{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T03:45:57Z","timestamp":1775533557276,"version":"3.50.1"},"reference-count":46,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2021,12,8]],"date-time":"2021-12-08T00:00:00Z","timestamp":1638921600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This work reports the results of a study on the behaviour of five sensors recently developed for oil conditions monitoring, installed in-line in an experimental test rig for lubricants. The tests were carried out on seven oils of different origins (one synthetic ester, two bio-based synthetic esters, four vegetable oils) and use (two UTTOs and five hydraulic oils), under controlled working conditions, according to a specially designed test method. At first, the study concerned the identification of the conditions for the correct sensors\u2019 installation. Then, the tests started applying to the fluids severe work cycles intended to accelerate oil ageing. The data of viscosity, permittivity, relative humidity, electric conductivity, particle contamination, and ferro-magnetic particles provided by the sensors were compared to the results of laboratory analyses made on oil samples taken during the tests with the aim of verifying the sensors measurements accuracy and reliability and selecting the more suitable ones to in-line oil conditions monitoring, in the perspective of introducing them also in field applications, e.g., on agricultural tractors, for preventing damages due to oil deterioration, and in managing the machine maintenance.<\/jats:p>","DOI":"10.3390\/s21248201","type":"journal-article","created":{"date-parts":[[2021,12,8]],"date-time":"2021-12-08T23:30:00Z","timestamp":1639006200000},"page":"8201","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Bench Testing of Sensors Utilized for In-Line Monitoring of Lubricants and Hydraulic Fluids Properties"],"prefix":"10.3390","volume":"21","author":[{"given":"Daniele","family":"Pochi","sequence":"first","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Renato","family":"Grilli","sequence":"additional","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Laura","family":"Fornaciari","sequence":"additional","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Monica","family":"Betto","sequence":"additional","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Stefano","family":"Benigni","sequence":"additional","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Roberto","family":"Fanigliulo","sequence":"additional","affiliation":[{"name":"Consiglio per la ricerca in agricoltura e l\u2019analisi dell\u2019economia agraria (CREA), Centro di ricerca Ingegneria e Trasformazioni agroalimentari (Research Centre for Engineering and Agro-Food Processing), Via Della Pascolare 16, 00015 Monterotondo, Rome, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"21","DOI":"10.3989\/gya.000111","article-title":"Vegetable oil basestocks for lubricants","volume":"62","author":"Salas","year":"2011","journal-title":"Grasas Aceites"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.ejpe.2016.03.003","article-title":"Manufacturing of environment friendly biolubricants from vegetable oils","volume":"26","author":"Heikal","year":"2017","journal-title":"Egypt. J. Petrol."},{"key":"ref_3","first-page":"587","article-title":"Review on vegetable oil as bio lubricant","volume":"5","author":"Ashish","year":"2017","journal-title":"Int. J. Sci. Res. Dev."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Fanigliulo, R., Pochi, D., Bondioli, P., Grilli, R., Fornaciari, L., Folegatti, L., Malaguti, L., Matteo, R., Ugolini, L., and Lazzeri, L. (2021). Semi-refined Crambe abyssinica (Hochst. EX R.E.Fr.) Oil as Biobased Hydraulic Fluid for Agricultural Applications. Biomass Convers. Biorefin., 1\u201313.","DOI":"10.1007\/s13399-020-01213-y"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2100116","DOI":"10.1002\/ejlt.202100116","article-title":"Bench Test of a Hydraulic Biofluid Based on Refined Pomace Oil","volume":"123","author":"Fanigliulo","year":"2021","journal-title":"Eur. J. Lipid Sci. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"79","DOI":"10.13031\/aea.13488","article-title":"Vegetable-based Oil as UTTO Fluid for Agricultural Tractors Application","volume":"36","author":"Pochi","year":"2020","journal-title":"Appl. Eng. Agric."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1973","DOI":"10.1088\/0957-0233\/14\/11\/015","article-title":"An Integrated On-line Oil Analysis Method for Condition Monitoring","volume":"14","author":"Yonghui","year":"2003","journal-title":"Meas. Sci. Technol."},{"key":"ref_8","first-page":"124","article-title":"Lubrication Oil Condition Monitoring and Remaining Useful Life Prediction with Particle Filtering","volume":"4","author":"Zhu","year":"2013","journal-title":"Int. J. Progn. Health Manag."