In this paper, a capacitive sensor based on printed circuit board was designed and fabricated to detect air bubbles that appear in the engine lubricating oil. A three-electrode capacitive sensor structure is designed and simulated for monitoring and estimating amount and size of air bubbles in oil. | VNU Journal of Science: Natural Sciences and Technology, Vol. 31, No. 1 (2015) 8-16 Fluidic Capacitive Sensor for Detection of Air Bubble Inside Engine Lubricating Oil Nguyễn Đắc Hải1, Vũ Quốc Tuấn2, Trần Thị Thúy Hà1, Nguyễn Ngọc Minh1, Chử Đức Trình3 1 2 Posts and Telecommunications Institute of Technology, Hanoi, Vietnam Institute of Applied Physics and Scientific Instrument, Vietnam Academy of Science and Technology, 18 Hoàng Quốc Việt, Hanoi, Vietnam 3 VNU University of Engineering and Technology, 144 Xuân Thủy, Hanoi, Vietnam Received 10 October 2014 Revised 20 October 2014; Accepted 18 March 2015 Abstract: In this paper, a capacitive sensor based on printed circuit board was designed and fabricated to detect air bubbles that appear in the engine lubricating oil. A three-electrode capacitive sensor structure is designed and simulated for monitoring and estimating amount and size of air bubbles in oil. The capacitive sensor consists of three electrodes that are structured by the PCB, copper sheets and vias. The oil pipe as a fluidic channel is threaded through the hole of capacitive sensor. By using that structure, air bubble inside fluidic channel can be detected in realtime monitoring. Simulations showing the change of signal in correspondence to the volume of air bubble inside oil channels are compared to the measurement to give a good idea of fabrication structure. In this measurement, this capacitive sensor can monitor an air bubble with a small size of mm3 to mm3. The occurring of multi air bubbles is also monitored by this capacitive sensor for distinguishing each bubble when the bubbles have a small distance among them. Keywords: Capacitive sensor, Fluidic sensor, Air bubble detection. 1. Introduction∗ This problem is exacerbated when the air bubbles move into the high-pressure environment where changes in volume caused a drastic increase in temperature. In machine environments where dramatic pressure changes occur, such as a hydraulic .
