Did you know your DTX CableAnalyzer
can tell you whether you have water
in your cabling system?
In this real-world example,
I'm going to walk you through
that process and diagnostics.
And not only am I going to confirm
there's water in the cable,
I'm going to actually tell you
where that water is in the cabling system.
So in this example here we see
the return loss failed
with a margin of -7.7 dB,
that's a very significant failure.
Now, it just as before, we need
to check to see that return loss
is only the failure
and resistance is not the issue.
And when we look at the resistance here,
all four pairs are roughly the same.
So that indicates that we don't have
a DC contact resistance issue.
If one of these pairs
was higher than the other,
then we have a contact resistance issue
but we don't.
So I'm going to hit the EXIT key.
And go back down to return loss.
And I'm going to hit the ENTER key.
Now, normally at this stage in the game,
I would be telling you to find out
which is the worst-performing pair,
but when you look at this trace
there's something rather unique.
And what I'm going to do
is I'm going to zoom in, so I'm going
to press the f2 key,
and the right arrow key, and again.
When you look at this trace,
what you see is that all four pairs
are following each other,
they're almost identical.
Now, they're failing at the
lower frequencies, which, as in the
previous module, indicates
that we have a cable issue.
But when they're failing
exactly the same on top of each other
that tells me I have water in the cable.
At this stage in the game
there's no point in going on;
that cable's got to come out,
it's probably in the conduit and
you've got to find out how to
dry out that conduit.
If it's external, then you'd
be needing to look at an OSP cable.
Let's take this one step further.
I'm going to hit the EXIT key,
and I'm gonna go down to my
feature called HDTDR analyzer.
This is a return loss failure,
and so I should be able
to look down the cable,
see where the impedance mismatches are
and figure out where this water in the cable is.
I'm going to hit the ENTER key,
then I'm going to hit the f3 key,
and I'm going to hit it until I get to
pair 3,6.
I'm only doing that
because that's the shortest pair.
That'll give me the correct distance
to the fault, because, when you're
talking about measuring air to sheath,
that's done based on the shortest pair
in the cable.
Now, you'll notice that the cursor
has gone to 60.7 meters
and has shown an anomaly of -16.4.
That is really bad news,
I mean, just for the cable alone
we don't want more than -0.8%.
So when we see minus, what is it 16.4%,
something really dramatically is
going on at that location.
I'm going to hit the f2 key.
Press the right cursor key.
And again. And up.
And maybe up one more.
Just to give us a better picture
of what's going on here.
So what are we looking at here?
We see this down spike, and then
it comes back up, he goes along
and then we see a vertical spike
and it comes up, and it goes down.
When it goes down 16.4
and it comes back up,
it hasn't technically recovered.
What that is telling me is that
my impedance changed by roughly
16.4%. So, from this point on,
it's definitely not 100 ohms.
It's probably more like about 85 ohms.
And then when it gets to almost
the end of the link,
we get a positive number
and it comes back down again.
And that returns us to roughly about 100 ohms.
So, here's what we can do.
We'll take it off zoom mode.
We'll move the cursor to where it starts.
We'll set the marker,
and then we'll move to where it ends,
I would say roughly about there,
indicating that we have about 6.7 meters
of cable at the end of the link
which has water in it.
So, let's just recap that:
when you look at the return loss trace,
if you see all four pairs
following each other on the graph
at the lower frequencies
you have water in the cable.
When you look at the TDR,
you're looking for significant events,
and most the time when you have
water in the cable, a significant event
is going to be anything over minus 5,
minus 6, or plus 5, or plus 6%.