Ground couplings and measurement frequency ranges of vibration transducers

Vibration transducers do not faithfully follow the ground motion at high frequencies, since a resonant system is formed by the weight of the vibration transducer and the contact compliance of a placing point. Particularly, the contact resonances cause errors in measurement and place restrictions on the measurement frequency range. The characteristics of the effect of ground coupling depend on the type and condition of the ground surface and the method of planting the transducer. This paper examines the characteristics of the frequency response of the vibration transducer placed on the ground and provides the optimum relationships between the base area and the weight of the transducer for decreasing the effect of ground coupling under all conditions. The relationships are represented in the figures for the user’s convenience. When the vibration transducers designed to satisfy the relationship proposed here are employed for the measurement of the ground vibration, it is shown that the errors in measurement caused by the ground coupling decrease considerably. As compared with the old vibration transducers the measurement frequency ranges are markedly spread out.