Adaptation of pendulous seismometer S-5-S for measurement of rotation component of seismic vibrations

Jaromír Knejzlík, Zdenìk Kaláb, Zdenìk Rambouský

Modification of seismometer S-5-S for measurement of rotation component of seismic vibrations is described. Mechanical system of S-5-S consists of sensing and dumping electrodynamical transducers mounted on unsymmetric two-arm pendulum which is suspended by two cross flat spring hangings. Pendulum is balanced by spring. Described modification of S-5-S consists of removing of the spring and balancing of pendulum by supplementation of additional mass on the damping arm. Additional strain-gauge sensor of rotation displacement is installed on flat springs hanging. Main dynamic parameters of resulting rotation sensor, e.g. natural period and damping of sensor, are controlled by feedback signals of rotation displacement and rotation velocity that are conducted to the damping transducer. Sensor enables measurement of movement around vertical or horizontal axes. Output signal can be proportional to the rotation displacement or rotation velocity.