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New electronic tongue as oil tester
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Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung E.V.
: 13 May, 2003 (New Product) |
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In the early days of mass motoring, in the 1950s, a car became due for inspection and oil change roughly every 3,000 kilometers. Since then, improvements to car engines and oils have lengthened this interval to around 30,000 kilometers, and it is likely to increase still further: to three times that figure, in the years to come. |
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Nevertheless, the decision on when to change the oil in an engine or hydraulic system is usually based on the manufacturer's recommendations, rather than a rational analysis of the individual case. Only operators of large plant, such as ships' engines or hydraulic cranes, can afford to determine the 'actual age' of the oil by sending a sample to a laboratory for chemical analysis. This could soon change, once a new sensor is ready for series production. It is being developed by the Fraunhofer Institute for Physical Measurement Techniques IPM, in a joint project with the industrial research association FVV (the german Forschungsvereinigung Verbrennungskraftmaschinen).
Some hurdles still need to be overcome before the 'electronic tongue' is capable of reliable continuous operation, as project manager Martin Jägle explains: 'In particular, the corrosion, silting and glazing of the surface of the sensor is posing some problems. But we are testing a computational method of counteracting the associated signal modifications.' The sensor consists of a number of electrodes placed at differing distances from one another on a surface smaller than the size of a fingernail. If the surface becomes evenly soiled or worn, there is a sharp drop in the level of all measured signals. This difference can be used to determine the contact resistance between electrode and oil, which can then be eliminated by calculation.
Another important variable is the total base number, or TBN. Sulfur and nitrogen compounds in the exhaust gases cause the acidity of the motor oil to rise gradually. The acids may corrode metal parts of the engine. To avoid this, oil manufacturers use alkaline additives in their products which neutralize the acids. Consequently, the decline in the value of TBN is a significant indicator of oil quality. In order to obtain a reliable signal, the sensor also measures the water content and temperature of the oil. The electronic tongue is currently being tested for use in car engines. But before it can be mass-produced as a standard component, a low-cost manufacturing process needs to be developed in which the sensor is applied as a thin film onto a ceramic substrate of aluminium oxide. |
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