Vibrations, sensor interfaces/surfaces

Orientation of Sensors. Tissue-, interface-, and structure-mounted sensors may be aligned as closely as possible with the axes of a biodynamic coordinate system (see, for example, Fig. 10.2), even though these may have inaccessible origins that are anatomical sites within the body. In practice, sensors are commonly oriented to record the component accelerations defined by the basicentric coordinate systems shown in Fig. 10.2 (ISO 2631-1, 1997 ISO 5349-1,2001), which have origins at the interface between the body and the vibrating surface. The location of accelerometers to record the handle vibration of specific power tools is described in an international standard (ISO 5349-2, 2001). 

This works on the principle that any change in the environment concentration is reflected as a change in mass of the sensing interface which is then measured as a variation in vibration frequency. Sensors working by this principle are alternately termed surface acoustic wave (SAW) resonators. ... 

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