{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,10]],"date-time":"2026-05-10T15:23:23Z","timestamp":1778426603163,"version":"3.51.4"},"reference-count":36,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2024,6,25]],"date-time":"2024-06-25T00:00:00Z","timestamp":1719273600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000780","name":"EU Horizon Europe","doi-asserted-by":"publisher","award":["101057271"],"award-info":[{"award-number":["101057271"]}],"id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper addresses the challenges of calibrating low-cost electrochemical sensor systems for air quality monitoring. The proliferation of pollutants in the atmosphere necessitates efficient monitoring systems, and low-cost sensors offer a promising solution. However, issues such as drift, cross-sensitivity, and inter-unit consistency have raised concerns about their accuracy and reliability. The study explores the following three calibration methods for converting sensor signals to concentration measurements: utilizing manufacturer-provided equations, incorporating machine learning (ML) algorithms, and directly applying ML to voltage signals. Experiments were performed in three urban sites in Greece. High-end instrumentation provided the reference concentrations for training and evaluation of the model. The results reveal that utilizing voltage signals instead of the manufacturer\u2019s calibration equations diminishes variability among identical sensors. Moreover, the latter approach enhances calibration efficiency for CO, NO, NO2, and O3 sensors while incorporating voltage signals from all sensors in the ML algorithm, taking advantage of cross-sensitivity to improve calibration performance. The Random Forest ML algorithm is a promising solution for calibrating similar devices for use in urban areas.<\/jats:p>","DOI":"10.3390\/s24134110","type":"journal-article","created":{"date-parts":[[2024,6,26]],"date-time":"2024-06-26T09:29:33Z","timestamp":1719394173000},"page":"4110","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Calibration and Inter-Unit Consistency Assessment of an Electrochemical Sensor System Using Machine Learning"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6439-9282","authenticated-orcid":false,"given":"Ioannis D.","family":"Apostolopoulos","sequence":"first","affiliation":[{"name":"Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology Hellas (FORTH), 26504 Patras, Greece"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5808-7776","authenticated-orcid":false,"given":"Silas","family":"Androulakis","sequence":"additional","affiliation":[{"name":"Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology Hellas (FORTH), 26504 Patras, Greece"},{"name":"Department of Chemical Engineering, University of Patras, 26504 Patras, Greece"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7295-8723","authenticated-orcid":false,"given":"Panayiotis","family":"Kalkavouras","sequence":"additional","affiliation":[{"name":"Institute for Environmental Research & Sustainable Development, National Observatory of Athens, 11810 Athens, Greece"},{"name":"Department of Environment, University of the Aegean, 81400 Mytilene, Greece"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3630-4121","authenticated-orcid":false,"given":"George","family":"Fouskas","sequence":"additional","affiliation":[{"name":"Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology Hellas (FORTH), 26504 Patras, Greece"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8085-9795","authenticated-orcid":false,"given":"Spyros N.","family":"Pandis","sequence":"additional","affiliation":[{"name":"Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology Hellas (FORTH), 26504 Patras, Greece"},{"name":"Department of Chemical Engineering, University of Patras, 26504 Patras, Greece"}]}],"member":"1968","published-online":{"date-parts":[[2024,6,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"24815","DOI":"10.1007\/s11356-020-09042-2","article-title":"Ambient Air Pollution and Its Influence on Human Health and Welfare: An Overview","volume":"27","author":"Almetwally","year":"2020","journal-title":"Environ. 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