CONNECTING A DPG
DPG Master/Slave configuration
0311385
Issue : April 1999
2-10
DPG Master/Slave configuration
It may be desirable to use two recording trucks in parallel, for example because of
geographical considerations. One recording truck is used as "Master" and the other as
"Slave".
Each recording truck is equipped complete with an acquisition system and a DPG.
One of the recording trucks is used as "Master" unit and the other as "Slave".
The DPG in the Master unit does not only perform the standard function (controlling all
DSDs and generating a reference signal), but it also controls the DPG in the Slave
unit. The "Master" DPG is configured as usual.
The DPG in the Slave unit needs to be configured with the "DPG-Slave" software
(loaded using the
toolsVeHci
software tool. See page 6-1). Once the "DPG-Slave"
software is loaded into a DPG, the function of the Slave DPG consists of generating a
reference pilot signal synchronous with the Time Break. A Slave DPG does not control
any DSD.
An example of Master/Slave configuration is shown in the diagram after the next
page, involving two recording trucks complete with a basic SN388 configuration.
The DPG synchronization method used in this standard configuration can be
extended to any acquisition system in use in the oil exploration industry.
The Slave DPG receives a DSD-like address (Crew #, Slave #) from the Master DPG.
On a Husky terminal connected to a slave DPG, the address of the slave DPG
appears as shown below:
Once addressed by the Master DPG, the Slave DPG acts as a DSD. It receives the t
0
parameter and t
0
Sync from the master DPG. On the first correct reception of a t
0
parameter, the DPG generates a signal (EXT_GO, 0/5 V, available on pins H and J of
the RECORDER connector) until the T0_SYNC signal arrives. The EXT_GO signal
can be used in the recording truck to initiate the 'Waiting for Time Break' sequence.
The time denoted T on the timing diagram below may vary from one recording system
to another.
In order to keep the time between the Firing Order and the Time Break to a minimum,
and to cause the Slave recording truck to initiate the 'Waiting for TB' sequence just
before the Sync is decoded, giving rise to the TB, you may need to adjust the number
of t
0
parameters to be transmitted, by modifying the 'T0 Repeat time' parameter. Try
different values until the best possible cycle is achieved.
DSD ADDRESS
page 1/1
CREW
:
3
3
x
4
4
SLAVE #
:
3
3
xx
4
4
The Slave number
may be 1, 2, 3 or 4.