A horizontal vibration detector using a leaf spring pendulum and magnetic levitation of a permanent magnet

点击翻译按钮获取中文摘要

levitation for a pendulum weight. The levitation employs permanent magnets magnetized by N, S strip, alternatively. This pendulum has been built and evaluated by experiments. The results of the experiments are as follows. 1. The prototype of the pendulum achieved a natural period more than 11 s. 2. The natural period of the prototype was changed with a magnetic spring. These values of the period were consistent with theoretical calculations. 3. The prototype with a feedback control circuit, a feedback control coil and a capacitance displacement sensor worked as a servo-type seismometer. 4. The observations using the magnetic levitation seismometer have been carried out and showed capacity to measure microseisms.In addition to the above mentioned results, fabrication method for the control circuit was improved to achieve further low noise. The control circuit employs Strip Line technology that a microwave circuit usually uses. The Strip Line can improve isolation between devices on the circuit board. The structure of a DC 10 V power supply for the control circuit was also modified for obtaining long term voltage stability and low noise. This feature of the modification is using a battery connected between DC regulators. One regulator of them is to convert from AC 100V to DC 13 V. After this circuit, there is the battery. The DC 10 V regulator is connected to the battery. This power supply showed the noise level above 1Hz is about -140 dBV and the long-term voltage stability is order of 10^<-6>.