SSP Safety Simplifier, Руководство пользователя

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SSP North AB 30/08/2018 Manual V2f
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In Figure 13.4 nodes 1, 2, and 3 have direct radio contact
to each other, and 3, 4, and 5 have direct radio contact to
each other. This system will function. However, it violates
the some of the rules given in the beginning of this
chapter; node 1, 2, 4, and 5 only hear two other nodes.
This results in a less reliable system. It also violates the
rule that node 1 should hear the last node in the system.
The result of this is slower reaction times, and less
reliability.
Reliability
If node 3 loses power or stops radio communication due
to an error, no repeated information from node 1 will reach
node 4 and 5, and these nodes will leave the network.
This makes the network rely completely on node 3 to
work.
Reaction Times
The information from nodes 4 and 5 to nodes 1 and 2 will
be delayed by the repeating function of node 3, as it must repeat ”backwards”. This increases the
average reaction times in the system, but it does not increase the maximum reaction time.
Solution
To solve these two issues for the system in Figure 13.4, the system must be changed to follow the
rules given at the start of chapter 13.10.4. To achieve this, we can simply add a new node (node 6)
and put it next to node 3 (see Figure 13.5).
Now all rules are followed. Node 1 hears the last node in the system (node 6), and every node in the
system hears at least 3 other nodes, where one is always the previous node.
Figure 13.4: A system that relies on the
repeating function of node 3. If node 3 loses
power, nodes 4 and 5 will lose connection to
node 1 and will leave the network.
Figure 13.5: This system still relies on the
repeating function, but it has redundancy. If
node 3 stops transmitting radio, node 4 and 5
will still be able to hear node 1 and 2 via
node 6.