Guralp Systems CMG-3TB - Manual (Page 68)

CMG-3TB
Again, you can use the BUSY LED to monitor the progress of
unlocking.
1. The instrument checks to see whether the vertical mass is
locked, and unlocks it if necessary.
2. The vertical mass is centred by applying pulses to the motor.
This stage is often very short, since the vertical mass is locked
near its central position.
3. The instrument checks the N/S sensor and base, and unlocks the
sensor.
4. The N/S sensor base is tilted to its level position. This process
takes rather longer. At some point during this stage, the mass
may flip to the other side (as seen in the green trace.)
5. The N/S sensor mass is centred by applying pulses to the motor.
This stage will take longer than stage 2, since it must move the
mass all the way from its end stop. As the mass nears the centre,
the control circuit spaces out the pulses.
6. The E/W component is checked and unlocked.
7. The E/W sensor base is tilted to its level position as in step 4.
8. The E/W sensor mass is centred as in step 5.
After unlocking, the instrument automatically performs a round of
centring (see below).
68 Issue C