Nanometrics Trillium Compact User Manual page 50

Table 4-1 - Types of noise and possible causes for posthole deployments (Continued)
Noise Type
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.
Table 4-2 - Types of noise and possible causes for vault deployments
Noise Type
Spikes on horizontal channels
Continuous low frequency
wander (random noise, larger on
horizontal channels)
Spikes on the vertical channel
16889R10 • 2020-11-12
Possible Cause
The Trillium Compact is powered and not level or was powered
during leveling.
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 leveling.
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 leveling do one of the following
Leave the sensor unpowered until after it is level
l
Power cycle the unit, which momentarily puts the unit in
l
short-period mode during start up
Access the user interface, put the unit into short-period
l
mode, and then immediately return it to long-period mode
(see "Control Lines" on
Use the control lines on the digitizer to briefly put the unit
l
into short-period mode, and then return it to long-period
mode
Possible Cause
The feet of the seismometer are not locked.
l
There is a force pulling on the cable.
l
There is something touching the sides of the seismometer.
l
Insulation is missing or not well sealed, allowing drafts to
l
blow over the seismometer.
There are forces, such as wind, acting on the installation.
l
Usually due to electrical system noise. For example, power
l
supply noise from a battery charging circuit, or interference
from a strong magnetic or radio source that is nearby.
Chapter 4 - Post-Installation Activities
page 65)
Page 50