black carbon particulates, is herein provided.
  • the instrument or detector of the present application passes a sample of air through a fibrous filter and measures the attenuation of the light through the filter as light absorbing matter, such as BC particles, are
  • the detector also utilizes a bank of light emitting diodes (LEDs) that project light through two separate orifices in the filter material and onto two LEDs
  • a vacuum pump is used to draw ambient air through the instrument or detector. Such sampled air first passes through the signal orifice, trapping suspended particles on the filter and creating a deposit of increasing density. The beam of light from the LEDs is attenuated by BC particles trapped on the filter. After passing through the signal orifice, sample air flows through the reference orifice.
  • the detector of the present invention uses the reference signal generated by airflow recirculation through the reference filter to compensate measurements for environmental
  • measurement deviations resulting from temperature fluctuations are further corrected using a temperature sensor mounted at the sample flow inside the optical cell.
  • the instrument is operated during a training period, and the measurements collected are used to derive a mathematical model of the instrument's temperature
  • This model is uploaded to the instrument's onboard MCU, and light absorption measurements are compensated in real time by use of such onboard temperature sensor.
  • the instrument's temperature dependence is characterized prior to deployment and subsequently
  • the detector of the present application is designed with a short unobstructed path for the flow of sampled air. This flow path allows for greater airflow rates to be pumped through the instrument, requiring less power and, consequently, leading to an increase in the effective
  • the instrument may be designed as a compact, monolithic unit that interfaces with a micro-controller using a minimum number of connections.
  • all components of the instrument may be mounted on a single printed circuit board. The result is a compact instrument that can be easily packaged for a wide variety of application and interfaced easily with other instruments, hardware components, and software protocols.
  • Another object of the present application is to provide an aerosol black carbon detector that may be easily incorporated into both terrestrial and airborne instrument platforms to measure atmospheric BC concentrations.
  • Another object of the present application is to provide an aerosol black carbon detector or instrument that incorporates both hardware and software features that actively compensate light absorption measurements for environmental factors, such as temperature.
  • an aerosol black carbon detector or instrument that incorporates both hardware and software features that actively compensate light absorption measurements for environmental factors, such as temperature.
  • Another object of the present application is to provide an aerosol black carbon detector that is specifically designed to provide BC measurements on a large scale to allow users to better understand and mitigate the impact of BC pollutants on humans and on the environment in general.
  • Another object of the present application is to provide an aerosol black carbon detector that includes an "active reference cell", a reference orifice sampling filtered air, minimizing sensitivity to relative humidity and
  • Another object of the present application is to provide an aerosol black carbon detector that includes a sample flow path which is capable of accommodating high sample flow rates and, thus, increases measurement sensitivity.
  • Another object of the present application is to provide an aerosol black carbon detector that utilizes an auxiliary sensor to measure temperature, humidity, or other environmental factors to compensate for such detector's inherent sensitivity to these factors in real time, thereby increasing the precision and accuracy of desired light absorption measurements.
  • Another object of the present application is to provide a method for characterizing a black carbon detector's dependence on environmental factors, such as temperature or relative humidity.
  • Another object of the present application is to provide an aerosol black carbon detector that is of robust design and is easily manufactured and maintained.
  • a further object of the present application is to provide an aerosol black carbon detector that is compact in size and is easily incorporated into airborne vehicles such as high altitude balloons, ground vehicles, or backpacks carried by humans .
  • a further object of the present application is to provide an aerosol black carbon detector that is symmetrically arranged to allow reversal of a sample air path to reduce maintenance .
  • FIG. 1 is a schematic view of the detector apparatus of the present application.
  • FIG. 2 is a schematic view of the optical cell portion shown in FIG. 1.
  • FIG. 3 is a sectional view of an alternate embodiment of the present application.
  • FIG. 4 is a schematic top plan view of the apparatus depicted in FIG. 3, with filters and photodiodes depicted in broken configuration.
  • FIG. 5 is a sectional view of another embodiment of the optical cell of the present application.
  • FIG. 6 is sectional view of yet another embodiment of the optical cell of the present application.
  • FIG. 7 is a graph depicting voltage outputs from the optical cell depicted in FIG. 2.
