Intelligent high pressure sensor for automotive application

Typical markets for high pressure sensors are common rail diesel, gasoline direct injection (GDI), transmission, oil pressure and brake application with their variety from medium up to high pressure ranges like 35, 70, 200, 260, 1800 up to 3000 bar. These markets require a simple, cost-efficient, reliable and robust concept. Target of the development was a pressure sensor with a minimized number of parts and the usage of state of the art processes for manufacturing. Furthermore, the advanced feature of a stainless steel membrane in harsh environment and a wide application specific flexibility in the mechanical and electrical connector design was also the objective. The pressure sensor designed by First Sensor Technology GmbH (FST) uses a special patented piezo-resistive monolithic sensor element for measuring the point stress on a steel diaphragm. The sensor works in a temperature range between -40 degrees C and 140 degrees C and has an accuracy of 1.3% depending on the temperature range. With this concept a pressure sensor with minimized outside dimensions has been developed, applicable for engine oil, diesel, transmission oil, gasoline and blend, carbon dioxide and other media in a pressure range between 35 bar and 3000 bar. The pressure sensor concept has a one part pressure connector, which is made of stainless steel and includes thread and diaphragm. Therefore, no further welding processes are needed and we also have a clear separation from pressurized media. On top of the diaphragm an ASIC including a piezo-resistive sensor element (Weathstone bridge) is soldered on a metal membrane. This ASIC includes all fail safe functionalities like an integrated sensor check of signal conditioning path and others. The sensor element has to be electrically connected by wire bonding to the PCB. The housing with integrated pins is assembled afterwards. The complete pressure sensor is calibrated in an end of line calibration. In this article the next generation of high pressure sensors for automotive and industrial applications is discussed for high volume markets. One of the most important topics is the fail safe concept and the possibilities and benefits for customers use. Furthermore, the flexibility to accomplish customer needs in combination with short development terms is also discussed. We offer to meet the customers applications like qualifying new materials, modifying outside dimensions, etc. Another topic is the robust design and a description how to withstand harsh environments. Additionally, results of the finite element analysis (FEA) are also shown.