Bench Test Model of the Human Skull for Testing the Variable Frequency PulsePhase-Locked Loop Instrument

摘要

The Variable Frequency Pulse Phase-Locked Loop (VFPPLL) instrument is currentlybeing used to non-invasively evaluate the human skull for increases in intracranial distances brought about by increases in intracranial pressure. It is designed to determine distance changes, in the sub-micron range, calculated from changes in frequency of an ultrasonic toneburst produced by a transducer, traversed through the skull and received back by the transducer. A bench test model of the human skull will calibrate the VFPPLL by comparing known distance changes to the VFPPLL derived distance changes, and thereby verity the accuracy of the instrument. Additionally, the bench test model will determine a broad range of operating limits on temperature, pressure and elongation over which the VFPPLL can operate accurately. Each of the three models made demonstrates a different effect on the frequency change based on the different parameters, i.e. temperature, pressure or elongation. The Open Channel Model compares closely approximated elongations with VFPPLL derived elongations, showing favorable results for calibration of the VFPPLL instrument. Specifications for creating a bench test model of the human skull for testing the VFPPLL instrument are established in this thesis.