Figure 5,
wiring
diagram for a
typical
CDP cable.
ductors.
There are a wide
variety of connectors used for
CDP cables, always with a large
number of contacts. Some CDP
connectors are hermaphroditic,
which means that rather than
having a male and female con-
nector, they are split into half
male and half female. The ends
arc identical and can be con-
nected to each other. The
cables are interchangeable and
reversible, which makes them
easy to handle in the field.
CDP cables can be ordered
with
different numbers of
takdouts and different numbers
of conductor pairs.
CDP cables are wired with the
connections staggered, so that
the cables can be connected
end-to-end to construct a cable
with many takeouts. Consider
the example in Figure 5 of a
CDP cable, with 24-pairs of
wires, a 48-pin connector on
Cable #l
2
1 4
-
2
0
1 2
24
-
3
2
22
34
-
3
8
-
0
-
2
34
46
4 2 - - - X - - 6
4 4 - - X - - - 8
4 8 - x - 1 2
each end, and six geophone takeouts indicated by
the “x”. The cable is wired so that pins 1 and 2 on
the red end are connected to pins 37 and 38 on t hc
other. The offset continues through the
sequence.
The result is that any cable may be connected to
any other to construct a cable on the
ground with
more takeouts. Similar patterns foollow for cahlcs
with more conductors and more or fewer takeouts.
How this works in the field is not obvious.
To illustrate, let’s consider just the
even numbers
(since all wires come in odd/even pairs).
Let’s
rearrange the positioning of the wires in
the
cable
drawing (the cable does not change, just the
arran-
gement of wires in the drawing), and
string four
cables together, as in Figure 6.
This combination of four cables makes a cable
with 24 takeouts, similar to our 24-channel rcfrac-
tion cable. Note that you could pick up the Icft
cable, reposition it on the right side, even
reverse
it end-for-end, and have exactly the same pin con-
nections. This is quite remarkable, and
extrcmcly
convenient.
Some CDP connectors will have alphabetic char-
acters rather than numbers to designate
pins.
Cable X2
-
3
2
22
34
28
40
34
4 6
36
3 8 - - - - x - 2
4 2 - X - - 6
4 8 - x - 1 2
2
1 4
1
1
6
1 2
24
Cable
2
-
-
2
3
2
-
-
6
-
x
-
2
4 2 - X +
4 8 - x - 1 2
2
1 4
1
-
2
2
1 2
24
1 2
26
22
36
Figure 6, Wiring
diagram
for a group Of
four CDP cables.
Cable
4 2 -X - 6
4 6 - - x - - - 1 0
4 8 - x - 1 2
2
1 4
1 2
24
22
34
32
44
-
4
6
Page 4
RS-%I24 & RS-120/48
Geostuff
