scholarly journals Laboratory Evaluation of Low-Cost Optical Particle Counters for Environmental and Occupational Exposures

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4146
Author(s):  
Sinan Sousan ◽  
Swastika Regmi ◽  
Yoo Min Park
Keyword(s):  
Low Cost ◽  
Road Dust ◽  
Occupational Exposures ◽  
Laboratory Evaluation ◽  
Sensor Calibration ◽  
Reference Instrument ◽  
Highly Correlated ◽  
Occupational Settings ◽  
Aerosol Types ◽  
Mass Concentrations

Low-cost optical particle counters effectively measure particulate matter (PM) mass concentrations once calibrated. Sensor calibration can be established by deriving a linear regression model by performing side-by-side measurements with a reference instrument. However, calibration differences between environmental and occupational settings have not been demonstrated. This study evaluated four commercially available, low-cost PM sensors (OPC-N3, SPS30, AirBeam2, and PMS A003) in both settings. The mass concentrations of three aerosols (salt, Arizona road dust, and Poly-alpha-olefin-4 oil) were measured and compared with a reference instrument. OPC-N3 and SPS30 were highly correlated (r = 0.99) with the reference instrument for all aerosol types in environmental settings. In occupational settings, SPS30, AirBeam2, and PMS A003 exhibited high correlation (>0.96), but the OPC-N3 correlation varied (r = 0.88–1.00). Response significantly (p < 0.001) varied between environmental and occupational settings for most particle sizes and aerosol types. Biases varied by particle size and aerosol type. SPS30 and OPC-N3 exhibited low bias for environmental settings, but all of the sensors showed a high bias for occupational settings. For intra-instrumental precision, SPS30 exhibited high precision for salt for both settings compared to the other low-cost sensors and aerosol types. These findings suggest that SPS30 and OPC-N3 can provide a reasonable estimate of PM mass concentrations if calibrated differently for environmental and occupational settings using site-specific calibration factors.

scholarly journals Integration and calibration of non-dispersive infrared (NDIR) CO<sub>2</sub> low-cost sensors and their operation in a sensor network covering Switzerland

2020 ◽  
Vol 13 (7) ◽  
pp. 3815-3834 ◽  
Author(s):  
Michael Müller ◽  
Peter Graf ◽  
Jonas Meyer ◽  
Anastasia Pentina ◽  
Dominik Brunner ◽  
...  
Keyword(s):  
Data Processing ◽  
Sensor Network ◽  
Low Cost ◽  
Significant Loss ◽  
Sensor Calibration ◽  
Data Filtering ◽  
Ambient Conditions ◽  
Term Operation ◽  
Reference Instrument

Abstract. More than 300 non-dispersive infrared (NDIR) CO2 low-cost sensors labelled as LP8 were integrated into sensor units and evaluated for the purpose of long-term operation in the Carbosense CO2 sensor network in Switzerland. Prior to deployment, all sensors were calibrated in a pressure and climate chamber and in ambient conditions co-located with a reference instrument. To investigate their long-term performance and to test different data processing strategies, 18 sensors were deployed at five locations equipped with a reference instrument after calibration. Their accuracy during 19 to 25 months deployment was between 8 and 12 ppm. This level of accuracy requires careful sensor calibration prior to deployment, continuous monitoring of the sensors, efficient data filtering, and a procedure to correct drifts and jumps in the sensor signal during operation. High relative humidity (> ∼85 %) impairs the LP8 measurements, and corresponding data filtering results in a significant loss during humid conditions. The LP8 sensors are not suitable for the detection of small regional gradients and long-term trends. However, with careful data processing, the sensors are able to resolve CO2 changes and differences with a magnitude larger than about 30 ppm. Thereby, the sensor can resolve the site-specific CO2 signal at most locations in Switzerland. A low-power network (LPN) using LoRaWAN allowed for reliable data transmission with low energy consumption and proved to be a key element of the Carbosense low-cost sensor network.

scholarly journals Integration and calibration of NDIR CO<sub>2</sub> low-cost sensors, and their operation in a sensor network covering Switzerland

