ERAC's first official observations by Geophones, April 2006

Chart generated by Wolfgang Arnold

Click on the chart for seeing a full view.

Geophones, where to buy

Geophones, they have 1 Hz versions as well as 4.5 Hz versions

Posting from Charles S. Osborne

The software I use for our seismometer is a program called WinSDR [ ]. Its used on the "Public Seismic Network" in California. You can see the live website output from our four geophones here at Pisgah Astronomical Research Institute [ ]. I think the software is written to only use the Webtronics ADC though. The software does get the files into a format usable by the international network of seismic stations. (We occassionally contribute files to Universities in adjacent states when asked.) And a companion program WinQuake can view and magnify earthquake event files, calculate distances to epicenter etc. may provide some other resources though I have not used this one. this one has some schematics and other useful links.

One crucial thing I learned is that a sound card usually won't work well for seismic recording because the seismic waves are below 5 Hz in frequency and most sound cards have AC coupled inputs with poor response below 10 Hz. This means you should build a very steep opamp active lowpass filter with a 5 Hz or even 1 Hz corner frequency. That gets rid of AC hum and VLF and above RF pickup while helping focus on the signal of interest. For our geophones an opamp gain of x600 ~ x1000 built into the filtering was optimum. Then a standard ADC can be used to capture the seismic signal.

SkyPipe using its MAXIM MAX186 / MAX187 ADC optional input type circuit might work well for the graphing and data sharing.

Charles S. Osborne
Technical Director

Pisgah Astronomical Research Institute
1 PARI Drive, HC 73, Box 638
Rosman, NC 28772-9614
828-862-5813 direct
828-862-5554 main
828-862-5877 FAX

From Peter Wright

You can mount the geophon with a spike driven into the ground. That is light in weight. This way you can use easy a geophone to listen to the earths digestion noises. Do not even think of mounting a Geophone on a heavy weight. This damps the effectivness of the geophone because the sponge earth around the weight acts as a shock obsorber and the weight sinks into it if the earth quakes. I have driven a 1.5 meter water pipe into the ground vertically and my Geophone is mounted to it with 2 componant glue "Araldite". This ensures that when the earth moves in Z direction that the geophone follows.

You need a 2 core shielded cable to go to the Op amp driver and then a sound card I am still looking for seismographic software in the internet has anyone found anything yet ?

Regards Peter

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