Nanometrics TC120-PH1, User Manual

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Chapter 4
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Input and Output Signals
Trillium Compact User Guide
16889R5

2014-03-04
28
The first equation is implemented mechanically in the Trillium Compact through the
orientation of the individual axes. The second equation is implemented electronically
when the Trillium Compact is in XYZ mode.
Alternatively, seismic data can be digitized with the Trillium Compact seismometer in UVW
mode and the transformation to horizontal and vertical signals being implemented when
the data are processed. For example, UVW mode is particularly useful for the calibration of
the transfer function of individual axes.
To account for the source impedance, see Table 9-1 “Ground motion response nominal
parameters for 120 s models” on page 46 and Table 9-2 “Ground motion response nominal
parameters for 20 s models” on page 47.
4.2 Serial RS-232 Communications
The 9600 baud serial communications interface is provided on the Rx and Tx signals of the
connector, where the DGND serves as the ground reference for the serial link.
A Trillium Compact automatically senses when valid serial communication on the Rx line is
being received, and turns on the Tx line to transmit. The Rx and Tx signals share pins with the
CTRL and UVW control inputs. Care must be taken to ensure that the UVW/TX line is not
being simultaneously driven by the digitizer/data logger. When serial communications are
occurring on the Rx and Tx lines, the control line signals CTRL (or SP/LP) and UVW that share
these pins are not effective. For more details, see Section 4.3 “Digital Control Input Signals”
on page 28, Section 10.1.1 “Pinout for 14-Pin Trillium Compact Connector” on page 51,
and Section 10.2.1 “Pinout for 16-Pin Trillium Compact Connector” on page 56.
4.3 Digital Control Input Signals
A Trillium Compact has two digital control input signals: UVW and CTRL. UVW changes the
output mode (which is XYZ by default) to UVW mode. By default, CTRL enables the
calibration function. You can reconfigure the CTRL control line to activate short period
mode (the default is long period mode) instead. The seismometer will respond to changes
in the state of the control signal within 5 s.
Each input is optically isolated from the input voltage, the output signals, and the
calibration input signals. Therefore, signals applied to these pins must be referenced to
DGND rather than ±PWR or AGND.
All of the control input signals are active-high signals. See Table 10-1 “Pinout for 14-pin
Trillium Compact connector” on page 51 and Table 10-6 “Pinout for 16-pin Trillium
Compact connector” on page 56 for details. All inputs can tolerate at least ±15V except
for UVW/TX which can tolerate voltages from –7 V to +15 V. The CTRL and UVW control lines
(1) Long period mode is the normal mode for collecting seismic data. However, you may want
to use short period mode when bench-testing the Trillium Compact, such as by tilting the
seismometer to see the response of the mass position outputs. When in long period mode,
the mass positions ramp very slowly and changes due to tilt may take several minutes. In
short period mode the mass positions respond within a second, allowing you to watch the
effects of tilting the seismometer.
(2) The UVW/TX input control signal is disabled when the seismometer is transmitting serial
communications because this pin is used as the RS-232 serial Tx output signal. For more
information on serial communication with a Trillium Compact, see Section 4.2 “Serial RS-232
Communications” on page 28 and Chapter 6 “Configuring Serial Communications.”