EARTHQUAKE VIBRATION DETECTOR AND SI VALUE-DETECTING APPARATUS

摘要

PURPOSE: To provide an SI value detector apparatus which is small, inexpensive and accurate with remarkably small noises caused by heat. CONSTITUTION: An SI value-detecting apparatus 1 is provided with an earthquake vibration detector consisting of an acceleration detection means 2 for detecting an earthquake vibration using a piezoelectric element and an amplifier means 3 for amplifying an output of the acceleration detection means 2, and an SI conversion circuit 4 for converting an output of the earthquake vibration detector to an SI value. In the apparatus 1, the amplifier means 3 has a considerably high input impedance of not lower than 2000MΩand selectively amplifies signals of a frequency band of 0.1-100Hz. The SI value detection circuit 4 selects a larger one of speed response values to two natural frequencies in a speed response spectrum obtained from the output of the acceleration sensor and multiplies the output by 1.75/2.4 thereby to obtain the SI value.