Guralp Systems CMG-6T - Manual (Page 7)

Operator's Guide
positions whilst you adjust the offsets manually. If you prefer, you can
use the equivalent switch on a Hand-held Control Unit (see below.)
2.3.2 The hand-held control unit (HCU)
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.
The upper section of the HCU contains a simple
voltmeter for monitoring various signals from
the instrument.
•
To monitor the velocity outputs, switch
the dial to V, N/S or E/W LOW VEL
according to the component you want to
monitor.
•
To monitor the mass position outputs,
switch the dial to V, N/S or E/W MASS
POS. Whilst you are adjusting mass
position offsets, you should also switch
the instrument out of broadband mode by
switching the rightmost CENTRING
SELECT switch to 1 SEC VEL, or by
holding down the CENTRE button on a
breakout box.
•
You can set the range of the meter with the RANGE switch.
When switched to 10 V, the meter ranges from –10 to + 10 V (as
marked.) When switched to 1 V, the range is –1 to +1 V.
You can calibrate a 6T sensor using an HCU by connecting a signal
generator across the yellow and green CALIBRATION SIGNAL inputs
and setting the adjacent switch to ON. The sensor's response can now
be monitored or recorded, and calibration calculations carried out. See
section 3 on page 20 for full details.
You can zero the mass position offsets using the HCU. The normal
range of the mass positions is ±10 V; you should zero the instrument
if any mass reads more than around ±3.5 V when the sensor is
stationary. See section 2.4 on page 8 for full details.
The remainder of the HCU provides useful connections for each of the
signal lines from the instrument, for attaching to your own equipment
as necessary.
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