},{"key":"ref_9","first-page":"297","article-title":"Literature Review of Machine Condition Monitoring with Oil Sensors -Types of Sensors and Their Functions","volume":"36","author":"Hong","year":"2020","journal-title":"Tribol. Lubr."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1108\/00368799910268066","article-title":"Oil Analysis Cost-effective Machine Condition Monitoring Technique","volume":"51","author":"Newell","year":"1999","journal-title":"Ind. Lubr. Tribol."},{"key":"ref_11","first-page":"229","article-title":"Tribological properties of biodegradable universal tractor transmission oil","volume":"38","author":"Kolb","year":"2016","journal-title":"Tribol. Ind."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"29","DOI":"10.3989\/gya.056210","article-title":"Vegetable Oils as Hydraulic Fluids for Agricultural Applications","volume":"62","author":"Mendoza","year":"2011","journal-title":"Grasas Aceites"},{"key":"ref_13","first-page":"150","article-title":"Synthesis of Biolubricants with High Viscosity and High Oxidation Stability","volume":"10","author":"Bondioli","year":"2002","journal-title":"OCL Oilseeds Fats Crop. Lipids"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"417","DOI":"10.5545\/sv-jme.2013.1451","article-title":"Analysis of the Influence of Contaminants on the Biodegradability Characteristics and Ageing of Biodegradable Hydraulic Fluids","volume":"60","author":"Asaff","year":"2014","journal-title":"Stroj. Vestn. J. Mech. Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"292","DOI":"10.1016\/j.indcrop.2006.06.008","article-title":"Oxidation and Low Temperature Stability of Vegetable Oil-based Lubricants","volume":"2","author":"Erhan","year":"2006","journal-title":"Ind. Crops Prod."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.sna.2005.02.024","article-title":"Viscosity Sensors for Engine Oil Condition Monitoring\u2014Application and Interpretation of Results","volume":"121","author":"Agoston","year":"2005","journal-title":"Sens. Actuators A"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"433","DOI":"10.3103\/S106836661006005X","article-title":"Online Monitoring of the Viscosity of Lubricating Oils","volume":"31","author":"Markova","year":"2010","journal-title":"J. Frict. Wear"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.sna.2003.08.005","article-title":"Physical Sensors for Water-in-oil Emulsions","volume":"110","author":"Jakoby","year":"2004","journal-title":"Sens. Actuators A"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1270","DOI":"10.1016\/S0043-1648(03)00175-3","article-title":"Wear Monitoring Based on the Analysis of Lubricant Contamination by Optical Ferroanalyzer","volume":"255","author":"Myshkin","year":"2003","journal-title":"Wear"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1177\/0142331208092026","article-title":"A Particle-filtering Approach for On-line Fault Diagnosis and Failure Prognosis","volume":"31","author":"Orchard","year":"2011","journal-title":"Trans. Inst. Meas. Control"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1205","DOI":"10.11118\/actaun201765041205","article-title":"Effect of contaminants on the lifetime of hydraulic biooils and systems","volume":"65","author":"Machal","year":"2017","journal-title":"Acta Univ. Agric. Silvic. Mendel. Brun."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1016\/S0925-4005(02)00155-7","article-title":"Engine Oil Condition Sensor: Method for Establishing Correlation with Total Acid Number","volume":"86","author":"Wang","year":"2002","journal-title":"Sens. Actuators B"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1794","DOI":"10.1088\/0957-0233\/14\/10\/308","article-title":"Electrical Techniques for Monitoring the Condition of Lubrication Oil","volume":"14","author":"Turner","year":"2003","journal-title":"Meas. Sci. Technol."},{"key":"ref_24","unstructured":"Kuntner, J., Chabicovsky, R., and Jakoby, B. (2005, January 17\u201318). Oil Condition Monitoring Using a Thermal Conductivity Sensor. Proceedings of the GMe Forum, Vienna, Austria."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1502","DOI":"10.1016\/j.wear.2004.11.009","article-title":"Low-cost Condition Monitoring Sensor for Used Oil Analysis","volume":"259","author":"Raadnui","year":"2005","journal-title":"Wear"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Mobley, R.K. (2002). An Introduction to Predictive Maintenance, Butterworth-Heinemann. [2nd ed.].","DOI":"10.1016\/B978-075067531-4\/50006-3"},{"key":"ref_27","first-page":"30","article-title":"Integration and optimization of various conditions monitoring methods","volume":"10","author":"Mehdi","year":"2019","journal-title":"Int. J. Adv. Res. Eng. Technol."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Pochi, D., Fanigliulo, R., Bisaglia, C., Cutini, M., Grilli, R., Fornaciari, L., Betto, M., Pari, L., Gallucci, F., and Capuzzi, L. (2020). Test Rig and Method for Comparative Evaluation of Conventional and Bio-Based Hydraulic Fluids and Lubricants for Agricultural Transmissions. Sustainability, 12.","DOI":"10.3390\/su12208564"},{"key":"ref_29","unstructured":"American Society for Testing and Materials (2006). Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity), ASTM International. ASTM D445-06."},{"key":"ref_30","unstructured":"American Society for Testing and Materials (2016). Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 \u00b0C and 100 \u00b0C, ASTM International. ASTM D2270-10."},{"key":"ref_31","unstructured":"International Organization for Standardization (2017). Animal and Vegetable Fats and Oils\u2014Determination of Water Content\u2014Karl Fischer Method (Pyridine Free), ISO. ISO 8534:2017."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Meijer, G.C.M. (2008). Smart Sensor Systems, John Wiley & Sons.","DOI":"10.1002\/9780470866931"},{"key":"ref_33","unstructured":"(2021, October 04). Argo Hytos\u2014Operating manual: Oil Condition Sensors\u2014LubCos H2O+ II\u2014LubCos Level. Available online: https:\/\/www.argo-hytos.com\/fileadmin\/user_upload\/Manual_V2.01.16_LubCos_H2Oplus_LubCosLevel_EN.pdf."},{"key":"ref_34","unstructured":"International Electrotechnical Commission (2004). Insulating liquids\u2014Measurement of Relative Permittivity, Dielectric Dissipation Factor (tan d) and d.c. Resistivity, IEC. IEC 60247:2004."},{"key":"ref_35","unstructured":"International Organization for Standardization (2021). Hydraulic Fluid Power\u2014Fluids\u2014Method for Coding the Level of Contamination by Solid Particles, ISO. ISO 4406:2021."},{"key":"ref_36","unstructured":"National Aerospace Standard (2001). Cleanliness Requirements of Parts Used in Hydraulic Systems, Aerospace Industries of America. NAS 1638."},{"key":"ref_37","unstructured":"International Organization for Standardization (2020). Animal and Vegetable Fats and Oils\u2014Determination of Acid Value and Acidity, ISO. ISO 660:2020."},{"key":"ref_38","unstructured":"International Organization for Standardization (2015). Petroleum and Related Products\u2014Determination of the Ageing Behaviour of Inhibited oils and Fluids Using the TOST Test\u2014Part 3: Anhydrous Procedure for Synthetic Hydraulic Fluids, ISO. ISO 4263-3:2015."},{"key":"ref_39","unstructured":"International Organization for Standardization (2017). Animal and Vegetable Fats and Oils\u2014Determination of Peroxide Value\u2014Iodometric (Visual) Endpoint Determination, ISO. ISO 3960:2017."},{"key":"ref_40","unstructured":"International Organization for Standardization (2016). Animal and Vegetable Fats and Oils\u2014Determination of Trace Elements by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), ISO. ISO 21033:2016."},{"key":"ref_41","unstructured":"(2021, October 04). Parker Hannifin Corporation\u2014Online Fluid Condition Sensor (FCS) User Manual. Available online: https:\/\/ph.parker.com\/us\/en\/online-fluid-condition-sensor-fcs\/#tech-specifications."},{"key":"ref_42","unstructured":"(2021, October 04). Parker Hannifin Corporation\u2014Icount PDR User Manual. DD0000002_IPDR_EN_REV.05-2011. Available online: https:\/\/www.google.com\/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjHt5mMm7PzAhVOt6QKHUc0AqgQFnoECAIQAQ&url=https%3A%2F%2Fpdf4pro.com%2Fcdn%2Ficountpdr-parkerhfde-5b35e5.pdf&usg=AOvVaw2xxWZOb9sZ-CNtkXTs_FCK."},{"key":"ref_43","unstructured":"(2021, October 04). Argo-Hytos\u2014Operating Manual V1.07.21\u2014EN: OPCom FerroS, SPCO 500-1000. Argo-Hytos GMBH. Available online: https:\/\/www.argo-hytos.com\/fileadmin\/user_upload\/Datasheet_OPCom_FerroS_10055_EN_US.pdf."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"415","DOI":"10.4081\/jae.2013.326","article-title":"Dynamic-energetic balance of agricultural tractors: Active systems for the measurement of the power requirements in static tests and under field conditions","volume":"44","author":"Pochi","year":"2013","journal-title":"J. Agric. Eng."},{"key":"ref_45","first-page":"419","article-title":"Design and assessment of a test rig for hydrodynamic tests on hydraulic fluids","volume":"Volume 67","author":"Coppola","year":"2020","journal-title":"Innovative Biosystems Engineering for Sustainable Agriculture, Forestry and Food Production"},{"key":"ref_46","unstructured":"International Organization for Standardization (2008). Uncertainty of Measurement\u2014Part 3: Guide to the Expression of Uncertainty in Measurement, ISO. ISO\/IEC GUIDE 98-3:2008."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/24\/8201\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:43:19Z","timestamp":1760168599000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/24\/8201"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,12,8]]},"references-count":46,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2021,12]]}},"alternative-id":["s21248201"],"URL":"https:\/\/doi.org\/10.3390\/s21248201","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,12,8]]}}}