Long-life fibre-optic pressure sensors for control and monitoring of combustion engines

In a robust, durable, and low-cost design Optrand pressure sensors utilise the principle of light intensity changes, transmitted by two optical fibres, upon reflection from a specially shaped metal diaphram deflecting under the effect of pressure. The non-contact detection principle combined with the diaphragm design optimised for infinite fatigue life translates into a sensor with extraordinary lifetime. The sensor's miniature signal opto-electronic conditioner is embedded inside a miniature "smart" electrical connector. Due to its small size and EMI resistance the sensor can be integrated into multi-functional pressure sensing fuel injectors, spark plugs, or glow plugs. Over the period of three years the sensor has been used in gasoline, diesel, and natural gas engines. In the longest application to date, Optrand combustion pressure sensors have demonstrated over 20000 hours or 1 billion pressure-cycle service lifetime in large-bore stationary gas engines of pipeline compressor stations. In fuel injection applications the sensor offers typical +/-0.5% accuracy while combustion pressure sensor accuracy is typically in the 1-2% range.