{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T15:16:01Z","timestamp":1775229361345,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2021,7,3]],"date-time":"2021-07-03T00:00:00Z","timestamp":1625270400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006182","name":"Funda\u00e7\u00e3o de Amparo \u00e0 Pesquisa e Inova\u00e7\u00e3o do Esp\u00edrito Santo","doi-asserted-by":"publisher","award":["88336650"],"award-info":[{"award-number":["88336650"]}],"id":[{"id":"10.13039\/501100006182","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004225","name":"Petrobras","doi-asserted-by":"publisher","award":["2017\/00702-6"],"award-info":[{"award-number":["2017\/00702-6"]}],"id":[{"id":"10.13039\/501100004225","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["CEECIND\/00034\/2018"],"award-info":[{"award-number":["CEECIND\/00034\/2018"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UIDB\/50025\/2020"],"award-info":[{"award-number":["UIDB\/50025\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UIDP\/50025\/2020"],"award-info":[{"award-number":["UIDP\/50025\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper proposed a liquid level measurement and classification system based on a fiber Bragg grating (FBG) temperature sensor array. For the oil classification, the fluids were dichotomized into oil and nonoil, i.e., water and emulsion. Due to the low variability of the classes, the random forest (RF) algorithm was chosen for the classification. Three different fluids, namely water, mineral oil, and silicone oil (Kryo 51), were identified by three FBGs located at 21.5 cm, 10.5 cm, and 3 cm from the bottom. The fluids were heated by a Peltier device placed at the bottom of the beaker and maintained at a temperature of 318.15 K during the entire experiment. The fluid identification by the RF algorithm achieved an accuracy of 100%. An average root mean squared error (RMSE) of 0.2603 cm, with a maximum RMSE lower than 0.4 cm, was obtained in the fluid level measurement also using the RF algorithm. Thus, the proposed method is a feasible tool for fluid identification and level estimation under temperature variation conditions and provides important benefits in practical applications due to its easy assembly and straightforward operation.<\/jats:p>","DOI":"10.3390\/s21134568","type":"journal-article","created":{"date-parts":[[2021,7,4]],"date-time":"2021-07-04T22:35:22Z","timestamp":1625438122000},"page":"4568","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":42,"title":["FBG-Based Temperature Sensors for Liquid Identification and Liquid Level Estimation via Random Forest"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8585-5603","authenticated-orcid":false,"given":"Katiuski","family":"Pereira","sequence":"first","affiliation":[{"name":"Graduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), Vit\u00f3ria 29075-910, ES, Brazil"}]},{"given":"Wagner","family":"Coimbra","sequence":"additional","affiliation":[{"name":"Graduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), Vit\u00f3ria 29075-910, ES, Brazil"}]},{"given":"Renan","family":"Lazaro","sequence":"additional","affiliation":[{"name":"Graduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), Vit\u00f3ria 29075-910, ES, Brazil"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0687-3967","authenticated-orcid":false,"given":"Anselmo","family":"Frizera-Neto","sequence":"additional","affiliation":[{"name":"Graduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), Vit\u00f3ria 29075-910, ES, Brazil"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8596-5092","authenticated-orcid":false,"given":"Carlos","family":"Marques","sequence":"additional","affiliation":[{"name":"Physics Department & I3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9075-0619","authenticated-orcid":false,"given":"Arnaldo Gomes","family":"Leal-Junior","sequence":"additional","affiliation":[{"name":"Graduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), Vit\u00f3ria 29075-910, ES, Brazil"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1016\/j.yofte.2017.11.006","article-title":"Multi-interface level in oil tanks and applications of optical fiber sensors","volume":"40","author":"Marques","year":"2018","journal-title":"Opt. 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