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A study on the etching characteristics of magnetic tunneling junction materials using DC pulse-biased inductively coupled plasmas

We designed and fabricated the engine oil monitoring sensor to measure engine oil deterioration through increased vehicle mileage. Since the condition of the engine oil can be affected by the state of the vehicle and its operating conditions, it should be directly measured and determined in every vehicle. The fabricated sensor has an aluminum parallel capacitor structure that measures capacitance related with the dielectric constant, which is one of the indices of oil deterioration. The size of the capacitor is small enough that it could be easily adapted on the oil level gauge without introducing any change in the design. The fabricated device is installed in the diesel engine to measure the change in capacitance accurately as the vehicle moved from 0 km (new engine oil state) to 11,364 km. The results showed the maximum value at around 5,000 km, and the values plateaued as mileage increased, corresponding with the measurement result of the TAN (Total Acid Number). Based on the results, the condition of the oil must be monitored regularly though oil change is recommended once the vehicle has traveled the distance of around 10,000 km.

A capacitor-type engine oil sensor is designed and fabricated to measure the property of the diesel engine oil depending on the vehicle mileage. This sensor has flat structure with the interdigitated (IDT) electrodes for the smooth oil flow and is constructed using printed circuit board (PCB) for the fabrication convenience. For the increased capacitance, the smaller spacing between the electrodes is preferred and determined with 0.5 mm based on the fabrication limit. The device is applied to actual trucks with diesel engine. From the experiment, the capacitance of vehicle A is initially constant and then increased upto approximately 6,000 km. And then, the output is dramatically decreased, which indicates that the engine oil has been degraded and should be replaced. The interval at which the reduction in capacitance occurs varies depending on each vehicle, which means the exchange interval of engine oil is different from each other. The degree of deterioration of the oil is also measured with the viscosity tests and total acid number (TAN) tests, and the results are compatible with the measurement of capacitance. From these results, it has been confirmed that the fabricated IDT capacitor sensor can measure the engine oil conditions depending on the mileage.