Posted on by Jón Frímann

A new geophone station added to the webicorder web page

I have added a new geophone station to the webicorder web page. The station name is Þorgrímsstaðir (Thorgrimsstadir). Tomorrow the station is going to it’s correct location. But for the next few hours I am going to run it at home for some testing and set-up proposes. At current time it does not have a GPS clock, so I won’t use the data from it until I have a GPS clock to get both location and time with atom accuracy.

This station is going to replace the Hvammstangi geophone in February 2011. But until Hvammstangi geophone goes off-line I am going to have both station online.

29 Replies to “A new geophone station added to the webicorder web page”

    2. According to http://en.vedur.is/ there are winds something like 10 m/s coming from the north in northern parts of Vatnajökull, but stations MKO and BRU seem pretty insensitive to these! So, is it really something else?

    1. The sensitivity is about the same. But there is a difference in the cable type and length. When it comes to low carrier signals likes the one from a geophone that can be a lot of difference if a cable is a 20 meter long or just less then 5 meters long.

      The difference that you are seeing is a result of that cable length difference.

      2. The signal is analogue from the geophone. The digital seismometers are way to expensive for me. I also don’t have the software for it I think.

        But for the cheaper hardware I want a Volksmeter II. It is a state of the art seismometer for the amateur earthquake monitoring.

        Too bad it costs around $2000 (about 1500€) without vat and customs here in Iceland. This is about 240.000 ISK.

        More information about Volksmeter II.

        http://www.rllinstruments.com/DS_index.htm

      3. Wonder if they knew what the name of the machine kind of sends for a signal.
        But at least I can say one thing, they didn’t put much money into the homepage 🙂
        I will see what I can do, since it is not off the shelf-technology (something we allready have) I need a board-decision to get one for you.

      5. It is not that. I am using a good shielded cat-6 net cable on the Hvammstangi station with decent connection points.

        But the maximum power from the geophone is 0.32V. That is not a lot of power and gets lost rather fast in a normal 75Ohm cable.

      6. If you had the signal in digital you could use a 50KOhm co-axial cable. Or you could use a balancing transformer and send a balanced signal like in a telephone grid for a analog signal. Much better options for long signal distances.
        The hardware for the balancing transformers wouldn’t be that steep.

      9. Oh, it doesn’t affect the frequencies. It would work as any audio amplifier you know. As long as the signal is sent in analogue form it would just be increased a bit in strength.

        What I would do is to calculate the effect loss due to cable-length and then build a really small op-amp (op-amps are the same as the small amplifier that sits right after the input connector in a stereo-amplifier and increases the voltage before the signal enters the volume control, otherwise the volume control will degrade the signal quality (like in a long cable)) that inserts the effect loss at the spot of sending. That way the signal quality is conserved a lot better than compared to increasing the gain at the point of reception.

      10. http://www.ihlutir.is
        They have a guitar pre-amplifier called Cebek PM-7 https://www.elfa.se/elfa3~se_en/elfa/init.do?item=85-866-87&toc=0

        On that one you change the op-amp into a Burr-Brown OPA-134
        https://www1.elfa.se/data1/wwwroot/assets/datasheets/eeT02029.pdf

        And then put a volume-potentiometer before the output connector. Before installing, make sure that the volume-potentiometer is put to zero. Then install and turn on, and dial it up a little bit at a time untill you have the desired gain of signal.

        Good luck!

      11. Cables make a hell of a difference when using low voltages. That is the reason after all that you always try to put maximum voltage into main feeder-trunks in electricity grids.
        Or for that matter use high square milimetre cables between the amplifier and speaker. For speakers you normally use 1mm squared for one meter length and then double for every doubling of distance.

  8. If you decide to go with the pre-amp, just make sure that you check the frequency response at the low end. (note, the op-amp is your best choice, gobs of gain and minimal cost if you build it). Though guitar and phono/mic amps are of high quality, they may have built in filtering that adversely effects the signal at the low frequencies. Sub 30hz isn’t usually where they are looking for fidelity.

    2. You are as usually fully correct. This is why I recommended switching into the Burr-Brown op-amp. My idea with the guitar pre-amp was just that it is a kit so it is easier to start building if you are not an engineer or used to DIY,

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