STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

934 Drilling and Well Completions
The coding principle is given in Figure 4-245. Each angular value of azimuth,
drift and tool face is represented by ten bits. The practical “positive pulse”
system is slightly different. The “1” bits correspond to incomplete strokes of the
poppet valve as shown in Figure 4-246, making the system a slow phase-shiftkeying
system. Transmission rates of 0.2 or 0.4 bit/s are commonly used.
Marker pulse
t 0 1 1 0 1 1 0 0 0
\
Time
Figure 4-245. Principle of the coding of the positive pulse system. (Courtesy
Inteq-Teleco [105].)
0.2 biffsecond
0.4 biysecond
transmission rate
transmission rate
iioii pulse pressure
rise or fall
5 second fall --r - 2.5 second rise
5 second rise - Seco2?dseconds
pulse pressure ~
2.5 second fall
2.5 second fall - rise and fall
2.5 second rise ’1 or fall and rise
2.5 second rise J Over seconds
2.5 second fall - 1 - 1.25 second fall
over 2.5 seconds’-{
-, .25 second
‘{ 1 25 second rise
7.25 second fall
2.5 seconds {
) 5 seconds
Figure 4-246. Pressure waves used in the practical application of the
positive pulse system. (Courtesy Inteq-Teleco 11 051.)