User's Manual

Connecting external sensors and systems
Page 31
7.2.7 RS232 ports
The extended sensor interface provides two non-isolated RS232 interfaces for connection of external
equipment. These ports are available via the Sensor 1 connector described in
Table 2.
The port operates at 38,400baud by default. The data types accepted are determined by the configuration of
the sensor interface.
RS232 port 2 shares hardware with the SDI-12 interface described in section 7.2.8 and is not available if the
SDI-12 interface enabled by configuration.
7.2.8 SDI-12 interface
The extended sensor interface provides an SDI-12 for interface to external sensors supporting this bus. The
SDI-12 interface is available via the Sensor 1 connector as described in
Table 2. The Sensor Interface operates
as an SDI-12 data recorder. The electrical interface consists of three connections:
● A serial data line
● A ground line
● A 12-volt line (used to power connected sensors)
For further information on the SDI-12 interface please refer to the specification available at
http://www.sdi-12.org/. Note that the 12V supply line is not provided by the sensor interface.
7.2.9 Relay drive output
The extended sensor interface provides an open drain relay drive outputs that default to the normally open
state. The outputs are capable of switching 100mA at 12VDC or 50mA at 24VDC; a circuit diagram of the output
driver is provided in
Figure 16. The relay drive output is available via the Sensor 1 connector as described in
Table 2..
Figure 16 Relay drive output reference circuit
7.2.10 Input voltage monitor
The Sensor Interface has the facility to measure the incoming power supply voltage. This can be used to
provide a measurement of the charge state of a battery supply to the transceiver. The voltage measured can
be included in transmitted AIS measurements if so configured. No additional connections are required in order
to make use of this facility.
From processor
RELAY_DRIVE
10K
100R
GND
GND
BSP75NTA