Development of the Portable Easy-Operation Long-Period Seismometer. : Part 2 : Peripheral Device.

In order to advance the stability of PELS (Portable Easy-Operation Long-Period Seismometer) in temporary or unattended operation, an application of feedback has been devised. Owing to the design, to minimize the number of electronic elements and power consumption, the circuit board can be set in the container of PELS and the power for the circuit can be provided commonly by the small DC power source prepared for the active parts of PELS. The details of the design and the effect of the device on the original frequency characteristics are discussed analytically and experimentally. By the use of PELS with this device, high magnification long-period observation can be carried out at any station without being disturbed by long-term drift due to the thermal effects or tilt effects