Guralp Systems CMG-1T User Manual

Page 25

Operator’s Guide CMG-1T Ocean Bottom
Seismometer

September, 1999, Issue C Section 6,
Page 1

LEVELLING PLATFORM INCLINOMETERS

The

levelling bowl drawing is given. Within the levelling bowl a 2 axis

inclinometer is installed to provide the tilt of the bowl in two independent axes
over the complete tilt range of the levelling bowl. The inclinometer outputs are
not linearly related to the actual tilt but calibration information is provided to
the user to establish the tilt of the bowl with reasonable accuracy. In actual fact,
in this application, it is not required that the inclinometer output should be
linearly related to the bowl tilt.

The inclinometer output varies over a voltage range of

4 Volts and the output

impedance of the circuit is <10

Ω

. The average power consumption of the

inclinometer circuitry is kept as low as possible. Normally the digital micro-
processor circuitry is used to switch the inclinometer electronics off after the
initial instrument installation. It is also accepted that it is unnecessary to re-use
the levelling bowl after initial setting up as the individual sensor components
themselves have

2.5

of levelling facility.