CiDRA SONARtrac PW VF-100 - Manual (Page 101)

20833-01 Rev 04 Page 7-7
7.3.1 COMM
This denotes the connection point for serial digital communications.
Either RS232 or RS485 communications is supported with baud rates
settable between 2400 and 115200 baud (8 bits, no parity, 1 stop bit).
The communications type (RS232/485) as well as the baud rate can
be set by the front panel keypad as listed in a later section of the
manual.
The RS-485 is the half-duplex two-wire type for multi-drop.
Note: If intermittent RS-485 communication problems are observed, it
may be necessary to put bus terminations of 120 ohms at the extreme
ends of the bus between COM+ and COM-. If necessary, follow best
practices in selecting the resistor and in connecting it reliably to the
bus.
Note: RS-232/485 is not available if Foundation Fieldbus
communication is present.
WARNING
EXPLOSION HAZARD - It is a violation of the Hazardous Area
ratings of the passive sonar meter transmitter to install the bus
termination resistor physically within this enclosure.
7.3.1.1 MODBUS
COMM connection also serves as the connection point for MODBUS
communications. The passive sonar meter transmitter supports both
MODBUS ASCII and MODBUS RTU formats. Refer to document Use
of Modbus
®
Protocol with Passive Sonar Meter Transmitters.
Note: MODBUS is not available if Foundation Fieldbus
™
communication is present.
7.3.2 PULSE
Pulse output is an isolated solid-state switch-closure-type output
which occurs between P+ and P- whenever conditions are met that
are determined by the pulse output settings within the transmitter.
The maximum applied voltage between P+ and local ground and P-
and local ground shall be within the range of +30V / -10V. The load
current shall be a maximum of 100mA. Typical turn on time is 1 msec.
Typical turn off time is 0.1 msec. Refer to the following figure and
example.