Technical Paper
Methods of Processing Cylinder-Pressure Transducer Signals to Maximize Data Accuracy
1990-02-01
900170
Two disadvantages of using piezoelectic pressure transducers to measure cylinder pressure are the sensitivity of the transducer to temperature and the necessity to reference the output to absolute pressure (pegging). Transducer drift driven by the combustion event, often referred to as thermal shock, enhances measured cyclic variability by exaggerating the effects of actual cyclic variations in combustion temperature. Any artificial variability that persists until the portion of the cycle used for pegging offsets all of the referenced measurements of that cycle by the magnitude of the variability. This study reviews several methods of pegging, and examines the extent to which the four most viable methods propagate thermally-induced intracycle and intercycle measurement variability. It is preferable to peg when artificial variability is minimized, which occurs when the transducer output is least affected by the thermally transient nature of the engine cycle.