EAI S102 Seismometer
OPERATING PRINCIPLES
The S102 is an inertial seismometer that measures ground motion with respect to an elastically suspended mass. Precision agate bearings and a hardened knife-edge pivot ensure long life. A linear, low noise RF displacement detector is used to sense the position of the reference mass with respect to the instrument housing. The reference mass is controlled in an electronic feedback loop by means of a moving magnet transducer. This feedback loop provides near critical damping of the system, resulting in an extended frequency response, and eliminating thermal noise, hysteresis and stiction normally associated with conventional mechanical systems. The transfer function of the S102 has nearly constant sensitivity to the vertical component of ground motion, and is similar to that of the moving coil sensors used in the World-Wide Standard Seismic Network.
Download the S102 Operating Manual (181k PDF)
(Requires Acrobat Reader)
SPECIFICATIONS
Mode of Operation: Vertical velocity sensing using inertial pendulum.
Outputs: 15 Vdc per mm/sec single-ended output; and 30 Vdc per mm/sec differential output. Inertial mass position 0 to 5 Vdc, single-ended output.
Maximum Output: +/- 8 Vdc
Frequency Pass-Band: 0.05 to 1.5 Hz
Damping Factor: 0.71, controlled through velocity feedback
Maximum Inertial Mass Excursion: +/- 1 mm, frequency less than 0.5 Hz
Temperature Range 40 to 90 deg.F with zero centering adjustment required; operation +/- 5 deg.F without readjustment.
Electronic Self-Noise Floor: Approximate USGS low-noise earth model 0.05 to 1.5 Hz
Sensor Housing: 7.5" high, 12" length, 7" wide
Calibration Port: A TTL control signal from the computer I/O port can be used to verify sensitivity.
Computer Interconnection: 10 meter cable (upto 100 meters optional) that user may connect to a multi-function A-D conversion adapter with a +/- 5 Vdc input range.
Leveling: Bubble level integrated into housing. Three leveling screws on base.
Reference Mass Positioning: Adjustment by an externally accessible adjustment screw (Required during initial setup and at about 6 month intervals.
Power Pupply: UL approved wall plug-in unit requiring 115 VAC, single-phase 50 to 60 Hz
CONNECTIONS & SOFTWARE

Data Acquisition:
A 30 foot interface cable is provided with the S102 to connect to a data acquistion card. Both single ended and balanced outputs are available. The S102 output voltage is compatible with most 12 or 16 bit digitizing/data acquistion cards (+/- V full scale) for PC and Macintosh computers. EAI can supply suitable data acquistion cards, or will advise the user of suitable units.

Software options to record and display data:
PC: EAI can supply software programs written in QuickBasic which enable data acquisition, storage and display of current seismic records. Existing files can be displayed and printed for later review. There is no additional cost for the software. Contact EAI for additional data acquisition options, or assistance with developing custom software.

Macintosh: Educational institutions may request a copy of MichSeis software from Dr. Lawrence Ruff at the University of Michigan, Department of Geological Sciences, C.C. Little Building, Room 2538, Ann Arbor, MI 48109-1063. MichSeis software is multitasking; allowing data acquistition and storage and display of current data, as well as viewing and manipulation of previously stored seismic data files. Networking and sharing of data files via modem is also supported. Educators may also consider joining the network of S102 seismic stations which have been established to promote educational use of seismometry.

ENGINEERING ACOUSTICS, INC.
406 Live Oak Blvd
Casselberry, FL 32707
PH: (407) 645-5444
FAX:(407) 645-4910

sales@eaiinfo.com
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