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Title
Vorrichtung und Verfahren zum Bestimmen des Alterungszustands fluessiger Medien
Date Issued
1998
Author(s)
Leidl, A.
Patent No
1997-19706486
Abstract
This new equipment determines ageing of a fluid, especially (engine) oil. Physical properties of the fluid are measured initially and subsequently. A comparator determines the state of the fluid from these results. Also claimed are the corresponding procedure and sensor unit. Preferably the instrument measures viscosity, viscoelasticity, density, dielectric constant and/or the fluid conductivity. To measure viscosity, viscoelasticity and/or density, a surface wave sensor (SAW device) is used. This has interdigital transducers (12, 14). Dielectric constant and/or conductivity are measured from the complex impedance exhibited by one of the transducers (12). This transducer is connected to a first oscillator, allowing the resonant frequency and/or damping of the electroacoustic waves produced, to be determined. This yields values for viscoelasticity and/or damping. USE - To determine the state of ageing in a fluid, especially engine oil, enabling a rational replacement decision. ADVANTAGE - A comparatively simple interdigital sensor unit, a piezoelectric surface acoustic wave device (SAW), with appropriate instrumentation, takes a surprising wide range of physical measurements as described. This allows good oil to be retained, rather than replacing it unconditionally on only loosely relevant measurements of engine operating time or distance interval. It overcomes any possible tendency of engine manufacturers, in consultation with oil suppliers, to over-specify oil change frequency, ostensibly in the interests of reliability.
Language
de
Patenprio
DE 1997-19706486 A: 19970219