  • FIG. 8 is a graph showing black carbon
  • FIG. 9 is a graph depicting temperature and relative humidity measurements over a period of time.
  • FIG. 10 is a graph depicting the relative change of measurements of an optical cell as a function of temperature.
  • FIG. 11 is a graph depicting the relative change of measurements as a function of temperature for another optical cell .
  • FIG. 12 is a graph depicting the relative change of measurements as a function of temperature for yet another optical cell.
  • FIG. 13 is a graph depicting response voltages from an apparatus of the present application having a HEPA filter placed on its air inlet, as uncompensated and temperature compensated values .
  • FIG. 14 is a graph showing black carbon
  • FIG. 15 is a graph depicting optical cell temperature readings during the time period used with the optical cell employed with respect to FIGS. 13 and 14.
  • detector apparatus 10A is shown as being employed with an enclosure or case 12 which may be a
  • a photovoltaic panel 14 may be mounted to enclosure 12 and provide electrical power to apparatus 10A, typically 18 volts, 8 -watts. Photovoltaic panel 14 sends electrical power to charge controller 16 which in turn passes power to battery 18.
  • AUX board 20 includes a microcontroller unit (MCU) 22, real time clock 24, an SD memory card slot 26, and a 2G cellular modem 28.
  • MCU microcontroller unit
  • AUX board 20 possesses conventional power management electronics and necessary hardware for required input and output connections.
  • MCU 22 processes and stores data to the SD memory card and is typically programmed at two second intervals, although measurement intervals greater or equal to one second may be employed.
  • the 2G cellular modem 28 is capable of transmitting data and is typically programmed to transmit 60 one-minute average values every hour to an online database.
  • An optical cell 30 is also found within enclosure 12 and will be more fully discussed as the specification continues.
  • a vacuum pump 32 delivers ambient air samples to optical cell 30.
  • the pump 32 may take the form of a rotary vane pump, although other pumps would suffice.
  • the flow rate of air sampled through apparatus 10A is measured using an air flow or differential pressure sensor 34.
  • differential pressure sensor 34 may entail an Omron D6P mass flow sensor. In any case, sample air enters enclosure 12 as inlet air stream 36 and exits the same as outlet air stream 38.
  • Air flow sensor 34 outputs an analog voltage that is dependent on the mass flow rate of air therethrough. Such data is sent to MCU 22. To calibrate air flow sensor 34, the analog voltage output is recorded while the sample air stream 36 flow rate is simultaneously measured. A pulse-width modulated signal is generated by MCU 22 to control the electrical power delivered to pump 32. In the present configuration, the desired flow rate of pump 22 may be set to anywhere between lOOccm and 250ccm.
  • optical cell 30 is shown in greater detail.
  • Optical cell 30 is found in a case 40 having an air sample inlet 42 and an air sample outlet 44.
  • case 40 includes a chamber 46.
  • Partition 48 lies within chamber 46 and forms sufochambers 50, 52, and 54.
  • Optical cell 30 is also provided with a first filter 56 and a second filter 58 lying apart from first filter 56. Filters 56 and 58 lie within orifices, shown
  • Filters 56 and 58 may take the form of Teflon-coated glass-fiber filters, such as Pallflex Emfab filters. Other filters such as quartz fiber filters may also be used.
  • Filter 56 traps particulate matter, such as black carbon, in airstream 36 and is referred to as the sample filter.
  • Filter 58 receives a clean air stream 57 and passes a clean air stream 60 therefrom.
  • Filter 58 is referred to as the reference filter.
  • Air reaching reference filter 58 is substantially free of black carbon since filters 56 and 58 have a particle removal efficiency of 99.9%. As shown in FIG. 2, black carbon deposits 62 are found on sample filter 56. When sample filter 56 reaches a high optical attenuation value, filters 56 and 58 are replaced.
  • Optical cell 30 is also fashioned with light emitting diodes (LEDs) 64 and 66, LED 64 passes light through sample filter 56 such that light ray 66 is attenuated by the presence of BC deposits 62.
  • LED 64 passes through sample filter 56 such that light ray 66 is attenuated by the presence of BC deposits 62.
  • light ray 70 passes through reference filter 58 and is unaffected by BC concentrations in air stream 36, air stream 60 being filtered as heretofore described.
