Guralp-systems CMG-3ESPCD Manual de usuario descargar pdf (Pagina 80)

CMG-3ESPCD Digital Broadband Seismometer Inside the 3ESPCD

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).

7.1.2.3 CENTRE

This command re-centres the masses. If the masses are clamped, or if the

sensor mass positions do not exceed ± 1.2 V, the CENTRE command does

nothing. Otherwise, it attempts to zero the output of the vertical, N/S and E/W

sensors in sequence by exerting small extra forces on the boom.

For the vertical sensor, a motor-driven adjuster presses a small spring lever

against the boom until the mass position sensor indicates an offset close to

zero. In the case of the horizontal sensors, the sensor frame is tilted on its

base plate. Again, the controller monitors the mass position sensor and stops

the centring process once it reaches its lowest offset.

This graph shows a typical centring process:

MAN-C3E-0002 80 Issue B - November 2013

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Guralp-systems CMG-3ESPCD Manual de usuario Pagina 80