ZERO SHIFT IN PIEZOELECTRIC ACCELEROMETERS
NAVAL RESEARCH LAB WASHINGTON DC
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Attempts to measure parameters of severe mechanical shock environments by use of piezoelectric accelerometers are often frustrated by the occurrence of zero shift. This phenomenon defeats measurements by rendering the reference line of the recorded waveform uncertain and perhaps preventing proper operation of recording circuitry as well. Possible causes include improper accelerometer application or recording techniques, as well as the design and material of accelerometer itself. In this study these possibilities have been restricted, so far as possible, to those involving the accelerometer alone, and the reactions of the zero shift phenomenon to variation of several shock parameters observed. Four accelerometers of various materials and constructions have been examined in this way. Of the two accelerometers which do not exhibit zero shift, one uses a ferroelectric ceramic element in shear mode and with light loading, and the other uses natural quartz in compression mode with moderate loading. Both of the accelerometers which do produce zero shift use ferroelectric ceramics in the compression mode with high loading. High stress on the sensing element is evidently an important factor. Further studies should attempt to explore temperature correlations as well as to separate the effects of element operating mode and stress.
- Test Facilities, Equipment and Methods