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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Teledyne 602 FEM

Clovis 24-hour Average Comparison

y = 0.4832x + 3.7535

R² = 0.39510

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Teledyne 602 FEM

Clovis Hourly Average Comparison

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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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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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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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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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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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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