Installing The Gecko Prism; Checking Sensor Operation - Gecko Compact Product User Manual

Installing the Gecko Prism

The Gecko Prism contains a very robust but very sensitive velocity sensor. Once the
seismograph is powered on, be careful not to move the sensor. Pressing the buttons to
control the unit should not send the sensor into a clipping condition. If you accidentally
knock the sensor and the signal levels start clipping, simply turn the unit off for a second
and then on again to quickly settle the sensor.

Checking Sensor Operation

After powering up your Prism, from the Home Screen it is recommended that you press the
Up button to view the signal values to check that the sensor starts up correctly.
About 20 seconds after power is applied, the Prism sensor will start up, one channel at a
time: East, North, then Up. Depending on the tilt, the signal values will shoot to a full scale
(positive or negative 8 million counts) and it will then begin to settle to the zero level. The
values may stay at the clip level for a few seconds as the sensor output has a greater range
than that of the recorder, but you'll soon start to see the numbers heading towards a zero
signal level. It takes about an hour for the integrators to settle and get close to the zero
level, and a few hours to settle completely - see 6+ hour recording below.
If one of the channel signals appears to be jumping around randomly, or if the sensor is
making a regular clicking or buzzing sound, turn the Prism off and on again after a few
seconds to restart the sensor initialisation routine. This state may occur if you knock or
move the sensor excessively during the initialisation period.
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