Particulate matter sensor and method thereof
阅读说明:本技术 颗粒物质传感器及其方法 (Particulate matter sensor and method thereof ) 是由 肯尼斯·法尔梅 托马斯·爱德华·肯尼迪 于 2018-04-16 设计创作,主要内容包括:各种实施方式包括用于测量和校准光学颗粒光谱仪以报告质量浓度的方法和系统。在一个实施方式中,光学颗粒光谱仪用于测量采样的载粒气流中的颗粒物质的浓度。与光谱仪流体连通的颗粒分流器以预定间隔使载粒气流的至少一部分分流。在一个示例中,质量过滤器接收载粒气流的该一部分,并且过滤气流中大于预定颗粒尺寸的一部分颗粒。质量传感器测量从质量过滤器或颗粒分流器接收到的该部分颗粒的质量,并且使用校准通信环路将所测量的质量提供至光谱仪以将校正因子应用于从光学颗粒光谱仪报告质量浓度。公开了其他方法和系统。(Various embodiments include methods and systems for measuring and calibrating optical particle spectrometers to report mass concentrations. In one embodiment, the optical particle spectrometer is used to measure the concentration of particulate matter in a sampled particulate laden gas stream. A particle diverter in fluid communication with the spectrometer diverts at least a portion of the flow of the particle-laden gas at predetermined intervals. In one example, a mass filter receives the portion of the particulate laden air stream and filters a portion of particles in the air stream that are larger than a predetermined particle size. The mass sensor measures the mass of the portion of particles received from the mass filter or particle splitter and provides the measured mass to the spectrometer using a calibration communication loop to apply a correction factor to report mass concentration from the optical particle spectrometer. Other methods and systems are disclosed.)
1. A system for measuring a flow of sampled particulate laden gas, the system comprising:
an optical particle spectrometer for measuring the concentration of particulate matter in the sampled particulate laden gas stream;
a particle splitter in fluid communication with the optical particle spectrometer, the particle splitter splitting at least a portion of the particle-laden gas stream at predetermined intervals;
a mass sensor for measuring a mass of a portion of the particles in the diverted particle-laden gas stream received from the particle diverter; and
a calibration communication loop for providing a measured quality of the particle to the optical particle spectrometer.
2. The system of claim 1, further comprising a mass filter coupled upstream of the mass sensor to receive a portion of the particulate laden gas stream and filter a portion of particles in the particulate laden gas stream that are greater than a predetermined particle size.
3. The system of claim 1, further comprising a mass filter coupled upstream of the optical particle spectrometer to receive the sampled particle-laden gas stream and filter a portion of particles in the particle-laden gas stream that are greater than a predetermined particle size.
4. The system of claim 2 or 3, further comprising a particle diluter upstream of and in fluid communication with at least one of the mass filter and the mass sensor to dilute the concentration of the carrier gas stream.
5. The system of claim 1, wherein the mass sensor is a mass concentration measurement device to provide a correction factor to the optical particle spectrometer over the calibration communication loop to calibrate the optical particle spectrometer to report an equivalent mass concentration measurement.
6. The system of claim 5, wherein calibration of the optical particle spectrometer is performed with a single correction factor.
7. The system of claim 6, wherein the single correction factor is selected for a predetermined range of particulate matter sizes.
8. The system of claim 5, wherein calibration of the optical particle spectrometer is performed with a plurality of correction factors.
9. The system of claim 8, wherein each of the plurality of correction factors is selected for a different predetermined particulate matter size range.
10. The system of claim 5, wherein calibration of the optical particle spectrometer is performed using a particular type of aerosol for a particular sampling environment.
11. The system of claim 1, wherein the particle diverter is a fluid switching device for intermittently diverting at least a portion of the flow of the particulate-laden gas to the mass sensor.
12. The system of claim 1, wherein the mass sensor is a thin film bulk acoustic resonator.
13. The system of claim 1, wherein the mass sensor is a quartz crystal monitor.
14. A system for measuring a flow of sampled particulate laden gas, the system comprising:
an optical particle spectrometer for measuring a concentration of particulate matter in the sampled particulate laden gas stream;
a mass sensor for measuring a mass of a portion of the particles received from at least a portion of the sampled particulate laden gas stream; and
a calibration communication loop between the optical particle spectrometer and the mass sensor for providing the measured mass from the mass sensor to the optical particle spectrometer to calibrate the optical particle spectrometer for equivalent mass concentration measurements.
15. The system of claim 14, further comprising a shunt inlet port coupled upstream of both the optical particle spectrometer and the mass sensor.
16. The system of claim 15, wherein the split flow inlet port is a split sampling port configured to provide a smaller portion of particulate matter to the mass sensor than to the optical particle spectrometer.