2019 ◽  
Author(s):  
Michael Mueller ◽  
Peter Graf ◽  
Jonas Meyer ◽  
Anastasia Pentina ◽  
Brunner Dominik ◽  
...  
Keyword(s):  
Data Processing ◽  
Sensor Network ◽  
Low Cost ◽  
Significant Loss ◽  
Sensor Calibration ◽  
Data Filtering ◽  
Ambient Conditions ◽  
Term Operation ◽  
Reference Instrument

Abstract. More than 300 LP8 CO2 sensors were integrated into sensor units and evaluated for the purpose of long-term operation in the Carbosense CO2 sensor network in Switzerland. Prior to deployment, all sensors were calibrated in a pressure and climate chamber, and in ambient conditions co-located with a reference instrument. To investigate their long-term performance and to test different data processing strategies, 18 sensors were deployed at five locations equipped with a reference instrument after calibration. Their accuracy during 19 to 25 months deployment was between 8 to 12 ppm. This level of accuracy requires careful sensor calibration prior to deployment, continuous monitoring of the sensors, efficient data filtering, and a procedure to correct drifts and jumps in the sensor signal during operation. High relative humidity (> ∼85 %) impairs the LP8 measurements, and corresponding data filtering results in a significant loss during humid conditions. The LP8 sensors are not suitable for the detection of small regional gradients and long-term trends. However, with careful data processing, the sensors are able to resolve CO2 changes and differences with a magnitude larger than about 20 ppm. Thereby, the sensor can resolve the site-specific CO2 signal at most locations in Switzerland. A low power network (LPN) using LoRaWAN allowed reliable data transmission with low energy consumption, and proved to be a key element of the Carbosense low-cost sensor network.

scholarly journals Genotype-Dependent Tipburn Severity During Lettuce Hydroponic Culture Is Associated with Altered Nutrient Leaf Content

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 616
Author(s):  
Virginia Birlanga ◽  
José Ramón Acosta-Motos ◽  
José Manuel Pérez-Pérez
Keyword(s):  
Low Cost ◽  
Nutrient Content ◽  
Leafy Vegetables ◽  
Production Methods ◽  
Growing Seasons ◽  
Lactuca Sativa L ◽  
Hydroponic Cultivation ◽  
Highly Correlated ◽  
Nutrient Solutions ◽  
Nutrient Traits

Cultivated lettuce (Lactuca sativa L.) is one of the most important leafy vegetables in the world, and most of the production is concentrated in the Mediterranean Basin. Hydroponics has been successfully utilized for lettuce cultivation, which could contribute to the diversification of production methods and the reduction of water consumption and excessive fertilization. We devised a low-cost procedure for closed hydroponic cultivation and easy phenotyping of root and shoot attributes of lettuce. We studied 12 lettuce genotypes of the crisphead and oak-leaf subtypes, which differed on their tipburn resistance, for three growing seasons (Fall, Winter, and Spring). We found interesting genotype × environment (G × E) interactions for some of the studied traits during early growth. By analyzing tipburn incidence and leaf nutrient content, we were able to identify a number of nutrient traits that were highly correlated with cultivar- and genotype-dependent tipburn. Our experimental setup will allow evaluating different lettuce genotypes in defined nutrient solutions to select for tipburn-tolerant and highly productive genotypes that are suitable for hydroponics.

scholarly journals Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

2019 ◽  
Author(s):  
Leigh R. Crilley ◽  
Ajit Singh ◽  
Louisa J. Kramer ◽  
Marvin D. Shaw ◽  
Mohammed S. Alam ◽  
...  
Keyword(s):  
Correction Factor ◽  
Low Cost ◽  
Particle Mass ◽  
Ambient Atmosphere ◽  
Correction Factors ◽  
Aerosol Composition ◽  
Kohler Theory ◽  
Suitable Reference ◽  
Aerosol Hygroscopicity ◽  
Mass Concentrations

