| ??? 10/11/09 11:05 Read: times |
#169631 - have seen before Responding to: ???'s previous message |
Steve M. Taylor said:
point is that accelerometers are rubbish
CHEAP solid state ones certainly are ! I suppose a seismometer IS an accelerometer ! There's a lovely project which I've spent ages looking for that fits in a coke can, or nearly. http://tinkeringcaveman.googlepages.com/home Steve Something like ancient Chinesee earthquake sensors........... Steve M. Taylor said:
I have found this The following was sent to the SAS (SOCIETY FOR AMATEUR SCIENTISTS) Amateur Scientist's Forum email (see http://www.thesphere.com/SAS/) and the PSN mailing list. -------------------------------------------------------------------------- Greetings, This is my first message to this list so I apologize for being so negative, but here it goes... In the last SAS Amateur Scientist's Forum email (Vol 3 #1) I read two messages about this article, here are my thoughts on it. I think the April 1996 Scientific American article on a New Backyard Seismograph has been a big disservice to the amateur seismology community. If the article had been labeled as a strong motion sensor I wouldn't have any problems with it. I hope to get a hold of some of the IC sensor chips myself someday and make a strong motion sensor using these chips. The problem is these chips are designed to detect a car crash not the very small movements that most events make. Someone on the Public Seismic Network mailing list (see http://www.seismicnet.com/maillist.html) once calculated that it would take a local (under 100km) quake of magnitude 5 or larger before you would get a useful signal out of this type of sensor. If you do not live near active faulting you are not going to pick anything up. You will be spending a lot of time and money for nothing. If you do live in a place where you have large earthquakes (like myself, I live in the San Francisco Bay Area) this sensor should be your second sensor, first make a more sensitive seismometer like a Lehman or Shackleford-Gundersen. Even in areas with large events you can wait a long time between events that will be large enough to pick up. I have been recording local and teleseismic events for over 2 years with sensor in my house and monitoring USGS telemetry signals, and so far there have been only one event that I could barely feel. I would be surprised if this type of sensor would have pick up anything. One more thing about this type of sensor. Given that you will only be recording large local events I would suggest you have all of system/electronics on some sort of battery backup system or UPS. If the event is large enough you may loss AC power and loss the data before it can be stored. Now for some good news. You can pick up earthquakes at home. You just need to make a more sensitive device. Both the Lehman sensor (see July 1979 SA) or the Shackleford-Gundersen (SG) sensor (Sept 1975 SA) will record a lot more events then a sensor based on a ADXL05 accelerometer IC chip. This making the hobby of seismology a lot more enjoyable. I have found that the SG sensor design makes for a very good seismometer for recording teleseismic (distant) events. I have compared seismographs from my SG sensor to broadband commercial sensor, run by the Berkeley University near me, and am amazed at how similar they are. Not bad for a sensor that costs under $200.00 for the parts compared to a STS-1 or STS-2 Streckeisen seismometer costing a lot more (I think I read that they are around $10K). I hope to have a Web page showing the differences between the different sensor on the Redwood City PSN Home page soon. For more information on making a seismograph system please see my PSN home page at http://www.seismicnet.com. Regards, Larry Cochrane Public Seismic Network Redwood City, Cal USA Steve Yes,I had pointed that before... But When we talking about networked Accellerometer sensors for earthquake. Not one sensor(had pointed that also from circuit cellar) even big cars or trucks will made earthquake when pass nearby sensor or ~100m. I found that at least 8 poles acellerometer networked sensors for seismic activity and placed as far as we can. (but with economics rs-422/485 ~1.1km) The idea then copied by laptop/notebook manufactures to produced with accellerometer inside and "internet link"..I forgot the exactly branded. Thank's Jeckson Ben |
| Topic | Author | Date |
| Earthquake sensors with X-Y accelerator | 01/01/70 00:00 | |
| Sorry - was there a question? | 01/01/70 00:00 | |
| Seismograph | 01/01/70 00:00 | |
| Why is that? | 01/01/70 00:00 | |
| Oddly | 01/01/70 00:00 | |
| Phew! | 01/01/70 00:00 | |
| Noooo | 01/01/70 00:00 | |
| with accellerometer | 01/01/70 00:00 | |
| Why ? | 01/01/70 00:00 | |
| With Accellerometer below 100US | 01/01/70 00:00 | |
| Cheap - but useless? | 01/01/70 00:00 | |
| thinking of it | 01/01/70 00:00 | |
| on second thought | 01/01/70 00:00 | |
| Did I said networked accellerometer? | 01/01/70 00:00 | |
| Sensing | 01/01/70 00:00 | |
| laptop/notebook | 01/01/70 00:00 | |
| fundamental flaw? | 01/01/70 00:00 | |
| SEEK and ye shall find | 01/01/70 00:00 | |
| have seen before | 01/01/70 00:00 | |
| What's the point | 01/01/70 00:00 | |
what's the point? | 01/01/70 00:00 | |
| Read ? | 01/01/70 00:00 |