17. The system of claim 15, wherein the split stream inlet port is configured to provide substantially equal portions of the sampled particle laden gas stream to the optical particle spectrometer and the mass sensor substantially simultaneously.
18. The system of claim 15, wherein the mass sensor is selectable to sample the true mass of the flow of particulate carrier gas in at least one of two modes from a group consisting of an intermittent sampling mode and a continuous sampling mode.
19. A method of calibrating an optical particle spectrometer for equivalent mass concentration measurements, the method comprising:
sampling the particle-laden gas stream;
diverting a controlled portion of the particulate laden gas stream to a mass sensor;
measuring at least one mass concentration of particulate matter in the particulate laden gas stream below at least one particle size cut-off; and
communicating at least one measured mass concentration of the particulate matter to the optical particle spectrometer to provide a calibration factor to the optical particle spectrometer.
20. The method of claim 19, further comprising reporting equivalent mass concentration measurements from the calibrated optical particle spectrometer.
Technical Field
The inventive subject matter disclosed herein relates to particulate matter sensors, and more particularly, to optical particle spectrometers that are calibrated in substantially real time by mass concentration sensors.
Background
Atmospheric Particulate Matter (PM) pollutants are small solid particles or small droplets suspended in the atmosphere. The particles or droplets may include, for example, diesel exhaust, tobacco smoke, volcanic ash, bacteria, mold spores, and pollen. PM contaminants have diameters ranging from tens of micrometers (μm) to a few nanometers. Measured, for example, at 2.5 μm or less in diameter (PM)2.5) PM contaminants of (a) are particularly harmful to humans because they can penetrate deep into the human respiratory system and may even enter the bloodstream. The determination of the particulate matter relates to the mass of the particles per unit volume, which is indicated as a mass concentration value.
Thus, mass concentration provides an indication of the actual mass of particulate matter per unit volume in a given environment (e.g., within a tunnel on an interstate highway system or other transportation route with heavy traffic (e.g., car, diesel-powered train, bus route, etc.), the interior of a car or bus, the interior of a factory floor, or many other environments). Mass concentration value generalOften in micrograms per cubic meter (μ g/m)3) Is reported in units. For example, in a congested or polluted metropolitan area, the mass concentration of particulate matter may be about 200 μ g/m3Or higher. The mass concentration value may also be related to a given particle size, e.g. PM10(10 μm and less), PM2.5(2.5 μm and less) or PM1(1 μm and less). Public health agencies typically report mass concentration statistics with 10% accuracy or better.
The mass concentration value may be compared to a particle count (e.g., as reported by an Optical Particle Counter (OPC) or Optical Particle Spectrometer (OPS)), as OPC may simply provide a total number of particles or a total number of particles sorted by particle size range (e.g., using OPS). Thus, OPC or OPS cannot measure true mass, cannot account for the density of the measured particles, cannot generally account for the reflectivity of the particles, and so on. However, typically these devices are used to provide an estimate of true mass by making assumptions about particle density and reflectivity, but the accuracy of such estimates may shift by a factor of two or more. Nonetheless, OPC and OPS devices are generally more compact, less expensive, and easier to operate and maintain than many real mass concentration measurement devices. Further, recently developed micro-devices measure mass concentration based on a change in resonance frequency at the time of particle deposition, but have the following problems: the micro device may load particles over time, eventually changing the response characteristics of the particles, and thus the micro device cannot be continuously used for a long period of time. In contrast, the OPS and OPC devices measure particles passing through the OPS and OPC devices, so the OPS and OPC devices are not loaded with particles. Therefore, there is a need for a method to accurately and precisely correlate the total number of particles concentration reported by OPC or OPS with the true mass concentration value.
Drawings
Fig. 1A shows a diagram of a particulate matter sensor calibration system according to an embodiment of the disclosed subject matter;
fig. 1B shows a diagram of an alternative configuration of a particulate matter sensor calibration system, in accordance with an embodiment of the disclosed subject matter;
fig. 1C illustrates a diagram of a particulate matter sensor calibration system in accordance with an alternative or supplemental embodiment of the disclosed subject matter;
fig. 1D illustrates a diagram of a particulate matter sensor calibration system in accordance with another alternative or supplemental embodiment of the disclosed subject matter; and
FIG. 2 illustrates an embodiment of an example calibration method that may be used with any of the systems of FIGS. 1A-1D.
Detailed Description
As mentioned above, Optical Particle Spectrometer (OPS) devices are often used to determine an approximation of the mass concentration of Particulate Matter (PM) in a given environment. The disclosed subject matter combines OPS with a particle mass concentration measurement device, such as a thin Film Bulk Acoustic Resonator (FBAR) or a quartz crystal monitor (QCM, also known as a quartz crystal microbalance), to provide a correction factor for the "equivalent mass" concentration determined by the OPS, thereby calibrating the OPS for effective mass concentration measurements for one or more reported particle size ranges. One feature of other devices, such as FBAR devices and QCM devices, is that they can be made very small and inexpensive for use in applications where miniaturization and mass production are desired. Unlike OPS devices, however, FBAR devices and QCM devices tend to load particles over time, rendering reported values inaccurate.
