Technical Evaluation of Sensor Technology (TEST) Program
Clarity Node Sensor
2018 – 1st Quarter
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
2
Introduction and Sensor Profile
This analysis report is focused on assessing the performance of the Clarity Node sensor as a part
of the District’s Technical Evaluation of Sensor Technology (TEST) Program. The Clarity sensor
uses optical laser-based particle counting methodology to estimate the concentration of PM2.5.
The Clarity sensor also measures CO2, NO2, Total VOCs, temperature, and relative humidity
within a solar powered box. A unique feature of the Clarity Node sensor is its ability to self-
correct its PM2.5 estimates based on real-time regulatory monitor readings in the area. This self-
calibration process is aimed to result in more accurate PM2.5 measurements from the Clarity
Node sensors, making them a more viable option for various monitoring projects.
Background and Approach of Evaluation Test
In late 2017, the Clarity Movement Company approached the District regarding the testing of
their Clarity Node sensors in the conditions of the San Joaquin Valley. After coordination on
where the sensors could be placed in the District’s network for testing, on February 28, 2018, 5
Clarity sensors were installed and started collecting data to compare the performance of Clarity
sensors to regulatory PM2.5 analyzers. Clarity Node sensors were installed at the District air
monitoring stations of Clovis-Villa, Manteca, Merced-Coffee, Tracy-Airport, and Tranquillity. The
data sets from each station compare Clarity sensor PM2.5 data to that of the regulatory PM2.5
data that is collocated at each of the District sites. The scatter plots and time series graphs below
show how the datasets compare for both hourly values and the 24-hour average.
Overview of Analysis Findings from Current Period
The analysis for this report covers the time period of March 1, 2018, through March 31, 2018
(2018 – 1st quarter). The month of March 2018 had fairly good dispersion conditions with low to
moderate PM readings throughout the Valley. Several low pressure systems moved through the
Valley, which helped keep dispersion conditions positive for air quality through this time period.
Recorded PM2.5 concentrations for both the Clarity Node sensor and regulatory monitors were
low through the month of March. This assessment compares the Clarity Node performance
against two different regulatory PM2.5 monitors operating in the District’s network – the
MetOne BAM and the Teledyne 602. Overall, most of the Clarity Node sensors operating during
this period showed a slight high bias over the regulatory monitors, except for the Tranquillity
sensor, which shows a low bias. No significant events related to air pollution occurred during
March 2018.
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
3
Site Specific Analysis of Clarity-Node Sensor Performance
Clovis-Villa
For the 24-hour average, Clarity data had a 0.9 µg/m3 high bias during the month of March 2018.
For the hourly average, Clarity data had a 0.8 µg/m3 high bias over the same period.
y = 0.7456x + 2.2357
R² = 0.7522
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Cla
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Teledyne 602 FEM
Clovis 24-hour Average Comparison
y = 0.4832x + 3.7535
R² = 0.39510
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Cla
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Teledyne 602 FEM
Clovis Hourly Average Comparison
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(µµ µµ
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Clovis 24-hour average FEM v. Clarity
Clovis - Clarity Clovis - FEM
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
4
Manteca
For the 24-hour average, Clarity data had a 2.4 µg/m3 high bias during the month of March 2018.
For the hourly average, Clarity data had a 2.4 µg/m3 high bias over the same period.
y = 1.2217x + 0.957
R² = 0.71510
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Cla
rity
Teledyne 602 FEM
Manteca 24-hour Average Comparison
y = 0.8389x + 3.4437
R² = 0.43770
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Teledyne 602 FEM
Manteca Hourly Average Comparison
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Manteca 24-hour average FEM v. Clarity
Manteca - Clarity Manteca - FEM
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
5
Merced-Coffee
For the 24-hour average, Clarity data had a 2.2 µg/m3 high bias during the month of March 2018.
For the hourly average, Clarity data had a 2.2 µg/m3 high bias over the same period.
y = 1.208x + 0.8974
R² = 0.54170
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Cla
rity
MetOne BAM FEM
Merced 24-hour Average Comparison
y = 0.8773x + 3.011
R² = 0.38470
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MetOne BAM FEM
Merced Hourly Average Comparison
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(µµ µµ
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Merced 24-hour average FEM v. Clarity
Merced - Clarity Merced - FEM
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
6
Tracy-Airport
For the 24-hour average, Clarity data had a 2.2 µg/m3 high bias from March 1 to 22, 2018. For
the hourly average, Clarity data had a 2.2 µg/m3 high bias over the same period. Data from the
Tracy MetOne BAM monitor was not available from March 23 through the end of the month due
to the analyzer undergoing calibration.
y = 0.8873x + 2.5468
R² = 0.17940
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MetOne BAM FEM
Tracy 24-hour Average Comparison
y = 0.6262x + 3.2622
R² = 0.1158
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MetOne BAM FEM
Tracy Hourly Average Comparison
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(µµ µµ
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Tracy 24-hour average FEM v. Clarity
Tracy - Clarity Tracy - FEM
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
7
Tranquillity
For the 24-hour average, Clarity data had a 0.8 µg/m3 low bias during the month of March 2018.
For the hourly average, Clarity data had a 0.8 µg/m3 low bias over the same period.
y = 2.1362x - 7.0518
R² = 0.750
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Cla
rity
MetOne BAM FEM
Tranquillity 24-hour Average Comparison
y = 1.4686x - 3.3474
R² = 0.4253
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MetOne BAM FEM
Tranquillity Hourly Average Comparison
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Tranquillity 24-hour average FEM v. Clarity
Tranquillity - Clarity Tranquillity - FEM
San Joaquin Valley Air Pollution Control District Clarity Node Sensor
Technical Evaluation of Sensor Technology (TEST) Program 2018 – 1st Quarter
8
Statistical Summary
The following table provides a statistical summary of the data collected during the analysis period
of this report.
Statistic Clovis Manteca Merced Tracy Tranquillity
FEM Avg 5.6 6.5 6.4 2.7 5.5
Clarity Avg 6.4 8.9 8.6 4.4 4.8
FEM 1-hr Max 22.6 32.8 33.0 13.0 25.0
Clarity 1-hr Max 21.5 39.7 35.9 46.8 81.1
FEM 24-hr Max 12.4 14.4 11.7 7.5 12.4
Clarity 24-hr Max 12.8 22.4 22.8 18.1 27.0
1-hr R2 0.3951 0.4377 0.3847 0.1158 0.4253
1-hr Slope 0.4832 0.8389 0.8773 0.6262 1.4686
1-hr Intercept 3.7535 3.4437 3.0110 3.2622 -3.3474
24-hr R2 0.7522 0.7151 0.5417 0.1794 0.7500
24-hr Slope 0.7456 1.2217 1.2080 0.8873 2.1362
24-hr Intercept 2.2357 0.9570 0.8974 2.5468 -7.0518