  • LEDs 64 and 66 may operate at a central wavelength of 880nm, where black carbon is the predominant species to absorb light. However, light at any wavelength may be employed according to the particular species being analyzed.
  • a sample light ray 68 and a reference light ray 70 pass to photodiodes 72 and 74.
  • Photodiodes 72 and 74 measure the intensity of the sample and reference light rays 68 and 70, respectively, and produce voltage signals 76 and 78 that are linearly proportionally to the intensity of light transmitted through filters 56 and 58, respectively. Where multiple wavelength light is used, photodiodes 72 and 74 may take the form of spectrometers. An analog-to-digital
  • ADC 80 digitizes voltage signals 76 and 78 and sends the same to MCU 22.
  • RH/T temperature sensor 82 is mounted directly in subchamber 54 directly in the flow path of air stream 60 adjacent the sample photodiode 72 and the reference photodiode 7 .
  • RH/T sensor 82 provides measurements required to compensate apparatus 10A for environmental measurements artifacts to MCU 22, which will be discussed in greater detail as the
  • ADC 80 and MCU 22 provide a
  • Apparatus 10B includes an optical cell 84 that is placed in a case 86 and further includes printed circuit board 88 that serves as a single base or mount for a sole light emitter 90 and a photo detector 92. In certain cases, all the components shown in FIG. 1 may be mounted to a single base such as a PCB.
  • Optical cell 84 also is provided with an aerosol filter 94 which lies within chamber 96 of optical cell 84.
  • a glass layer 98 is positioned below a reflector 100.
  • Airflow stream 102 passes through inlet 104 of case 86, travels through aerosol filter 94, and flows out of case 86 through outlet 106 as filtered air stream 107.
  • Light path 108 indicates that light originates with light emitter 90, impinges and returns from beam splitting reflector 100, passes through aerosol filter 94, and hits photodetector 92.
  • photodetector 92 generates a signal that is indicative of the presence of light absorbing particulate matter such as black carbon on aerosol filter 94.
  • light emitter 90 also produces a second light path 110 which hits a filter 111 and photodetector 112 below.
  • RH/T sensor 113 is also found in embodiment 10B.
  • Filtered air stream 107 is passed through filter 111 in the same manner as shown in FIG. 2, with respect to apparatus 10A.
  • photodetector 112 serves as a source of reference signals.
  • the sample signals from photodetector 92 and the reference signals from photodetector 112 are processed in the same manner as shown in FIGS. 1 and 2 with respect to signals 68 and 70 of apparatus 10A. It should be noted that using a sole light emitter 90 eliminates intensity variation inherent with the dual light emitters of FIGS. 1 and 2.
  • FIG. 5 illustrates another embodiment IOC of an optical cell of the present application used in lieu of optical cell 30, FIG. 1.
  • a case or housing 110 encompasses a filter 112 which lies between LED 114 and photodetector 116, housing 110 includes an ambient air inlet 118 and outlet 120.
  • Air path 122 shows the route of air passing through filter 112 and housing 110.
  • Relative humidity/temperature (RH/T) sensor 124 also lies within housing 110 and is used to compensate the environmental factor sensitivity of light absorption
  • Light emanating from LED 114 travels via light path 126, through glass 115, filter 112, and impinges on photodetector 116.
  • Light ray 126 is attenuated by BC deposits 125.
  • Light ray 126 transforms into sample signal 128 at photodetector 116.
  • RH/T sensor 124 generates second and third signals.
  • Embodiment 10D has been operated during a "training period” , discussed hereinafter.
  • the measurements collected during such "training period” are used to derive a mathematical model of the instrument's RH/T sensitivity.
  • This model is uploaded to MCU 22, and RH/T measurements are used to compensate light absorption measurements in real time, eliminating the need for the reference LED, filter and photodiode .
  • embodiment IOC is immunized from environmental fluctuations using RH/T sensor 122 and the mathematical model.
  • the calculation of BC is based on comparing the value of a current sample signal 128 to the value of a previous sample signal. The previous sample signal value would then serve as a reference value.
  • the temperature dependence of reference components and noise amplification is eliminated in embodiment IOC, as is the case with other embodiments found herein.
