An acoustic automotive engine oil quality sensor

A prototype model of an Acoustic Engine Oil Quality (AEOQ) sensor is presented. The AEOQ sensor utilizes changes in oil viscosity as an indicator of the oil quality. The viscosity is measured using a shear mode piezoelectric sensing probe. The supporting electronic circuitry employs a novel Voltage Control Oscillator (VCO) based set-up which allows for remote excitation of the piezoelectric sensing element. This feature is important because it permits the electronic circuitry to be several feet away from the harsh environment of automotive engines. Additionally, the output signal from the VCO set-up is a DC voltage, which simplifies the accompanying circuitry, and is compatible with existing automotive electronics. These features make the VCO configuration the setup of choice over previous methods based on oscillator type detection circuitry. The AEOQ sensor is capable of differentiating between engine oils of different grades and monitoring the degradation processes of oils due to their use in automotive engines and due to artificial contamination by dilution with water, ethylene glycol, and gasoline.