In an embodiment, a single correction factor is utilized (e.g., a single point such as PM for a given PM value)2.5) The OPS (for one or more reported granularity ranges reported by the OPS) is calibrated. Typically, the correction factor is offset by a constant multiple or constant factor so that a single correction factor can be used to determine the difference. However, in other embodiments described herein, multiple correction factors may be utilized (e.g., in PM)2.5And PM10PM value of) to perform calibration. Additional PM values (e.g., PM) may also be utilized1) To provide one or more correction factors. As known in the art, PM values are not binding (bin) ranges or size ranges of particles. Instead, the PM value relates to the overall mass of particles below a certain sizeFor example, PM2.5Involving the overall mass of the particles below 2.5 μm). Thus, more accurate and precise measurement of PM mass concentration by OPS is possible using the systems and methods provided herein.
Various types of OPS devices are available and may be used with the various embodiments described herein. For example, optical particle sizers of TSI 3330 type or TSI 8520DUSTTRAKTMModel aerosol monitors (both available from TSI Incorporated, shorevew, Minnesota, USA) utilize light scattering technology to determine mass concentration in real time. The aerosol sample is introduced into the sensing chamber in a continuous stream. A portion of the aerosol stream is illuminated by a small laser beam. Particles in the aerosol stream scatter light in all directions. In some cases, a lens, for example, located at about 90 ° to both the aerosol stream and the laser beam, collects some of the scattered light and focuses it onto a photodetector. The detection circuit converts the light into a voltage proportional to the amount of scattered light, which in turn is proportional to the mass concentration of the aerosol. The voltage is read by a processor and multiplied by an internal calibration constant to produce a mass concentration. Internal calibration constants are 3330OPS or DUSTTRAKTMThe ratio of the voltage response of the monitor to the known mass concentration of the test aerosol is determined (the monitor can be calibrated against a weight reference using ISO standard 12103-1, a1 test Dust (e.g., a respirable fraction such as "Arizona Road Dust"). If a high accuracy of mass concentration readings is required, 3330OPS or DUSTTRAK may be recalibrated for environments where a particular aerosol type is dominantTMA monitor. Similar types of calibration can also be achieved using OPS type devices available from other manufacturers.
Other types of particle measurement sensors are also available. For example, PM2.5Particle sensors such as PMS 7003 are available from shangtao technologies (salyu, Beijing, China, post-cisterm) (Plantower (Houshayu, Shunyi diagnosis, Beijing, China)) and a number of other manufacturers.
Mass measuring device and mass concentration measuring device in, for example, atmospheric aerosol scienceAre known. The mass concentration means may comprise, for example, a true mass filter based
Microbalances (available from Thermo Fisher Scientific; Franklin, Massachusetts, USA) available from seemer feishi technologies, Franklin, Massachusetts, USA). As mentioned above, other types of mass-measured concentration devices include, for example, QCM or FBAR devices.QCM is used for micro-weighing and consists of a quartz plate with a mechanical resonance frequency that is inversely proportional to the thickness of the plate. Since the Q value of quartz is very high (low internal friction), the resonance frequency can be measured electrically by the piezoelectric effect. If the mass to be measured is applied to the resonator, for example in the form of PM, its effect on frequency is very close to the increase in the equivalent mass of quartz. The added mass can be determined by converting the frequency change to an equivalent quartz thickness and then to mass with the help of a known quartz density.
In one form, an FBAR device may be fabricated by, for example, sputter depositing a piezoelectric material such as zinc oxide (ZnO) or aluminum nitride (AlN) onto a film formed on a semiconductor substrate. The combination of the piezoelectric layer and the membrane forms an acoustic structure that resonates at a particular frequency. A ZnO film with a thickness of a few microns produces a resonator with a fundamental frequency of about 500 MHz. When particles adhere to a mass-sensitive element of an FBAR device, the fundamental frequency of the element decreases in proportion to the mass of particles reaching and adhering to the element. When particles are deposited onto the mass-sensitive element, the frequency at which the device oscillates is proportionally reduced, and the amount of increase in mass due to the particles is calculated from the reduction in frequency.
