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GeoPhone reading notes

(1) Project 6 years old
(2) 16 bit ADC with AGC not longer expensive
(3) 100Hz OK, even 0.001 Hz
(4) FGS (Fellow of GeolSoc)
(5) Gert Board
(6) Sample rate order of 4ms
(7) real bed rock, lots of urban noise and under the flight path for a major international airport.
(8) Low pass filters will help remove a lot of the noise
(9) three-component seismometer. However, a single vertical component (as you’re describing) would probably be ideal for a school project. Keep it simple,etc.
(10) horizontal one
(11) I’m currently building the unit from some wood scraps i had lying around, an aluminum rod and a concrete weight i made a few years back when i was experimenting with concrete. i’m planning to have a period of 8 seconds or less, and will (as of now) record the data on a spool of paper rotated with an outlet timer. The timer originally ran at 50Hz but we get 60Hz here so it should run a bit faster.
(12) Sample speeds: Yes passive seismometers typically have resonant frequencies measured in seconds (ranging from tenths up to perhaps a minute
or two – but even longer periods are now available).
(13) ll try with a filter of .3Hz
(14) calibration issues i’ll wait until an earthquake rolls by
(15) small three axis accelerometers that can connect using the I2C bus that’s available on the GPIO port. There will be a library to communicate with it because this will be a popular way to connect sensors.
But will the sensitivity of a small accelerometer be good enough? It will obviously detect major earthquakes but smaller ones?
(16) Just put it on a jiggle table thingy. We have one here for testing cameras, can run from 0.1Hz to 10Hz I think at variable amplitude, in two axis (pitch and yaw). Mind you, it did cost 20kEuro. Bit of a rip off I reckon.
(17) know it isnt very DIY buy you might want to take a look at the quake catcher network at stanford http://qcn.stanford.edu/
(18) A while ago, for fun I made a horizontal seismograph (swinging-door type) out of wood, a copper coil, and magnets from a hard drive. The period was a few seconds. Problem is I live in an urban area and almost all the signal was from traffic outside, A/C in the building, etc.

On the subject of A/D converters, you can get 18 bit A/D converters fairly cheaply, for example the MAX11209 is about $6. Main problem for a hobbyist is it comes in a tiny QSOP package; hard to hand solder (although I did it!- using a QSOP-DIP adaptor). It has configurable gain, and can do 120 samples per second (actually up to 480 sps, but in that mode each sample is not truly independent). I put some test data from that ADC here: http://dangerousprototypes.com…..038;t=3818

There are cheap high-resolution audio A/D devices, but few or none of those have DC response, which you probably want. Unless you are getting fancy and modulating your signal, and then using a lock-in detector approach. That’s feasible, but complicated.

(19) Hi, I don’t know what do you expect from your “home made” seismometer, but I work in a Seismological Research Center (I work on maintenance).

(20) ADC starting from 20 bits ap to 24 bits.
(21) Then, you also need a software to “detect” seismic wave from “others” waves.
(22) Keep in mind, if you’ll build a “serious” seismometer, it will be very sensible to external “noises”, like steps, cars, and so on.
(23) MCP3423 which has 1
(24) The general consensus seems to indicate that we are only interested in frequencies below 10Hz; in fact my design has a 6 pole filter with a 10Hz cut-off. A popular electronic design by Infiltec for Lehman seismometers uses sampling at 34 SPS with 16 bit resolution; I’m using that as my initial baseline requirement.
(25) Why don’t you let Google be your friend!

1. http://www.circuitlake.com/long-period-seismometer.html

more details at

2. http://www.infiltec.com/seismo/inf-qm10.htm

Although this gentleman sells modules and kits, he does also publish the circuit schematics for his design, they are on the site but a bit hard to find.

This is for a PIC controller, but I am sure you can use your pi instead, if you really need to!
(26) Shackleford-Gunderson Seismometer.
(27) The main reason for not considering the Infiltec unit is my seismometer uses a capacitive detector which is not compatible with the Infiltec coil/magnet design.

(28) Public Seismic Network site, http://psn.quake.net/ which is dedicated to home brew seismometers. It’s been going for decades and even has Dr Lehman posting from time to time. There’s a wealth of information there on all aspects.

(29)
For local quakes you need to capture signals up to 10 Hz.
For tidal effects (microseisms), they are usually around 0.17 Hz
For international quakes (teleseismic), they’re between 1 to 0.01 Hz, generally, for us amateurs.

For plotting, have a look at PGPLOT, though there may be something easier these days.

