Guralp Systems CMG-1T User Manual
Page 13
Operator’s Guide CMG-1T Ocean Bottom
Seismometer
September, 1999, Issue C Section 2,
Page 1
2.
DESCRIPTION AND EXPLANATION OF THE MECHANICAL
SENSOR SYSTEM
A photograph of the overall construction and layout of the seismometer are
given here, together with some details of the individual sensors.
The horizontal and vertical sensors are based on a shared design, that of a leaf
spring suspended boom supporting a transducer coil, the boom and coil forming
the inertial mass. The boom consists of a solid machined beam which swings on
a frictionless hinge. The system has no spurious resonances below 140 Hz. The
vertical component instrument has a pre-stressed triangular support spring
which supports the weight of the mass. The horizontal component sensors have
un-stressed flat triangular springs, giving a natural period of about 1 second,
while the vertical component sensor has a natural period of about 0.5 second.
The effective mass is about 250g in each case. The small stiff springs and short
boom lead to a very compact design permitting the designer to incorporate three
instrument in a relatively compact case.