Abstract. There is considerable interest in using low-cost optical particle counters (OPC) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data needs to be cross-comparable with particle mass reference instrumentation, and as yet, there is no widely agreed methodology. Aerosol hygroscopicity is known to be a key parameter to consider when correcting particle mass concentrations derived from a low-cost OPC, particularly at high ambient Relative Humidity (RH). Correction factors have been developed that apply κ-Köhler theory to correct for the influence of water uptake by hygroscopic aerosols. We have used datasets of co-located reference particle measurements and a low-cost OPC (OPC-N2, Alphasense), collected in four cities in three continents, to explore the performance of this correction factor. We report evidence that the elevated particle mass concentrations, reported by the low-cost OPC relative to reference instrumentation, is due to bulk aerosol hygroscopicity under different RH conditions, which is determined by aerosol composition and in particular the levels of hygroscopic aerosols (sulphate and nitrate). We exploit measurements made in volcanic plumes in Nicaragua, that are predominantly composed of sulphate aerosol, as a natural experiment to demonstrate this behaviour in the ambient atmosphere, with the observed humidogram closely resembling the calculated pure sulphuric acid humidogram. The results indicate that the particle mass concentrations derived from low-cost OPCs during periods of high RH (> 60 %) need to be corrected for aerosol hygroscopic growth. We employed a correction factor based on κ-Köhler theory and observed corrected OPC-N2 PM2.5 mass concentrations to be within 33 % of reference measurements at all sites. The results indicated that an in situ derived κ (using suitable reference instrumentation) would lead to the most accurate correction relative to co-located reference instruments. Applying literature κ in the correction factor also resulted in improved performance of OPC-N2, to be within 50 % of reference. Therefore, for areas where suitable reference instrumentation for developing a local correction factor is lacking, using a literature κ value can result in a reasonable correction. For locations with low levels of hygroscopic aerosols and RH, a simple calibration against gravimetric measurements (using suitable reference instrumentation) would likely be sufficient. Whilst this study generated correction factors specific for the Alphasense OPC-N2 sensor, the calibration methodology developed is likely amenable to other low cost PM sensors.

scholarly journals Measurement report: The chemical composition of and temporal variability in aerosol particles at Tuktoyaktuk, Canada, during the Year of Polar Prediction Second Special Observing Period

2021 ◽  
Vol 21 (18) ◽  
pp. 14199-14213
Author(s):  
John MacInnis ◽  
Jai Prakash Chaubey ◽  
Crystal Weagle ◽  
David Atkinson ◽  
Rachel Ying-Wen Chang
Keyword(s):  
Air Quality ◽  
Chemical Composition ◽  
Aerosol Particles ◽  
Road Dust ◽  
Quality Standard ◽  
The Arctic ◽  
Similar Range ◽  
The Government ◽  
Government Of Canada ◽  
Mass Concentrations

Abstract. The chemical composition, sources, and concentrations of aerosol particles vary on a seasonal basis in the Arctic. While existing research has focused on understanding the occurrence of aerosol particles during the Arctic winter and spring, less is known of their occurrence during the Arctic summer. In this study, atmospheric aerosol particle chemical composition and concentration were determined during July–September 2018 at Tuktoyaktuk, NT, Canada (69.4∘ N, 133.0∘ W), to coincide with the Year of Polar Prediction's Second Special Observing Period in the Arctic. The chemical composition of fine (PM2.5) and coarse (PM10–2.5) aerosol filter samples suggests the ocean, mineral and/or road dust, and combustion were sources of the sampled aerosol particles. Mass concentrations of PM2 and PM10, estimated from optical particle counter measurements, remained within a similar range during the study. However, elevated mass concentrations coincided with a festival in the community of Tuktoyaktuk, suggesting local human activity was an important source of aerosol particles. Mass concentrations of PM2, which promote negative health effects in humans, were significantly lower at Tuktoyaktuk than the national air quality standard recommended by the government of Canada. These measurements provide an important baseline to compare with future measurements associated with the assessment of aerosol chemistry and air quality in the Arctic.

