STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Demonstration, Transmit a range of values between 0 and 90".
MWD and LWD 943
Bit 1 1 1 1 1 1 1 1 1 1
Value 45 22.5 11.25 5.62 2.81 1.40 0.70 0.35 0.17 0.08789
Word 1111111111 = 89.91"
Word 1011011001 = 64.06'
Word 0001100111 = 9.04"
In another technique, each bit represents a power of two in a given word.
The highest number that can be transmitted is
as well as zero.
The smallest value that can be transmitted for a full scale of 90" is
90/1024 = 0.08789"
Each bit has the following numerical value:
Bit 29 2x 27 26 25 24 23 22 21 20
Value 512 256 128 64 32 16 8 4 2 1
For example, to transmit 64.06", the numerical value is
64.06,/0.08789 = 729
We will have one ''29" bit: 729 - 512 = 217
one Y7" bit: 217 - 128 = 89
one 'Y" bit: 89 - 64 = 25
one Y4" bit: 25 - 16 = 9
one 'Y" bit: 9 - 8 = 1
one "2°" bit: 1 - 1 = 0.
The word would be 1011011001 = 729. This is the same binary word as found
previously. In each technique the accuracy is 0.08'789" for a range of 0 to 90".
The rounding must be done the same way when coding and decoding.
Example 7: Mud Pulse Telemetry-Positive
Pulse Calculations
A positive pulsing device has been designed as shown in Figure 4-255.
1. Compute the pressure loss when the puppet valve travels from 0.2 to 0.5 in.,
where 0.0 in. is the fully closed position, for each 0.05 in. for a flowrate
of 400, 500 and 600 gal/min, and for a mud weight of 10 Ib/gal. The
nozzle equation is
Q = c A
i;"y
*144*g, *dP
(4-186)