High-Accuracy Low-Cost Cylinder Pressure Sensor for Advanced Engine Controls

A high-accuracy and low-cost cylinder pressure sensor reported in this paper compensates for all major temperature errors encountered in internal combustion engines. The auto-referencing technique maintains sensor calibration compensating for temperature effects on the sensor signal conditioner over the range of -40 to +135°C. In an inexpensive design sensor head materials and dimensions are optimized to compensate for the mid-term thermal errors associated with engine load changes over a temperature range of -40 and 300°C, resulting in the thermal coefficient of sensitivity as low as 0.005%/°C. A miniature, specially shaped diaphragm results in less than 0.5% error associated with rapidly changing combustion gas temperatures. Under non-combustion conditions the sensor offers +/-0.25 - 0.5% accuracy while under combustion conditions the accuracy is typically in the 1- 2% range.