A simple and low-cost method for leaf area measurement of detached leaves

1997 ◽  
Vol 33 (01) ◽  
pp. 65-72 ◽  
Author(s):  
J. T. Korva ◽  
G. A. Forbes
Keyword(s):  
Solanum Tuberosum ◽  
Leaf Area ◽  
Low Cost ◽  
Electronic Equipment ◽  
New Method ◽  
Area Measurement ◽  
Water Spray ◽  
Spray Method ◽  
Detached Leaves ◽  
Highly Correlated

A technique for leaf area measurement utilizing water spray as an inexpensive substitute for electronic equipment was developed and tested with leaves of potato (Solanum tuberosum L.). The leaf areas measured by the spray method were highly correlated with those measured by an electronic area meter. Measurements of leaf area obtained by the spray method were significantly more highly correlated with those obtained by the area meter than were the measurements of dry weights. The main advantages of the new method are precision, accuracy and immediate results at a low cost.

scholarly journals Laboratory evaluation of a low-cost, real-time, aerosol multi-sensor

2018 ◽  
Vol 15 (7) ◽  
pp. 559-567 ◽  
Author(s):  
Robert J. Vercellino ◽  
Darrah K. Sleeth ◽  
Rodney G. Handy ◽  
Kyeong T. Min ◽  
Scott C. Collingwood
Keyword(s):  
Real Time ◽  
Low Cost ◽  
Laboratory Evaluation

The Correcting Approach of Gyroscope-Free Inertial Navigation Based on the Applicable Topological Map

2019 ◽  
Vol 19 (2) ◽  
Author(s):  
Mehdi Dehghani ◽  
Hamed Kharrati ◽  
Hadi Seyedarabi ◽  
Mahdi Baradarannia
Keyword(s):  
Mobile Robot ◽  
Mobile Robots ◽  
Inertial Sensors ◽  
Low Cost ◽  
Measurement Unit ◽  
Sensor Calibration ◽  
Topological Map ◽  
Stereo Cameras ◽  
Long Time ◽  
Navigation Errors

The accumulated error and noise sensitivity are the two common problems of ordinary inertial sensors. An accurate gyroscope is too expensive, which is not normally applicable in low-cost missions of mobile robots. Since the accelerometers are rather cheaper than similar types of gyroscopes, using redundant accelerometers could be considered as an alternative. This mechanism is called gyroscope-free navigation. The article deals with autonomous mobile robot (AMR) navigation based on gyroscope-free method. In this research, the navigation errors of the gyroscope-free method in long-time missions are demonstrated. To compensate the position error, the aid information of low-cost stereo cameras and a topological map of the workspace are employed in the navigation system. After precise sensor calibration, an amendment algorithm is presented to fuse the measurement of gyroscope-free inertial measurement unit (GFIMU) and stereo camera observations. The advantages and comparisons of vision aid navigation and gyroscope-free navigation of mobile robots will be also discussed. The experimental results show the increasing accuracy in vision-aid navigation of mobile robot.

scholarly journals Evaluation of an Easy-to-Install, Low-Cost Dendrometer Band for Citizen-Science Tree Research

2019 ◽  
Vol 117 (4) ◽  
pp. 317-322
Author(s):  
Michael G Just ◽  
Steven D Frank
Keyword(s):  
Citizen Science ◽  
Urban Areas ◽  
Large Scale ◽  
Low Cost ◽  
Acer Rubrum ◽  
Cost Effective ◽  
Stem Growth ◽  
Growth Monitoring ◽  
Eastern United States ◽  
Highly Correlated

AbstractTree-stem growth is an important metric for evaluating many ecological and silvicultural research questions. However, answering these questions may require monitoring growth on many individual trees that span changing environments and geographies, which can incur significant costs. Recently, citizen science has been successfully employed as a cost-effective approach to collect data for large-scale projects that also increases scientific awareness. Still, citizen-science-led tree-growth monitoring requires the use of tools that are affordable, understandable, and accurate. Here, we compare an inexpensive, easy-to-install dendrometer band to two other bands that are more expensive with more complex installations. We installed a series of three dendrometers on 31 red maples (Acer rubrum) in two urban areas in the eastern United States. We found that the stem-growth measurements reported by these dendrometers were highly correlated and, thus, validate the utility of the inexpensive band.

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