Presented by Dr. Marek Wlodarczyk, President and CEO of Optrand, Inc. at SENSORS EXPO DETROIT, Cobo Convention Center, Detroit Michigan, October 21-23, 1997 during the Automotive Sensors: Technologies and Applications session.

Embedded Fiber-Optic Combustion-Pressure Sensors for
Advanced Electronic Engine Control

Dr. Marek T. Wlodarczyk, Tom Poorman, Liangdao Xia, Terry Coleman, Jacob Arnold


The computational capabilities of microprocessors combined with cylinder-specific ignition and fueling systems allow control of each combustion cycle for significant fuel economy improvements and reduced levels of combustion pollutants. The enabling element is a low-cost and durable in-cylinder pressure sensor. In a preferred design the sensor is embedded within such devices as spark plug/ignition coils, fuel injectors, or glow plugs. The resistance to high temperature, miniature-size, and immunity to electrical interference uniquely allow a fiber-optic combustion pressure sensor to be combined into such "smart", multifunctional devices. In a durable, robust, and low-cost design, Optrand sensor utilizes the principle of light reflection from a specially shaped metal diaphragm. Other sensor components include two optical fibers, one LED source, one photodiode detector, and a dedicated Application Specific Integrated Circuit (ASIC). A smart auto-referencing technique compensates for temperature effects on the opto-electronic components, errors due to fiber link fluctuations, and sensor drift. The opto-electronic and ASIC components, capable of withstanding 150oC temperature, are packaged inside a miniature module embedded within the package of a host device. When optimized for high linearity and minimum thermal shock, an embedded fiber optic combustion pressure sensor demonstrates total error due to non-linearity, hysteresis, and thermal shock below +/-1% of full-scale reading. With the lifetime of 500 Million pressure cycles and targeted price of less than $10, the sensor meets the performance, durability, and cost requirements for production car calibration, monitoring, and control applications.