The
Integrated Seismic System (ISS) can be based on any combination of
geophone, accelerometer and force balance accelerometers, in uni-, bi- and
tri-axial combinations. Each sensor type has different advantages in terms
of amplitude range, frequency range, reliability and cost. The tri-axial
configuration affords the most accurate estimates of source parameters. An
ISS International systems engineer would be happy to discuss the sensors
and configurations best suited to your application - so please
contact us at
your convenience.
Geophones are
usually the sensor of choice in most mining applications, because of the
low cost, large bandwidth and excellent reliability. ISSI manufactures two
kinds of geophones, with natural frequencies of 4.5Hz and 30Hz. The 4.5Hz
geophone has a usable frequency bandwidth of between 3Hz and 2000Hz but
must be installed to within 2 degrees of it's pre-set orientation with
respect to the vertical. The 30Hz geophone is omni-directional and can be
installed at any angle, with a usable frequency bandwidth of between 15Hz
and 2000Hz.
Electronic
frequency-dependent amplifiers may be used on these geophones. In this way
the 4.5Hz geophone achieves a lower frequency limit of about 1Hz, while
the 30Hz geophone may be extended down to 6Hz. The electronic extenders
are fitted in-line with the cable external to the borehole.
Accelerometers are
usually used where high-precision records of high-frequency events are
demanded. The accelerometer that ISSI manufactures has a bandwidth of
between about 0.2Hz and 2300Hz, with an extremely low intrinsic noise
level.
Non-seismic
Sensors
Any sensor with a slowly varying output which may be conditioned between
-5V and +5V or 4mA and 20mA may be monitored as part of the ISS. Strain
meters, creep meters, tilt meters and thermometers have all been
successfully employed. |
