Uncategorized

geophone notes

Asked 
Viewed 7 times
1

I’m a seismic geophysicist and would like to attach a geophone – which is basically a transducer – to any type of RP. The types and costs of geophones are both variable and extensive (in some cases). The main idea to note is this: a geophone (or array of geophones, perhaps) usually records ground displacement in 1-, 2-, or 3-D and sends the signal off as either an analogue or digital output. I want to record that signal in real-time via a RP and (eventually) develop a pipeline to send that data to a cloud database.

How might I do this?

 New contributor
  • 1
    Hi @Nathan Benton, Welcome and nice to meet you. Your question is interesting. So I wikied to know more: Geophone Construction – Wikipedia (1) Geophones have historically been passive analog devices and typically comprise a spring-mounted wire coil moving within the field of a case-mounted permanent magnet to generate an electrical signal. (2) Recent designs have been based on microelectromechanical systems (MEMS) technology which generates an electrical response to ground motion through an active feedback circuit to maintain the position of a small piece of silicon. / to continue, … – tlfong01 1 hour ago   
  • (3) The response of a coil/magnet geophone is proportional to ground velocity, while MEMS devices usually respond proportional to acceleration. MEMS have a much higher noise level (50 dB velocity higher) than geophones and can only be used in strong motion or active seismic applications. / to continue, … – tlfong01 1 hour ago   
  • I am not too sure if what the wikipedia says is correct and update: MEMS has a higher noise level (50 dB velocity higher). I think we can google “geophone” “MEMS” to get some updated info. I read that there are many methods to filter the noise, say using digital filtering and other methods of DSP (Digital Signal Processing). I read wiki’s sections on construction and frequency and have the feeling that they were a bit out of date, and perhaps not compiled by digital signal processing experts. So there is hope that traditional “three spring coil” system is not that superior than MEMS. .. – tlfong01 1 hour ago   
  • A couple of weeks ago I read in this forum about vibration detection sensors which I remember is also using ” coil springs” which I think can be very accurate (because IT advances too fast that the domain experts expect. / to continue, … – tlfong01 59 mins ago   
  • You might read my question to this question on 801 vibration sensor. I happen to have a couple of such sensors in hand. There are cheap, but as other MEMS sensors using in smart phones, because of huge mass production, become very powerful. An example is the NASA space quality of miniature camera, using ZEISS lens. Other examples include very high quality audio micro phone, with professional noise filtering (OK not very loud, but very HiFI) raspberrypi.stackexchange.com/questions/104752/…. – tlfong01 50 mins ago   
  • In short, I think MEMS and smart phone technology, together with real time cloud big data base data and AI neural network non algorithmic pattern recognition should replace mechanic spring coil stuff. I do know that modern air carriers (A300!) are still using mechanical gyros. But at the same time military drones do use MEMS gyros/accelero/magneto/gps. I used to think that mechanical watches are replaced by very many times more accurate digital watches, which in turn replaced by smart phones. I am just think aloud some brainstorming ideas. Sorry for typos and unorganized thoughts. – tlfong01 39 mins ago   
  • 1
    And in case what the Wikipedia says is true, ie mechanical coil spring sensors have low noise level compared to piezo MEMS gyro/accelero, we can perhaps use a hybrid approach, combining the cheapie but miniature 801 type sensor, augmented with more noisy MEMS but digitally filtered. imgur.com/gallery/leMnH1c. – tlfong01 29 mins ago   
  • Thanks for the insight @tlfong01. For what this is worth, I’m looking to detect and analyze seismic wave-forms (specifically surface-waves) that usually have comparatively long periods associated with them (e.g. 5 – 20 seconds). Could these sensors you refer to manage that kind of low-frequency sensitivity? Also, I’d really like to know more – if possible – of HOW to connect a geophone (or a similar sensor device) to a RP. – Nathan Benton 19 mins ago
  • *** Errata ***: I forgot that my answer about 801 vibration sensor has been deleted. This is a copy the essential parts of the answer about the vibration sensor I mentioned in the answer of vibration: penzu.com/p/484bcd9a. – tlfong01 12 mins ago   
  • Hi @Nathan Benton, Ah yes, you are right in pointing out that your signal frequency is VERY LOW 5~20 second period (of order 0.01 Hz). I happened to once played with low frequency brain wave (Alpha Beta etc), of range 1 to 20 Hz. Of course you frequency range is one order smaller. My brainstorming idea is to use “long mechanical coil springs or flexible blades” perhaps 12′ long, with MEMS gyro/accelero attached at the end of the long spring/blade. A similar method is to use sort of long arm pendulums, also with MEMS gyro/acceleros at the end. Bed time. See you later. Cheers. – tlfong01 1 min ago   Edit   

Categories: Uncategorized

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: