Low-cost microcomputer-based instrument for detecting seismic activity using a magnetic vibration sensor

Date

6-2002

Degree

Bachelor of Science in Applied Physics

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nelio C. Altoveros

Abstract

A low-cost microcomputer-based instrument for detecting seismic activity using a moving magnet phonograph cartridge needle was designed to approximate the efficiency of standard but expensive seismic instruments. A spring mass system using elastic tape measure as leaf spring was developed based on the design of modern seismometers to detect vertical vibration. The vibration sensor used was a SHURE N-44-7 phonograph stylus replacement needle. The signal was conditioned by a voltage follower circuit before converted to digital via a data acquisition system. A device controlling program was developed to facilitate the conversion, storage and processing of the data. This instrument was tested and evaluated at the Philippine Institute of Volcanology and Seismology, Diliman, Quezon City. The data generated by the instrument was compared to that of a standard seismometer. The data was processed and analyzed using correlation and waveform analysis. Results revealed that the instrument designed was successful in detecting seismic activity. The vertical displacement of the sensor was highly correlated with the voltage generated by the system with a correlation coefficient of 0.99. As can be observed in the plot of the raw data and the Fast Fourier Transforms of the data, the behavior of the data generated from the spring mass system approximated the pattern exhibited by the standard seismometer. However. the voltage output of the instrument was small compared to the voltage output of the standard seismometer. which resulted to the clipping of the magnitudes of the peak voltage readings. The precision of the instrument was limited to only up to 10-3 voltage readings. Moreover, the instrument was not able to register minute incremental movements. The phonograph stylus shows considerable potential in detecting ground movement generated by people, vehicles and even massive movements of the ground. However, the instrument requires refinement as to its sensitivity in monitoring and simulating the very minute ground movement.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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