(30)
I post the results to http://www.iasmith.com/ Currently the sensor driving the lower graph is broken (a 4 Hz geophone) and I think a spider has gotten into my Lehman enclosure (top graph).

(31) its great to see people interested in homebuilt seismometers. You might like to check out some of the resources that we have made available at http://www.bgs.ac.uk/ssp this is an education outreach project aimed at helping schools set up their own seismic monitoring station (although there are a few amateur enthusiasts involved as well). On the website you can also exchange data that you have recorded with other users in the UK/Ireland/USA and europe Most schools have been using the SEP seismomeetr system http://www.mindsetsonline.co.uk/product … ts_id=9047 although we are trying to encourage schools to make their own. You can also by the SEP digitser box on its own (x100-x500 gain 16bitADC 20sps rs232 output £109 ) which would interface well with your homemade seismometer. we use the free amaseis software for data logging (windows only) although apltaform independent java replacement for this is due for Beta release this summer.

(32) Re: Raspi-powered seismometer/seismograph
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2012-Jul-09 Mon 8:25 pm

The python based scripts (called miniseis)were written by Jon Gilbert last year as part of his coursework at Edinburgh University. They take data from an SEP digitiser (which just produces a stream of 16 bit numbers 20 times per second onto a serial port). The code was originally written to work with the SHEEVA plug computer (an embedded linux system). The serial data comes into the SHEEVA through a USB-serial convertor. I see no reason why this should not port easily to the RasPi ( do not know whether we would need to use a USB-serial convertor or if the RAspi could read serial data directly on GPIO pins.)

The raw data is stored locally in both raw binary format (as read by Amaseis software) and also as a compressed format called miniseed (as used by seismologists all over the world). The code also broadcasts data live over a TCP connection using the same server-client protocols that AMaseis uses. It can also send data in packets to a remote web server using HTTP push. The software makes use of the Obspy python package for writing miniseed and some other functions

http://www.mutzi.co.uk/docs.tar
http://www.mutzi.co.uk/miniseis.tar
http://obspy.org

also see http://alomax.free.fr/seisgram/SeisGram2K.html for platform independant (java) seismic analysis code which reads seismic data in miniseed format
http://www.mutzi.co.uk/docs.tar
http://www.mutzi.co.uk/miniseis.tar
http://obspy.org

also see http://alomax.free.fr/seisgram/SeisGram2K.html for platform independant (java) seismic analysis code which reads seismic data in miniseed format

All code is open source

please feel free to email me directly if you have any queries or just to let me know how you are getting on (pdenton@bgs.ac.uk)

you might also be interested in Graeme Keon’s work on using soundcards to record seismic signals
http://motivationtolearn.org/wordpress/ … #more-1100. He uses a uses a 555 chip to modulate an audio frequency carrier with low frequency seismic signals and then record them on a cheap soundcard.
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https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=3731&start=25#p235602

Re: Raspi-powered seismometer/seismograph
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2012-Dec-17 Mon 9:43 am

It’s a version of a fairly standard design called a Shackleford-Gundersen Seismometer. This is a 1975 design but I have updated the electronics and done all of the later improvements. A lot of folks build what is called a “swinging gate” design attributed to Lehman and it works well too but the SG unit has a smaller footprint and I just like the design better.
Once things are starting to “join up” convincingly I will post more along with some photos and, of course, the source code.

David

“swinging gate”

Re: Raspi-powered seismometer/seismograph
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2013-May-03 Fri 7:44 am

Hi Folks:
I hope you have a good experience putting together an earthquake seismometer.
This link,
http://www.jsasoc.com/diamagnetic_suspe … smomet.htm
describes a VERY SIMPLE novel seismometer, using a pure graphite rod suspended
in a strong magnetic field. It responds to displacement, not velocity.
There are several design issues that need to be solved to make this work properly.
I tinkered with this but lost interest. I hope someone else takes up the project.

BTW I don’t think you need lots of dynamic range in your ADC. Just look at (analog) earthquake records from years ago. They managed just fine with line widths of about 1 mm and chart widths of
about 300 mm, which is equivalent to about 8 bit resolution.
In modern times there are lots of interesting cheap ways to do the ADC.

