Chapter 4
Input and Output Signals
Trillium Compact User Guide
16889R5
2014-03-04
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are shared with the serial RS-232 port (see
). It is recommended that you use +12
V to activate these control lines and high impedance for deactivation.
4.4 Calibration Input Signal
The Calibration Input Signal is provided to allow for relative calibration of the seismometer
across frequency and over time.
Since the Trillium Compact is a symmetric triaxial seismometer, calibration is best performed
on the individual axes (UVW) rather than the horizontal and vertical outputs (XYZ).
Individual axis outputs can be digitized by placing the seismometer in UVW mode. For
instruction on how to set a Trillium Compact to UVW mode, see
4.5 State-of-Health Output Signal
The mass position output signal (MAXIMUM MASS POSITION) is provided to monitor the
effect of tilt and temperature on the spring that sets the rest position of the boom. As with
the calibration signal, this signal represents the state of the individual axes (UVW) rather
than the horizontal and vertical outputs (XYZ).
This signal represents the axis with the highest absolute mass position and its operational
range is ±4 V, with an optimal output of 0 V. A maximum mass position output signal greater
than ±3.5 V indicates that the Trillium Compact is no longer sufficiently level and may not
be providing useful seismic signals. Should this occur, visit the installation site as soon as
possible to level the unit.
4.6 Power Consumption
Following are power consumption scenarios typical of Trillium Compact seismometers:
Under normal operation (the unit is level, there is a low seismic signal, the unit has
settled for at least 30 minutes, and the RS-232 serial port is not transmitting), power
consumption for 120 s models is approximately 160mW and approximately 180 mW for
20 s models.
On start-up, power consumption may briefly surge to 1W.
Once level and operating normally, any additional power consumption above normal
quiescent is roughly proportional to the output signal and is largely independent of
mass position, providing the seismometer does not shift and is no longer sufficiently
level.
For a settled and level unit, a seismic signal that approaches the maximum clip level of
the seismometer may draw as much as a 0.8 W peak (the average power
consumption would be much lower).
For long cables, account for the resistive voltage drop due to the cable length and, if
necessary, increase the voltage at the source.
For example, 50 m of 24 AWG wire has a resistance of 4.2
Ω
in each direction. Therefore the
voltage drop due to the possible 100 mA startup inrush at 10 V would be 0.84 V. The supply
should also be able to sustain a 1 W peak output at a voltage that guarantees the
seismometer receives at least 9 V.