l
Three or more 1Zchannel refraction
cables
l
CDP cables with up to 96 takeouts.
For the RS-120/48, we recommend CDP cables
with up to 120 takeouts or four 24-channel
refraction cables (or 3 if not recording with a
gap).
Each of these possibilities is discussed below.
In general, the types of connectors used on the
geophone cables will be different than those on
the rollalong switch, and a set of adaptor
cables will be required. It is. common to mount
the seismograph and rollalong switch in a
vehicle, and to install the adaptor cables so
that the seismic cable connectors are on the outside
of the vehicle (the common name for this is an
“input panel”).
Most users purchase a set of input adaptor cables
already wired for the cables used. Geostuff can pro-
vide suitable adaptor cables as a separate item. For
systems purchased without cables, a set of mating
connectors is supplied with the rollalong switch.
Unless purchased with the system, you will need to
supply a pair of connectors to mate with your par-
ticular cable types. Appendii 1. contains wiring
diagrams for several popular adaptor cables.
We will use a convention that geophone group 1 is
located on the far left end of the cables, and group
96 (or 120) located on the far right end (left and
right are relative, depending on the position of the
operator).
3.1 Using 24-Channel Refraction Cables
Refraction cables with 24 takeouts can be used.
These cables should be reversible and interchange-
able, meaning that the wiring connections are the
same from either end of the cable. Consider Figure
Pin
Pin
No.
No.
1-w
4
7
4 - - - N
4 4
7
W
4 1
6 - - - - - - N
4 2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 3
W
4 4
N
4 5
3
4 6
4
4 7
N
-
Figure 1, 24-channel refraction cable.
wired to pins 1 and 2, and the far takeouts arc wired
to pins 47 and 48. Some cables use connectors with
alphabetic pin designations, but the principle is the
same. No matter which end of the cable is con-
nected to the seismograph, it looks the same. 12-
channel refraction cables are wired in a similar
manner.
For CDP surveys, you need at least two of these
cables and at least 48 geophones (or groups of
geophones). The rollalong switch is located in the
center of the line, as in Figure 2.
The output cable assembly from the rollalong
switch is connected directly to the seismograph (the
connectors are labeled channels 1-12 and 13-24,
do
not interchange them).
In the case of a 48-channel seismograph (with
up to
120 input stations), the optimum configuration is
to
have four 24-channel cables plus two extension
cables. You can work with just three cables, but not
while recording with a gap.
The rollalong switch is set to position’& which con-
nects stations 1 through 24 (or 1 through 48) to the
l., the wiring diagram for a refraction cable with 24
takeouts. The column of
numubers
on each side
represent the pin num-
bers used in the connec-
2 1 2 2 2 3 2 4
25 26 27 28 29 45 46 47 48
tor. The W and N
indicate the wide and
I
narrow
takeouts (or
RS-96124
positive and negative, or
red and black).
Notice that on either end
Seismograph
of the cable, the closest
(near) takeouts are
Figure
2, Cable
arrangement
with two 24-channel
refraction cables.
Page 2
RS-96124 & RS-120/48
Geostuff
