Guralp Systems CMG-3T - Manual (Page 3)

Operator's guide
1 Introduction
The CMG-3T is a three-axis seismometer consisting of three sensors in
a sealed case, which can measure the north/south, east/west and
vertical components of ground motion simultaneously. Each sensor is
sensitive to ground vibrations in the frequency range 0.003 – 50 Hz, a
broadband frequency response made possible by advanced force-
balance feedback electronics. Because of this wide response range, the
3T can replace many of the instruments conventionally used in a
seismic observatory; it also produces true pulse-shape records suitable
for modern earthquake mechanism analysis.
The 3T is designed for mounting on a hard, near-horizontal surface
well coupled to the bedrock. After levelling and orienting the case, you
can perform accurate adjustments internally by sending the
instrument control signals. These electronics allow it to compensate
for a tilt of up to 3 ° from horizontal.
Once levelled and centred, the 3T will begin operating automatically.
It outputs analogue voltages representing ground velocity on balanced
differential lines. These voltages can be recorded using a separate
logging device or digitizer. For testing and installation purposes, a
hand-held control unit is supplied which can monitor the instrument's
output.
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