Low-cost sensors Archives - Page 2 of 3

Low-cost research awareness meetings

Across two meetings, I met with institute and university staff and management to raise awareness for low-cost research opportunities. Over the past five years, both developing low-cost sensor systems and conducting research with students (student science) has given me access to many hours of data and some publications at little cost in the field of air pollution. I strongly believe that the same can be conducted in other fields.

At April 5, 2024, the meeting participants included lecturers and deans of the Arba Minch Water Technology Institute, as well as its scientific director (Dr. Bogale Gebremariam). With Dr. Tesfaye Habtemariam (Executive Director for Research of Arba Minch University) also joining us, we could have a fruitful discussion on opportunities and challenges with all layers of the university. This meeting was followed up with a meeting on April 11, 2024, where the university president (Dr. Damtew Darza), vice president of academics (Dr. Alemayehu Chufamo) and vice president of research (Behailu Merdekios) participated. Some of my students were present to show the instruments with which they conducted measurements. The locally developed soil-moisture sensor system was also on display.

Final year students of Water Supply and Environmental Engineering use locally assembled air pollution sensors.

The meetings raised awareness for low-cost research opportunities and integrating research with education. Below slides show the presentation and minutes of the challenges and solutions raised across the two meetings.

AirQo to host measurement data

AirQo has agreed to host our PM2.5 measurement data on their platform. AirQo started at Makere University (Uganda). It is currently the only builder of professional low-cost PM sensor systems in the African continent. I met them at the international conference “Together for cleaner air in Ethiopia” in Addis Ababa, December 2023. Their sensor systems provide real-time data, and this data is hosted on their platform. Over the past years, I have collected data at some locations in Arba Minch, and the coming year I plan to install fixed locations. Possibly I will include real-time data transmission on those measurement systems. However, AirQo also agreed to host historical data, based on CSV files I submit to them.

As a sample, I submitted historical data collected between April – May 2021. You can download it by visiting www.analytics.airqo.net. This proof of concept shows the future opportunity of locally constructing sensor systems in Arba Minch, installing them across Ethiopia, and openly sharing the data.

Successful import of components for fifty PM2.5 sensors

I am glad to share the successful import of components for fifty PM2.5 sensor systems. For the low-cost sensor systems, most items are available in Addis Ababa – but for a much higher price due to import restrictions. Last month, fifty pieces of all components were ordered in The Netherlands, and I was able to bring all these items into Ethiopia. For total costs of 2500 euro, and additionally 90,000 ETB of import tax, we have enough materials to construct more than fifty new measurement instruments. Considering that all measurements up to now have been conducted with approximately twenty systems, this is a huge increase of the measurement capacity.

Suitcase with materials for more than fifty sensors

A list of all materials, with links to the sellers:

Donation of sensors for collaboration with Debre Birhan and Addis Ababa

Professor Solomon Bililign of the North Carolina Agricultural and Technical State University has made a donation of 30 SPS30 Sensirion sensors to Addis Ababa University, Arba Minch University and Debre Berhan University. With these sensors as input, teams at Addis Ababa University and Debre Berhan University can start building sensor systems following my designs (and hopefully improving on it).

In December 2023 I presented my work on low-cost sensor system development and student science at the ‘Together for cleaner air in Ethiopia’ international conference in Addis Ababa. Based on this, Professor Solomon decided to fund components for additional sensor systems. The Sensirion SPS30 is not available in Ethiopia, and is therefore the primary candidate for funding. All other components, albeit at higher prices, are available in Ethiopia. The university teams will provide those components themselves.

Low cost soil moisture sensor

A team of Arba Minch Water Technology Institute (AWTI) has assembled a soil moisture sensor system with arduino and micro-electronics. Last summer, I was able to bring five soil moisture capacitance sensors from The Netherlands. Demiso Daba, Tafesse Fitensa and Getachew Enssa followed the one-day Arduino workshop. A PhD student (Edmealem Temesgen) and MSc student (Chanako Dane) from the faculty of Irrigation became also involved, as the availability of measurement instruments makes it possible for them to collect primary data for their research.

Field installation

Field measurements

Soil moisture system inside

Soil moisture system outside

As part of his PhD study, Edmealem Temesgen conducts field comparisons between the sensor system and the laboratory volumetric method for soil moisture tests. The first results are very promising, see below figure.

Preliminary results of a comparison between volumetric method and sensor system soil moisture field measurements. Results currently under publication.

Article on road-side measurements

The Ethiopian Journal of Water Science and Technology (EJWST) has published an article by me and my students titled “Roadside PM2.5 concentrations measured with low-cost sensors and student science in Arba Minch, Ethiopia“. During April and May 2022, students of Water Supply and Environmental Engineering, year 3, conducted PM2.5 measurements at road-side locations. They did so with the locally assembled sensor system, as part of the course Air and Noise pollution. In this way, seven groups of 5-6 students collected approximately 2,500 hours of PM2.5 data. After the course, I analyzed the data and turned it into a manuscript. Two of the students (Mekdes Dawit and Tewodros Zerihun) provided valuable feedback and became co-authors to the article.

