Guralp Systems CMG-3T - Manual (Page 12)

CMG-3T
If you cannot easily see the pointers, you should align the
sensor using the north arrow on the handle. However, the
alignment of the handle with the sensors inside is less accurate
than the metal pointers, so they should be used wherever
possible.
5. The top panel of the 3T includes a spirit level.
Level the sensor using each of the adjustable feet of the
instrument in turn, until the bubble in the spirit level lies
entirely within the inner circle. (The instrument can operate
with up to 2° of tilt, but with reduced performance.)
The feet are mounted on screw threads. To adjust the height of a
foot, turn the brass locking nut anticlockwise to loosen it, and
rotate the foot so that it screws either in or out. When you are
happy with the height, tighten the brass locking nut clockwise
to secure the foot. When locked, the nut should be at the bottom
of its travel for optimal noise performance.
6. Connect the sensor to a breakout box, or a Güralp digitizer if
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