Browsing by Author "Idehen, Philip Igbenigie"

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    Design,Consruction and Testing of a low Constmulti-Channel Seimic Data Acquisation Sysytem
    (Obafemi Awolowo University, 2015) Idehen, Philip Igbenigie
    A seismic data acquisition system (SDAS) was designed and constructed using locally available electronic materials. This was with a view to developing a low cost SDAS that can be compared with the conventional imported equivalent. Three circuits were designed for the low cost SDAS. First was a +12 V DC power supply unit composed mainly of a two 12 V battery connected in parallel and bridge rectifier. Secondly, a trigger circuit was designed using a 555 timer configured in monostable mode to trigger low and high signal generated from a sledge hammer in less than 3 s time lag. This time lag would allow the milliseconds seismic wave to travel from the point of generation to the geophone. Lastly, the analog signal conditioning circuit was designed using instrumentation amplifier with high Common Mode Rejection Ratio (CMMR) for increased signal to noise ratio and amplification of the seismic signal. These circuits were soldered on a veroboard. The output of the trigger and analog signal conditioning circuit were fed into two of the analog pins of an Arduino board. The Arduino aided analog to digital conversion of the seismic signal and USB interfacing with Personal Computer (PC). The entire components were assembled in a light and portable plastic box. LabVIEW software was used to design a Graphical User Interface (GUI) to display the seismogram on PC during data acquisition and to program the Arduino to trigger the SDAS during any seismic wave generation. The expected seismic signal was displayed on the GUI during any seismic signal excitation. Field testing of the constructed low cost seismograph was carried out. A traverse length of 25 m with shot points at 5 m interval was used. At every shot point, the SDAS was able to pick and display the seismic signals. The first arrival times obtained for each shot point at 5 m, 10 m, 15 m, 20 m and 25 m interval were 49.01 ms, 42.37 ms, 37.17 ms, 40.11 ms, and 49.55 ms respectively. These results showed the inability of the offsets to vary directly with expected time of first arrival, indicating that the seismic signal timing device might not have functioned properly. The study concluded that although the SDAS identified and picked the seismic signal, the first arrival times were not accurately recorded.