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Description: Need to put your finger on the pulse of the Earth? Did I just blow your mind? A geophone works by translating ground movement into voltage, which can easily be read by a microcontroller. The SM-24 geophone element is designed to offer the highest performance in seismic exploration based upon field-proven I/O Sensor technology. Low distortion, combined with excellent specifications, provide high-fidelity data. Basically, it's a super low frequency microphone for the ground.

Perfect for all of your 2-D & 3-D seismic exploration needs with bandwidth from 10 Hz up to 240 Hz

Features:

  • Tight specification, low-distortion vertical geophone
  • Extended spurious over 240 Hz, allowing full bandwidth at 2-ms sampling
  • Sensitivity of 28.8 V/m/s

Documents:

Comments 25 comments

  • Use these to set up a perimeter around your house and detect intruders!

  • Found another datasheet with readable graphs: SM-24

  • Before I spend $59 on a Geophone sensor, I would like to see a Sparkfun application circuit that will work with the Arduino!

  • Quote from above “A geophone works by translating ground movement into voltage, which can easily be read by a microcontroller”

    Please SF provide a schematic “application circuit” to interface your Geophone to an Arduino! It is not that simple to hookup to the Arduino A/D input. You probably need a precision OPA (24 bit) and some low pass cut off filters.

    http://arduino.cc/forum/index.php?topic=73149.0

    • rsp | last year * 1

      A good start for a geophone analog amplifier circuit is here. It’s very low power and highly sensitive. It’d be nice if somebody made a Seismic Shield product based on this circuit (wink wink nudge nudge).

      A simple geophone display, commonly used in ghost hunting equipment, is here. But it’s not very sensitive and doesn’t have an analog output.

      An example project that works well with the SM-24 sensor and has an analog output option is here.

      A lower cost (surplus) sensor that’s almost exactly the same size, but is a little less sensitive, can be found here.

    • Sure, you can hook it up directly if you want. It will work.

      What you suggest about precision op amps and an LPF is exactly how high-end seismic equipment is created.

  • I know this is just copied from the datasheet, but “Extended spurious over 240 Hz…”? Maybe “Extended spurious frequency rejection over 240 Hz…”?

    Could the geophone be combined with this or this to create a through-earth communication system? Does anyone know the sound velocity characteristics of concrete or limestone?

    • I’m having a bit of trouble reconciling the “bandwidth” (frequency response?) spec on this thing with the chart in the data sheet, which seems to show a pretty flat response from around 50 Hz through 1 kHz. I can see why you’d need a pretty good LPF between this thing and an A/D converter with a 500 Hz sampling rate.

  • Quote “Sure, you can hook it up directly if you want. It will work.”

    • I may have been a little too quick to type that.

      Since the arduino doesn’t have differential inputs, you’d have to inject a voltage ½ of your ADC reference voltage.

      I’d like to see a schematic too. I do have a few of my own personal schematics to interface these types of sensors to ADCs. Can I give my email address on here?

      • I don’t see why you couldn’t but remember, once it’s out there it is OUT there.

        • I agree and apologize for any possible disinformation. You can however hook these up directly to any ADC with differential inputs.

        • You could always use a photo sharing site and post the links.

  • Interesting, but I’d also like to see you offer an good quality (but really cheap!!) infrasound detector - i.e. down to around 0.02Hz.

    • I think those are better built than sourced, but suggest one and prove me wrong! Google for amateur seismographs and you’ll come up with some interesting designs.

      • Yeah, I’ve seen the amateur ones - trouble is I don’t have much skill at building. But as I can’t find a commercial one either (I hoped you might have come across one on your travels), it looks like I’ll have to build one. And then figure out how on earth to calibrate it…..

        • I see what you did there “How on Earth”. haha good one.

  • Perfect for keeping tabs on the mole men.

    • Tell you how old I am. Those little guys with that awesome ray gun (vacuum cleaner and a funnel) scared the daylights outta me! I was plenty glad when Superman got them back down that well! Makes me wonder, why did Hollywood decide you need $100 million special effects in kids films.

  • Overkill contact microphone?

    • Actually, according to the (incredibly low resolution) pictures on the datasheet. This appears to be a dynamic microphone. I wonder how well it would operate as a low frequency speaker?

      • It is a good quality magnet suspended by springs, surrounded by a coil. So, very similar to a microphone. Also these are similar to an accelerometer as well, just made for lower frequencies. I work with these all the time at my job.

        All you need to know is a few things to get started:

        Orientation… there are vertical and horizontal orientated versions which allow you to create a true tri-axial configuration using 3 geophones (1 vertical, 2 horizontal).

        Sensitivity. Volt/inch per sec.

        Frequency response. Most geophones are very linear from about 2-500hz. There will be a higher sensitivity in the geo’s sweet spot or natural frequency. You can also use a dampening resistor to make it much more linear in response but at the cost of sensitivity.

        • Cool, thanks for the info. I’ve seen some super powerful surface transducers with similar designs (except they had 2 symmetrical magnets, and a pair of voice coils). This would probably work great for recording explosions. Low frequencies travel right along the ground, so burying it shallow, or embedding it in something heavy on the ground would probably work well. I may have to look into getting one to play around with.

  • build a mesh network of office chair sensors with premptive flatulaence alarming…

  • DIY oil prospecting here I come!


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