Popular Marine Engine Manufacturer uses MTI Capacitive Sensors to Precisely Measure Engine Oil Film Thickness - MTI Instruments - #1

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MTI Instruments, Inc. 325 Washington Avenue Extension Albany, NY 12205 PH: +1-518-218-2550 OR USA TOLL FREE: 1-800-342-2203 FX: +1-518-218-2506 sales@mtiinstruments.com www.mtiinstruments.com APPLICATION NOTE Popular Marine Engine Manufacturer uses MTI Capacitive Sensors to Precisely Measure Engine Oil Film Thickness Introduction Marine engine manufacturers are faced with the constant and diffi cult challenge of designing and building engines to operate under the most severe environments, engines that must be long lasting, extremely reliable and perform fl awlessly even under less than ideal operating conditions. Unlike an automobile engine, marine engines are constantly under strain, even when cruising at low speeds. Harsh exposure to the elements such as salt spray, heat and cold, as well as constantly changing loads and operating conditions contribute to the problem. The Problem MTI was challenged by a top marine engine manufacturer to design a non-contact sensor to measure the microscopic oil fi lm layer between the engine cylinder wall and the piston ring. Oil fi lm thickness is an important parameter in engine development, and directly relates to oil consumption and engine life as well as effi cient engine performance and emissions reduction. Engine testing is typically performed at high RPM’s with piston linear speeds approaching 500 inches/second. A measuring system with high frequency response and small sensor size was required to keep engine machining to a minimum, and not change the engine operating characteristics along with the ability to obtain dynamic measurement data as the piston ring passes the sensor face. The Solution MTI engineers arrived at a unique miniature sensor design with a diameter of 5.5-mm, measurement range of 50 microns, resolution better than 0.25 um and a response time of 20 kHz. The sensor was threaded to offer ease of mounting into the cylinder bore and precisely machined to allow the sensor face to be fl ush or slightly recessed into the cylinder bore. Accumeasure™ capacitive sensors measure the minute capacitance change due to the oil thickness variation and convert this change into a thickness measurement. The sensor offered a rectangular 0.12-mm x 1.25- mm sensing area and the resulting footprint was designed to be considerably smaller than the piston ring width to allow it to measure only the piston ring oil fi lm thickness. High temperature epoxy and materials were used in the probe fabrication to enable it to operate at temperatures as high as 285 C (545 F) and to withstand high pressure. MTII appnote: oilfi lm.pdf - Page 1 of 2