As described in more detail below, OPS serves as a continuous particle "mass" measurement component of the inventive subject matter, and may intermittently or continuously use a mass concentration measurement device (mass sensor) to measure true mass in the same environment, thereby determining the correction factor CfTo correct the OPS to a true mass measurement. The combination of these two device types provides, for exampleThe following benefits: (1) robustness of OPS measurements; (2) the improved accuracy and precision achieved by real mass measurement devices, while for example overcoming disadvantages of OPS such as: (1) if the true mass is unknown, it may result in less accurate OPS measurements; and (2) the fact that: real mass measurement components may not be suitable for continuous undiluted measurements (undiluted measurements) because they may load particles over time, which may lose sensitivity.
Thus, the disclosed subject matter provides an intermittent or continuous, substantially real-time, in-situ, true mass measurement to enable determination of an accurate correction factor for the equivalent mass concentration reported by the OPS. The inventive subject matter described herein will find use in many applications where improved accuracy of mass concentration measurements is desired, as well as other applications requiring miniaturization and low cost of instrumentation, such as automotive cabin air quality sensing. It is well known that the error in particle mass concentration calculated using OPS can reach 20% or more depending on the difference between the sampled material and the material used to calibrate the OPS. Correction factors that are multiplier constants or functions that make the OPS output more consistent with the actual mass measured are typically used to compensate for this error. The actual mass is usually determined using cumbersome and expensive reference devices such as the following: the conical element oscillating microbalance (TEOM) mentioned above, which measures the true particle mass concentration; or a beta-attenuation monitor (BAM), which is a U.S. federal equivalent mass concentration measurement method that determines mass based on the absorption of beta radiation by solid particles extracted from flowing air.
Referring now to fig. 1A, a diagram of a particulate matter
A
The
The
In this embodiment utilizing a cascade impactor, each of the impact plates may be one of the various mass sensing devices described above (e.g., each plate includes a separate FBAR device or QCM device). Calculating a given cutoff particle size for each of the impingement plates (e.g., the measured particulate mass concentration output after stage I relates to PM) using control equations for inertial impactors known in the art10Size, particle mass concentration measured after stage IIDegree of output related to PM2.5Size, etc.). The actual mass concentration of the particles, which is derived from the inertial impactor control equation, may then be fed back to the OPS103 and the correction factor C usedfFor one or more particle size ranges (e.g., PM) associated with the mass of all particles below a certain particle size2.5) The measured particle count is correlated to mass concentration. The correction factor applied to the particle concentration measured by OPS may be, for example, the ratio of the particle concentration measured by
In other embodiments, the
In other embodiments, the
Referring now to fig. 1B, a diagram of a particulate matter
As compared to the particulate matter
After reading and comprehending the disclosure provided herein, one of ordinary skill in the art will fully understand when to use the optional
However, there are other cases as follows: it may be desirable for OPS103 to measure the overall particle number concentration and for
Referring now to fig. 1C, a diagram of a particulate matter
With continued reference to fig. 1C, the particulate matter
Additionally,
In one embodiment, split
In other embodiments, split
In either embodiment, the split
In other embodiments, split
Thus, in one embodiment, the
In other embodiments,
Referring now to fig. 1D, a system diagram of a particulate matter sensor calibration system 140 is shown, in accordance with an alternative or supplemental embodiment of the disclosed subject matter. The particulate matter sensor calibration system 140 is shown to include a split
The
The
In one embodiment, split
FIG. 2 illustrates an embodiment of an
Referring also to fig. 1A,
At
At
At
Included in the disclosed subject matter provided herein are various system and method diagrams describing various embodiments of particulate matter sensor calibration systems. Accordingly, the above description includes illustrative examples, devices, systems, and methods that implement the disclosed subject matter. In the description, for purposes of explanation, numerous specific details are set forth in order to provide an understanding of various embodiments of the inventive subject matter. It will be apparent, however, to one skilled in the art that various embodiments of the present subject matter may be practiced without these specific details. In other instances, well-known structures, materials, and techniques have not been shown in detail in order not to obscure the various illustrated embodiments.
As used herein, the term "or" may be interpreted in an inclusive or exclusive sense. Additionally, although various exemplary embodiments discussed herein focus on a particular manner for generating and calibrating a particulate matter sensor calibration system, other embodiments will be understood by those of ordinary skill in the art upon reading and understanding the provided disclosure. Moreover, upon reading and understanding the disclosure provided herein, one of ordinary skill in the art will readily appreciate that various combinations of the techniques and examples provided herein may be applied in the various combinations.
While various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As described above, each of the various portions may be interrelated, and each portion may be used alone or in combination with other particulate matter sensor calibration system embodiments discussed herein.
Thus, it will be apparent to those of ordinary skill in the art that many modifications and variations are possible in light of the disclosure provided herein. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing description. Portions and features of some embodiments may be included in or substituted for those of others. Such modifications and variations are intended to fall within the scope of the appended claims. Accordingly, the disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
The Abstract of the disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing detailed description, it can be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure should not be construed as limiting the claims. Thus the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.
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