Chapter 2
Performing a Posthole Installation
Trillium Compact User Guide
16889R5
2014-03-04
13
2.3 Troubleshooting Your Installation
It is normal to see spikes in the horizontal channels of a Trillium Compact as the seismometer
settles after installation. However, if these spikes do not diminish after a few days, there may
be a problem with the installation and the site should be visited to determine the cause of
the spikes.
lists common types of noise, including horizontal spikes, that may occur and
reasons why the noise may be present.
Table 2-1
Types of noise and possible causes for posthole deployments
Noise Type
Possible Cause
Spikes on the horizontal channels
There is unstable soil around the seismometer.
There is a force pulling on the cable.
Continuous low frequency
wander (random noise, larger on
horizontal channels)
The hole is not sealed and air drafts are causing
temperature fluctuations.
Spikes on the vertical channel
Usually due to electrical system noise. For example, power
supply noise from a battery charging circuit, or interference
from a strong magnetic or radio source that is nearby.
The mass positions are large, but
slowly trending towards zero, and
one or more of the main velocity
outputs has an offset on the order
of several volts.
The Trillium Compact is powered and not level or was
powered during levelling
When a Trillium Compact is left powered while not level, it
can take as long as a few hours for the unit to recover after
levelling. More importantly, when in this state, the unit is
unresponsive to ground motion. For short-term deployments
or when immediate confirmation that the sensor is working
properly is required, briefly setting the seismometer in short-
period mode allows the unit to recover immediately and
produce ground-motion recordings.
For fast recovery after levelling do one of the following
• Leave the sensor un-powered until after it is level
• Power cycle the unit, which momentarily puts the unit
in short-period mode during start up
• Access the user interface, put the unit into short-period
mode, and then immediately return it to long-period
mode (see
Section 7.3 “Seismometer Control”
• Use the control lines on the digitizer to briefly put the
unit into short-period mode, and then return it to long-
period mode
