Table 4-4: Ideal Twisted Pair Characteristics For Successful Communication - Teledyne 440 System Manual

The SDC10 uses the 15-way D-Type labelled 'COMMS FROM SEP 'to communicate with the 440 SEP.
This connector is internally linked to 'COM1' used by DeepView to establish communication with the
440 SEP. There is no requirement to make an external connection to link the SDC10 and 440 SEP
comms.
The standard communication link between the SDC and the sub-sea installation of the 440 System
uses RS232 communication as default. However, it is selectable between RS232, 2-wire 20 mA
current loop and 4-wire 20mA current loop.
❐
RS232
This is a 3-wire link suitable only for communication over distances up to 15 metres. You may use
this method to transmit data to the survey control room using the ROV multiplexer and an existing
data link to the survey control room.
There are two further methods that you may use to establish successful communication between the
SDC and the sub-sea components of the 440 System:
❐
2-wire 20mA current loop
If the umbilical cable is of good quality, experience has shown that you may use this communica-
tion method successfully through transmission distances up to 1000 metres. To ensure reliable
communications through the umbilical, select a twisted pair that has the following characteristics:

Table 4-4: Ideal twisted pair characteristics for successful communication

Twisted pair characteristic
Overall resistance
Core size
Inter-conductor capacitance
You will need to reconfigure the SDC and the SEP to use this communication method. See
4.2.2.1 "Alternative Communication Methods" on page 4-11
❐
4-wire 20mA digital current-loop
You should select this method when the umbilical link to the ROV is longer than 1000 metres, or
where you cannot establish reliable communication using a 2-wire current-loop.
You will need to reconfigure the SDC and the SEP to use this communication method. See
4.2.2.1 "Alternative Communication Methods" on page 4-11
After you have made the necessary changes in the SEP and the SDC, perform a simple
communication check.
The Systems default parameters for communication between the SDC and the SEP are 9600 baud
with 8 data bits, 2 stop bits and no parity.
These communication settings are valid even when you use 2-wire or 4-wire cur-
rent-loop communications. This is because the SDC converts between current-
loop and RS232 communications through a special converter card. All communi-
DPN 402196 Issue 4.1
Ideal value
Less than 200
2
0.5 to 1.0mm
Less than 100pF per metre
for instructions to do this.
for instructions to do this.
NOTE
© Teledyne TSS
4 – Electrical Installation
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