Sonavision Ltd.
Aberdeen, Scotland
Issue 6
2392-31-0008
Page 9 of 19
The CPU board controls all the communication with the surface control unit
and the control for the transmit and receive functions. The circuit contains a
powerful DSP controller which processes both analogue and digital signals as
required. In addition, The board contains the output driver components for the
stepper motor.
The PSU board provides all power supplies required by the electronic
modules via DC/DC converters. These units accept a single DC input in the
range 20 to 32 vdc and generates several power supplies for the electronic
circuits on the other boards. The unit is protected against reverse supply
protection and an automatically resetting fuse is incorporated into the supply
line to the system to reduce the possibility of damage due to other circuit
faults.
The PSU board also contains the telemetry driver circuits which interface to
the surface control unit. Three types of communications protocol are provided
for a variety of situations. These can all be selected by jumpers on the board.
RS485 2 Wire - Most suitable for long umbilical cables with a single screened
twisted pair for sonar data.
RS485 4 Wire - Suitable for long cables where two screened twisted pairs are
available or for certain types of data multiplexers built into larger ROV's.
These are usually based on Fiber Optic Technology.
RS232 3 Wire (RXD, TXD & GND) - Suited for systems with built in data
telemetry systems which require RS232 protocol. This protocol is not suitable
for driving long cables but may be used in test installations with cable lengths
limited to a few tens of metres.
The line drivers and receivers are optically isolated from the rest of the sonar
electronics to reduce the possibility of interference and ground loops. A high
value bleed resistor links the supply for the communications and the sonar
electronics to reduce the possibility of static voltage build up on the telemetry
lines.
The Housing is a pressure vessel which attaches to the end cap and seals the
electronics at one atmosphere against water ingress. It is fitted with an
IMPULSE 6 pin male connector for interface to the vehicle electronics.
The housing is secured to the end cap by a pair of seal screws which locate
onto studs on the internal chassis. The seal screws have piston seal O rings
to maintain water sealing.
Section 2.0 SYSTEM INSTALLATION
2.1 INTRODUCTION
Section 2.3 details how installation of the sonar unit should be carried out
assuming the sonar unit is to be installed on an ROV, with power being
supplied locally to the sonar unit and communication being connected via an
umbilical. This is the conventional mode of operation for this unit.
Alternatively, power can be supplied from the surface control unit through a
multi-conductor umbilical cable. In this case, ensure that voltage drop in the
power conductors is kept to an absolute minimum (2vdc maximum
recommended).