  • intensity variation and noise amplification inherent in dual light emitters and dual photodetectors is eliminated .
  • FIG. 6 represents yet another embodiment 10D of the present application.
  • a housing 130 encloses sample filter 132 and reference filter 134.
  • Air path 136 extends through housing inlet 138, filters 132 and 134, and to housing outlet 140.
  • LEDs 142 and 144 pass light through glass elements 146 and 148, filters 132 and 134, to a single photodiode 142.
  • RH/T sensor 144 lies adjacent photodiode 142.
  • BC deposits 146 accumulate on sample filter 132.
  • By alternately turning LEDs 142 and 144 "on" and “off” photodetector 142 will alternately generate sample and reference signals 148 and 150. Again, measurement variation and noise amplification problems are avoided by using a single photodetector.
  • sample and reference signal are processed in the apparatus shown on FIG. 1 where optical cell embodiment 10D is
  • air flow sensor 34 downstream of optical cell 30 measures the mass flow rate of air stream 60.
  • MCU 22 through a signal from sensor 34, generates a pulse-width modulated signal to control the electrical power delivered to vacuum pump 32.
  • Light emitting diodes 64 and 66 produce sample and reference light rays 68 and 70,
  • Photodiodes 72 and 74 generate electrical voltages that are linearly proportional to the intensity of light transmitted through sample filter 56 and reference filter 58, respectively.
  • the analog voltage measurements from photodiodes 72 and 74 are digitized using analog-to-digital converter 80 that produces a digital signal processed by MCU 22.
  • MCU 22 eventually determines a ratio of BC mass concentration in air stream 36 through the measured optical attenuation between light rays 68 and 70, which is expressed as the natural log ratio of the reference to sample voltage outputs.
  • the following equation represents such calculation :
  • V smp i(t) and V re f t)(V) are the optical, cell, sample and reference voltage outputs 76 and 78 at each measured time step t , respectively.
  • the Black Carbon mass concentrations (pg/m 3 ) at each measurement time interval are calculated based on
  • the filters 56 and 58 may be placed in orifices that are circular and may typically have a diameter of 0.003175m and a
  • Q is the mass flow rate of air stream 36 through optical cell 30 measured by differential pressure sensor 34 which lies downstream of optical cell 30.
  • the flow rate of the air stream 36 through optical cell 30 is typically set between lOOcc/min and 250cc/min.
  • Flow sensor 34 measures the flow rate.
  • MCU 22 uses this information to modulate the power delivered to pump 32.
  • MAC is the mass attenuation coefficient of BC which is set at 12.5m 2 /g in the present case. However, a different MAC value would be used with a different wavelength of light, or species of interest.
  • Apparatus 10A was operated outdoors with a High
  • FIGS. 7-9 represent data obtained therefrom.
  • PIG. 7 shows that the sample and
  • reference output voltages 76 and 78, FIG. 2 are clearly dependent on ambient conditions, oscillating in sync with the diurnal trends in temperature and relative humidity.
  • FIG. 9 shows such results. It is theorized that the output voltage oscillations shown in FIG. 7 are likely the result of
  • LEDs 64 and 66 are rated to dim 0.3% for every 1°C temperature rise, which is approximately represented by the observation of FIG. 5.
  • the temperature sensitivity of LEDs 64 and 66 play a major role in the accuracy of apparatus 10A.
  • Photodiode sensitivity the voltage output per watt of incident light intensity
  • the measurements of apparatus 10A essentially measure the temperature of the air flowing through optical cell 30, but it is assumed that any electronics associated with device 10A are at a similar temperature.
  • BC concentrations are much larger than ⁇ 0.3pg/m 3 , then further compensation may not be necessary.
  • temperature compensation is employed to further reduce environmental sensitivity.
  • V(t is the photodiode voltage at time t
  • V(0 is the first voltage logged during the particle-free sampling event.
  • FIGS. 10-12 represent three detector apparatuses similar to apparatus 10 and are
  • FIGS. 10-12 are plotted as a function of sensor temperature for the noted three optical cells, and linear regression factors (slope, intercept, and R 2 ) are shown.
