How to Use a Homemade Seismograph
MATERIALS
1 10Hz 395 Ohm Oyo-Geospace Geophone (seismic energy sensor)
1 Metal Ground Strike Plate (seismic energy source earth coupling mechanism)
1 Heavy Piece of Metal (seismic energy source)
1 Analog Voltmeter (for measuring sensed seismic signal amplitudes) 1 Amplifier DC Offset Circuit (for amplifying seismic signals sensed by geophone) -1 experimental socket board -6 volt lantern battery -47k Ohm resistor -2.2k Ohm resistor - ICL 7660 integrated circuit
- IC 741 integrated circuit -1000 Ohm Potentiometer -10 microFarad capacitor (3)
-Jumper wires (10)
-4 mueller clip leads
METHODS
The first part of this process is to obtain all electrical and electronic components for the amplifier circuit. Then obtain the geophone and analog voltmeter. Then assemble the geophone amplifier circuit and test it to ensure that it works properly. Then electrically connect the geophone to the input of the geophone amplifier circuit, and electrically connect the output of the geophone amplifier circuit to the analog voltmeter.
Then bench test the assembled system, and initially adjust the DC bias of the geophone amplifier circuit during the bench test. Confirm that the system operates properly in a bench environment. Following bench testing of the system, perform field calibration and testing of the system. Determine a good outdoor field location for the acquisition of seismic data. Plant and couple the geophone into the ground. Measure and mark a series of pre-determined distances from the geophone along the ground surface (eg, 1 ft.-51 ft. in 5 ft. increments) to define a series of energy source stations. Place the strike plate at the 1 ft. location, and energize the seismic acquisition system. Drop the piece of metal from pre-determined height (eg, 3 ft.) onto the strike plate. Visually note and record maximum voltage sensed by analog voltmeter at this energy source station. Repeat these same steps at all subsequent energy
1 10Hz 395 Ohm Oyo-Geospace Geophone (seismic energy sensor)
1 Metal Ground Strike Plate (seismic energy source earth coupling mechanism)
1 Heavy Piece of Metal (seismic energy source)
1 Analog Voltmeter (for measuring sensed seismic signal amplitudes) 1 Amplifier DC Offset Circuit (for amplifying seismic signals sensed by geophone) -1 experimental socket board -6 volt lantern battery -47k Ohm resistor -2.2k Ohm resistor - ICL 7660 integrated circuit
- IC 741 integrated circuit -1000 Ohm Potentiometer -10 microFarad capacitor (3)
-Jumper wires (10)
-4 mueller clip leads
METHODS
The first part of this process is to obtain all electrical and electronic components for the amplifier circuit. Then obtain the geophone and analog voltmeter. Then assemble the geophone amplifier circuit and test it to ensure that it works properly. Then electrically connect the geophone to the input of the geophone amplifier circuit, and electrically connect the output of the geophone amplifier circuit to the analog voltmeter.
Then bench test the assembled system, and initially adjust the DC bias of the geophone amplifier circuit during the bench test. Confirm that the system operates properly in a bench environment. Following bench testing of the system, perform field calibration and testing of the system. Determine a good outdoor field location for the acquisition of seismic data. Plant and couple the geophone into the ground. Measure and mark a series of pre-determined distances from the geophone along the ground surface (eg, 1 ft.-51 ft. in 5 ft. increments) to define a series of energy source stations. Place the strike plate at the 1 ft. location, and energize the seismic acquisition system. Drop the piece of metal from pre-determined height (eg, 3 ft.) onto the strike plate. Visually note and record maximum voltage sensed by analog voltmeter at this energy source station. Repeat these same steps at all subsequent energy