**WELLOG
****LOG
PRINT/PLOT RESOLUTION**

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**REVISED ****12-27-2006**

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**© ****WELLOG**** 2006**

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**The resolution of an acquisition system must be compatible with
the resolution of the printer or plotter that has been chosen for hardcopy.**

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**Can the printer/plotter used for presentation adequately resolve
the data captured by the acquisition system?**

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**How much acquisition system resolution is enough?**

**Here’s an example:**

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**Given:**

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**An HP Desk jet 930C inkjet printer or Printrex C930 Color Thermal printer
with an x and y (horizontal and vertical) pixel resolution of 300 Dots Per Inch
(300 x 300 DPI). Note also, other printers i.e. Printrex 820 DL/G and 840 DL/G
have a lower (200 x 200 DPI) resolution. **

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**An acquisition system having a 12 bit resolution (4096 digital
representations of a full span analog signal input).**

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**Horizontal pixel plotting considerations:**

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**The largest track combination is track 2 and track 3. According to
API standards that equals 4 inches. The number of possible display pixels over
the horizontal length of both of the two tracks is 4 inches x 300 pixels per
inch = 1200 pixels. The 4096 voltage levels divided over 300 pixels per inch
will require a horizontal track of 13.65 inches. It is impossible to display
all 4096 voltage representations within the 1200 pixels available. The
analog input signal must be attenuated by a factor of four. Then, four
or more voltage levels will be represented by one pixel position over the 1200
horizontal pixels. The resulting resolution is 1024 pixels over a horizontal
scale of 3.41 inches. When the presentation is made over a two inch track, it
is possible to see that the input signal would have to be divided by a factor
of 8. This scale will give a presentation over 1.7 inches and one pixel will
represent 8 different input voltage levels. **

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**A possible solution is to wrap the presentation. For the full 4096
bit levels to be presented over 13.65 inches the trace would wrap 3 times and
when using a 2 inch track, the trace would wrap six times. Logs having 6 wraps
are very difficult to read. It is difficult to keep track of how many wraps
have occurred. This problem can lead to errors in reading and interpreting
data. **

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**Vertical pixel plotting considerations:**

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**A number of possibilities exist for vertical plotting scales. Logs
can be printed in 1 inch per hundred feet, 2 inches per hundred feet, and 5
inches per hundred feet.**

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**With a sample rate of 10 samples per ft. the 1 inch per hundred
feet log produces 10 x 100/1 = 1000 samples per inch.**

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**With a sample rate of 10 samples per ft. the 2 inch per hundred
feet log produces = 10 x 100/2 = 500 samples per inch.**

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**With a sample rate of 10 samples per ft. the 5 inch per hundred
feet log produces 10 x 100/5 = 200 samples per inch. **

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*******Note this last scale is the only scale that this plotter is
able to define a pixel for every sample taken. **

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**The physical log presentation of a 10,000 ft. well would be 500
inches. That is 500/12 = 41.7 feet long. Looking at the presentation in terms
of sheets of printer paper 500/11 = 45.45 standard 11 inch sheets or if using
standard API 6.25 inch logging paper that’s 500/6.25 = 80 sheets.**

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**The 10 sample per inch example will require a plotter having a
1000 DPI capability. A pixel having resolution of 1/1000 ^{th} of an inch
is extremely small.**

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** ****Horizontal resolution answer:**

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** A ten bit acquisition system is adequate for all of the
above applications. A ten bit system gives 1024 bit positions over 4 inches x
300 DPI is acceptable with no loss of data. When using a 2 inch track, a
compression of less than 50 percent is a nominal compromise.**

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**Vertical resolution answer:**

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**Sample rates of five samples per foot is adequate in order to
present samples on 1 inch per 100 feet log without compressing much more than
40 percent of the samples.**

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**For answers to questions about printer resolution vs acquisition
system resolution contact info@wellog.com .**