Students conducted measurements at six locations: four stationary and two mobile locations (Figure 1 in the article).

Measurements were conducted at six locations: one at the university campus gate, two at busy squares, one at the bus station, and two inside public transport tuktuks (bajaj). Except for the campus gate, at all locations concentrations exceeded WHO guideline values. Highest concentrations were observed during the morning period at the bus station. Supporting data and data processing code is shared on an OSF repository.

PM2.5 concentrations measured at six locations, in contrast with the WHO guideline (Figure 3 in the article).

Low-cost sensors and student science

The article is a showcase of the application of both locally assembled low-cost sensors and student science. Combined, these methods provided me with a lot of data for very little costs. At the same time it provided my students with practical experience as part of a course. During the course Air and Noise pollution, they got lectures on the course contents. They had to apply this knowledge by selecting a specific research question, constructing measurement plans, installing and operating the instruments, processing the data in Microsoft Excel, and writing a report.

Article on low-cost sensor system

Over the past four years, I have built a low-cost particulate matter (PM) sensor system from scratch, and tested it under various situations in Ethiopia. Together with Afework Tademe, a colleague from Electrical and Computer Engineering, I have written an article on this low-cost sensor system, which is now published by the Clean Air Journal.

One of the locally assembled low-cost particulate matter sensor systems.

The publication covers use of the sensor system across fourteen locations for more than 30,000 hours combined. In the publication, we openly share the system design. All data and materials supporting the publication are available in an OSF repository. We also show results of data quality validations. These validations included collocation of multiple sensors and gravimetric measurements.

It is not our intent to create and share the best sensor system. Rather, we want to show that a sensor system can be built locally, with two main benefits: lower costs and local experience training. Furthermore, we fill a gap in local validation of low-cost sensors. Several types of low-cost sensors are being used on the African continent. However, field validation under circumstances common to a country like Ethiopia are extremely limited. Up to my knowledge, we are the first to share validation of the Sensirion SPS30 with gravimetric measurements under high concentrations (inside kitchens with biomass fuel) and ambient concentrations in Ethiopia – or even Africa. Or, more correctly, we fill part of the gap. I want to add (much) more validation measurements. Some of this is ongoing. Currently, an MSc student compares my sensor systems with gravimetric measurements in Addis Ababa and Adama.

International conference air quality Addis Ababa

Lund university (Sweden), Haramaya University, Institutes of Geophysics, Space Science and Astronomy of Addis Ababa University, and the Department of Physics of North Carolina A&T State University co-organized the international conference ‘Together for cleaner air in Ethiopia’ (18-20 December 2023). I was offered the opportunity to give two presentations about the work at Arba Minch University: locally developing the low-cost sensor system, and conducting research with students (student science).

Participants of the ‘Together for cleaner air in Ethiopia’ workshop

Slides of the low-cost sensor system presentation:

Slides of the student science presentation:

Seminar on low-cost research

Research budget in Ethiopia is extremely limited, and many of my colleagues are not involved in research due to that. The Water Resources Research Centre organized a seminar on conducting low-cost research at December 4, 2023. I presented from own experience on ‘How to collect +25,000 hours of data and create five scientific articles with almost no budget’. This included sharing my work on low-cost sensor development and conducting research with students. After presenting my experiences, we had an interactive session with the twenty attendants on what opportunities and challenges there are for low-cost research.

Validation measurements in Addis Ababa and Adama

Wegene Negese, an MSc student at Arba Minch University (Climate) and employee of the Ethiopian Meteorology Institute (EMI), has conducted validation measurements of the low-cost sensor system with SPS30 Sensirion at the EMI meteorological stations of Addis Ababa and Adama. For a period of four months, he collocated the sensor system with itself, and conducted gravimetry measurements. Gravimetry is the reference method for calibrating PM2.5 measurement instruments.

Sensors were installed at meteorology stations of Addis Ababa and Adama

He is currently working on his MSc thesis, but I can already present some preliminary results:

The coefficient of variation (CV; a measure of variation between two identical instruments) was 9.5% for two sensor systems in Addis Ababa (based on 12,677 10-minute averages), and 4.4% for two sensor systems in Adama (based on 4,135 10-minute averages). This indicates that the variation between two sensor systems is lower than 10%. 10% is set as a maximum allowed CV for measurement instruments by the NIOSH and the US EPA.
The sensor system systematically measures lower than gravimetry, but the correlation is strong. Linear regression of all data points of Addis Ababa and Adama combined (n=16) leads to a slope of 1.62 with an R2 of 0.99. The Pearson correlation is 0.97.

The data of Wegene confirms wat I found in earlier data with measurements in Arba Minch: the SPS30 Sensirion has low within-variation, and shows a stable bias both under ambient and indoor (high) concentration settings versus gravimetry measurements (see this publication). In other words: the SPS30 Sensirion appears to be a very good sensor under Ethiopian circumstances.