Tweet
http://njsas.org/projects/tidal_forc...ker/index.html
This is an amateur scientist-friendly design for an inexpensive vertical seismometer and gravimeter, based on a high-Q magnetic spring combined with force feedback, using optical displacement detection, and all mounted within a magnetically shielded isothermal enclosure.
************************************************** ****************
This instrument, which I call the "Hi-Q", will work as either a teleseismic vertical seismograph or as a gravimeter. Its virtues are that it is relatively small, inexpensive, and easy to build. My design utilizes a very high-Q magnetic spring suspension in combination with active magnetic feedback in an isothermal enclosure to give a frequency response that extends to DC, making it also suitable for use as a gravimeter, able to see the daily background fluctuations in earth tide.
The only real problem with a gravimeter being used as a seismometer is that seismometers are designed to be so sensitive to vertical acceleration that slow drift and earth tides are likely to throw the readings off scale. A seismometer usually looks for the smallest possible acceleration changes, Since gravity is physically the same as acceleration, gravimeters are merely versions of seismometers with an infinitely long period response. My instrument is capable of recording acceleration or gravitational data at a fixed location for long periods of time with minor adjustment. My instrument works to detect teleseismic events that match known events recorded by official seismic stations.
This is an amateur scientist-friendly design for an inexpensive vertical seismometer and gravimeter, based on a high-Q magnetic spring combined with force feedback, using optical displacement detection, and all mounted within a magnetically shielded isothermal enclosure.
************************************************** ****************
This instrument, which I call the "Hi-Q", will work as either a teleseismic vertical seismograph or as a gravimeter. Its virtues are that it is relatively small, inexpensive, and easy to build. My design utilizes a very high-Q magnetic spring suspension in combination with active magnetic feedback in an isothermal enclosure to give a frequency response that extends to DC, making it also suitable for use as a gravimeter, able to see the daily background fluctuations in earth tide.
The only real problem with a gravimeter being used as a seismometer is that seismometers are designed to be so sensitive to vertical acceleration that slow drift and earth tides are likely to throw the readings off scale. A seismometer usually looks for the smallest possible acceleration changes, Since gravity is physically the same as acceleration, gravimeters are merely versions of seismometers with an infinitely long period response. My instrument is capable of recording acceleration or gravitational data at a fixed location for long periods of time with minor adjustment. My instrument works to detect teleseismic events that match known events recorded by official seismic stations.
Comment