Chapter 5. Accessories
5.1 The hand-held control unit
This portable control unit provides easy access to the seismometer's control commands, as well as displaying the output velocity and mass position (i.e. acceleration) on an analogue meter. It takes input from the 26-pin connector at the bottom, and repeats it at the connector on the side for connection to further equipment.
The hand-held control unit can be sited up to 50 m from the breakout box.
5.1.1 The meter
The meter at the top of the unit allows you to monitor the voltage outputs of the instrument. Using the knob below, you can select either the mass position output or the velocity output, for each of the three components. There is also a RANGE switch allowing you to alter the sensitivity of the meter.
5.1.2 Calibration
The hand-held control unit can be used to calibrate the 3ESP. To activate the calibration relays, turn the knob to the component you wish to calibrate, and introduce a calibration signal on the CAL SIG banana sockets.
5.1.3 Control commands
You can use the hand-held control unit to centre the sensor masses. If your 3ESP includes the remote locking and unlocking option, you can also lock and unlock the masses through the hand-held control unit as described below; otherwise, you will need to lock and unlock the masses manually (see Section 3.3, page 9.)
To unlock the sensor masses on a sensor with automatic mass control, press the ENABLE switch down, and the LOCK/UNLOCK switch up simultaneously for 7 seconds. The BUSY LED will light. All three masses are unlocked, each in turn. The sensor then automatically moves on to centre the masses, during which time the BUSY LED will flash. When the BUSY LED goes out, the instrument is ready for use.
You should not attempt to move the instrument without re-locking the masses.
To lock the sensor masses on a sensor with automatic mass control, press the ENABLE and LOCK/UNLOCK switches down simultaneously for 7 seconds. When the BUSY LED goes out, the instrument is ready for transportation.
To re-centre the sensor masses on any 3ESP instrument, press down the ENABLE and CENTRE switches simultaneously for 7 seconds. When the BUSY LED stops flashing, the centring process has finished. You may need to initiate several rounds of centring before the instrument is ready; when no more centring is required, pressing the ENABLE and CENTRE buttons has no effect.
5.1.4 Outputs
The remaining banana sockets provide easy access to the output voltages of the instrument. For each component (vertical, N/S and E/W):
the left-hand two sockets expose the balanced differential outputs representing ground velocity, and
the right-hand socket exposes the mass position (acceleration) output.
Ground references for each of these voltages are provided at the bottom of the unit. Ensure that you do not connect either side of a differential output to ground.