ABSTRACT
In December 1975, the Biomedical Electronics Resource at Case Western Reserve organized its first workshop on indwelling and implantable pressure transducers. A new principle for pressure sensing has emerged which is the time delay of surface acoustic waves on crystalline material. The oscillating frequency will vary if the material is bent under pressure or stress. The design process has begun on an integrated circuit capacitive pressure transducer where one of the on-chip capacitances will be changing with external pressure, another will be for reference, and MOS circuits will be used to excite the impedance bridge circuit and to process the output signal. For the intracranial pressure monitoring of head trauma or hydrocephalus, intracranial fluid pressure readings may be desired over a period greater than a few days. There are several other methods for designing surface acoustic wave pressure transducers, including phase measurement of delayed waves and the use of an acoustic cavity.
