Inside the 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).
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Issue G - November 2019