  • the temperature sensitivities of an optical cell's sample and reference channels at the sample and reference filters, such as filters 56 and 58 of apparatus 10 are not often equal. Therefore, the ratio of these slopes (m smp i/m ref , hereinafter referred to as "slope ratio") is often either greater than or less than unity.
  • ABCD1 of FIG. 10 has a slope ratio of 0.57 indicating that the sample voltage output is less temperature sensitive than the
  • V comp (t) is the temperature-compensated voltage output (V)
  • Tt) is the sample flow temperature (0°C)
  • m C "1 ) and b are the slope and intercept of the linear regression, respectively. Rearranging the above equation yields an equation that allows the photodiode voltage, Vf) , to be compensated using real time temperature measurements:
  • BC concentrations calculated using temperature- compensated sample and reference voltage outputs from the above equation are generally significantly less sensitive to temperature fluctuations. It has been observed that there is considerable variability in the temperature sensitivity of optical cells, such as optical cell 30. This is due to the variations in LEDs 64 and 66, photodiodes 72 and 74, and related circuitry found on AUX board 20. The temperature sensitivity and linear regression coefficients found in the above equation were determined uniquely for each individual ABCD optical cell noted in FIGS. 10-12. The slope and intercept for both photodiode outputs, such as photodiodes 72 and 74 of optical cell 30, were stored on SD cards placed in slot 26 and were assigned to each optical cell used to generate FIGS. 10-12.
  • linear regression coefficients for each optical cell were uploaded to MCU 22 to compensate BC measurements in real time as a function of measured temperature.
  • linear regression factors ' must be determined uniquely for each ABCD optical cell used to measure airborne light absorbing matter.
  • the same "training period" and compensation may be obtained for relative humidity as an environmental factor.
  • FIGS. 13-15 illustrate temperature-compensated ⁇ T- Comp) responses as well as uncompensated (Raw) responses for the ABCD utilized to generate the information on FIGS. 7 - 9 .
  • temperature-compensated voltage outputs steadily maintained their initial values, FIG. 13, and temperature compensated BC concentrations exhibited a diurnal trend, FIG. 14. Such diurnal trend is typically in the
  • FIG. 13 represents reference and sample voltage outputs from an optical cell, such as optical cell 30.
  • FIG. 14 compares uncompensated and
  • FIG. 15 shows cell temperature for the optical cells used to generate the information in FIGS. 13 and 14 over a period of 14 days . All the data gleaned from FIGS. 13-15 were provided on a sixty minute time base. The method of the working example may be employed with the various embodiments 10A-10D of the present application.

Abstract

L'invention concerne un appareil pour mesurer l'absorption optique de matière aéroportée ou d'autres espèces absorbant la lumière dans un flux d'air d'échantillon. L'appareil comprend un trajet d'écoulement à travers un filtre fibreux pour collecter des espèces absorbant la lumière dans l'air échantillonné. Le flux d'air filtré peut ensuite passer à travers un second filtre, utilisé pour des mesures de référence. Au moins une source de lumière vient en contact avec le filtre, générant un ou deux signaux optiques pour déterminer l'absorption de la lumière de matière particulaire ou d'autres espèces dans le flux d'air échantillonné. L'appareil comprend au moins un capteur auxiliaire dans le trajet d'écoulement d'échantillon pour surveiller un facteur environnemental, tel que la température. Pendant une période d'apprentissage, un modèle mathématique de la sensibilité environnementale de l'appareil est déduit. A l'aide du modèle mathématique et des mesures provenant du capteur auxiliaire, des signaux optiques sont compensés en temps réel pour augmenter la précision et la précision des mesures d'absorption de lumière enregistrées dans des conditions environnementales fluctuantes.
PCT/US2018/039837 2017-06-28 2018-06-27 Instrument de mesure de matière particulaire aéroportée WO2019006017A1 (fr)

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CN201880043201.6A CN110799823B (zh) 2017-06-28 2018-06-27 用于确定大气中的包括炭黑在内的物质的光吸收的仪器和校准方法

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US62/526,237 2017-06-28
US201762526770P 2017-06-29 2017-06-29
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US16/007,513 2018-06-13
US16/007,513 US10495573B1 (en) 2018-06-13 2018-06-13 Instrument for measuring airborne particulate matter

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