The schools seismograph project at http://www.bgs.ac.uk/ssp looks really promising.
CHILE 8.3 Earth Quate
https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=3731&start=25#p817269

HX711

Re: Raspi-powered seismometer/seismograph
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2017-Feb-13 Mon 1:44 am

Now that my seismometer is essentially finished and working flawlessly in a corner of the garage, I have begun another seismometer project with a friend who has been working on a Lehman seismometer since the early 1980’s. It’s still not quite working yet, so I’ve been pushing him to finish it. Initially he was going to just print the output of his 1980 electronics (which has not proceeded past the paper design point) to a drum plot (a real one that uses paper…OMG!) but I believe that he is now tending toward a more software driven approach to recording the data. Computers are not his thang.

It was ChucktheTinkerer’s post about the HX711 that got me started thinking about a very cheap 24-bit ADC interface for an amateur seismometer with velocity sensor. The HX711 has all of the necessary components to process the output of a velocity sensor: 24-bit resolution with sample rates of either 80Hz or 10Hz, a programmable gain pre-amplifier with gain values of 32, 64 and 128, and a fully differential bridge-type interface. I ordered a pre-built module from eBay for about $1. After a few hours of “tinkering” with it I realized it’s potential as a seismometer interface, but I had to toss out the eBay module to unleash it.

The HX711 datasheet shows an application using its internal/external regulator to provide a quiet analog supply for the ADC. They also say that if the on-chip regulator option is not used, the two supply pins can be connected to a separate regulated supply. This is a better option for use with the Pi because the Pi GPIO interfaces operate at 3.3V and the HX711 supply range is specified over 2.6V – 5.5V.

I also found that the HX711 internal clock generator was more than 20% low on the eBay board. This may be why it only costs a buck. This is not really acceptable for a seismometer — the seedlink server software is a bit sensitive to variable sampling rates. But the HX711 provides for a crystal controlled clock (not an option on the eBay board, which is hard-wired at the slow sample rate.)

The HX711 ADC requires its inputs to both be within a certain common mode range but the eBay board did not provide any circuitry to accomplish that.

The one-shot is the most expensive component. I used the very cute LTC6993-1, which only needs a single resistor to program a 1us pulse. Its outrageously priced at $3.35 at Digikey, but LTC sent 2 samples to me gratis. (I guess it pays to be an alumni — full disclosure.)

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It is a velocity sensor and I think several orders of magnitude more sensitive to a given local or distant quake than the accelerometer in a smartphone. My copy of the R-Shake showed a clear signal way above background on a M7.8 quake over 4000 km away (Solomon Islands -> CA) and other people with the same unit saw it from 10000 km. I’d be amazed if a cellphone sensor would have detected that signal above noise level. If you like numbers, have a look at the modeled noise performance: http://bnordgren.org/seismo/RSS_Spice_Results.pdf

Using a so-called “hyperdamped” electronic sensing circuit, they have demonstrated it actually does show some response with very strong quakes down to 0.06 Hz although that is clearly way down in the sensitivity curve.

Re: Raspi-powered seismometer/seismograph
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2018-Apr-18 Wed 6:37 am

I don’t personally know of such software, but most of the quakes I’ve seen have a characteristic spectrogram profile that is unlike most ambient noise from traffic, etc. There is a sudden start followed by an exponential decay over 10s of seconds or more, and at any moment in time the larger signal amplitudes are in the lower frequencies eg. below 2 Hz unless the quake is very close by. A typical truck driving by on the street has a symmetric rise and fall, and usually peak energy is higher in frequency (eg. 5 Hz) and very little energy below 2 Hz. Signals from very distant quakes are almost all below 2 Hz in frequency, as the higher frequencies are more quickly attenuated in the ground.

To really tell if a signal is a quake you need to compare many stations in a network, then you can clearly tell what is very localized noise, and what signals have been received by many stations in different locations and all with a travel-time delay consistent with a common source point. You can also calculate depth, and that separates earthquakes (some km deep usually) and man-made events like quarry blasts (at the surface).

software for seismic monitoring and analysis
Report this postQuote
2018-Apr-20 Fri 5:23 am

There is some software for this available called “ObsPy” for Seismic Observatory in Python: https://docs.obspy.org/tutorial/index.html and it has many different functions and capabilities.

Here is a page describing various “triggers” available to detect quakes in the presence of noise, both from features in a single channel, and also from coincident detections within some time range, from a sensor network: https://docs.obspy.org/tutorial/code_sn … orial.html

Here is an example for calculating the apparent direction to an event, based on relative timing of signals from five stations at known locations:
https://docs.obspy.org/tutorial/code_sn … lysis.html
Re: Raspi-powered seismometer/seismograph
Report this postQuote
2018-Jul-07 Sat 1:10 pm
https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=3731&start=50#p1337900

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