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The P-wave velocity gantry measures the speed at which ultrasonic sound waves pass through materials that are placed between its transducers; this includes section halfs, discrete samples, and mini-cores.
The three orthogonal sets of piezoelectric transducers allow the velocity to be determined in the X-, Y-, and Z-directions on working-half split-core sections. The P-wave bayonets (PWBs) measure the velocity along the core (Z-direction) and across the split-core face (Y-direction), and a P-wave caliper (PWC) measures the velocity perpendicular to the split-core face (X-direction) (Figure 1).
For discrete sample cubes, the velocity is measured along each of the three axes separately using the PWC; whereas, mini-cores are measured along the axis of the cylinder (X-direction). For discrete samples cubes and mini-cores, all sample information, including offset, is entered by the user???.
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- Make sure the sensors are clean.
- For section halfs, place the desired measurement location underneath the desired sensor. Make sure that the section is oriented with the blue end-cap towards the laser (Figure 2).
Figure 2.- Correct core position.
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- Select the measurement type. Seven different measurement configurations are available (Figure 3). Currently measures to whole round sections are not available.
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2. Depending on measurement, insert the bayonets or close the caliper onto the sample. Click the instrument motion buttons to slowly lower the transducers to the sample (Figure 4). The autoclose button functions for either the caliper or the bayonets.
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3. The program continually updates the velocity calculation and displays the value (Average of the sets of stacks) in the Velocity-Auto box (Figure 5).
Figure 5.- Data display on Velocity-Auto box.
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It also displays a signal graph with a red vertical auto-pick location line (Figure 6), where the program's algorithm has placed the first arrival wave.
Note: Typical slide bar settings are 100 for the stack bar and10mV for the threshold bar.
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The program will automatically calculate the velocity from its auto-picked first arrival wave. It will , display the value in the "Velocity – Auto" box (see Figure 35) and display and the auto-pick location line (Figure 127). If either of these do are not look good, the following expected results, follow steps A, B , and C are suggested, in that orderand C.
For further information see the User Manual or ask the Physical Properties Technician.
Figure 7.- Raw Stacked signal display with red line indicating auto-pick location.
A) First Arrival Picking
The
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signal graph has several different displays, all accessible by clicking on different tabs at the top.
To zoom on the graph, pause the program and click on the magnifying glass in the Graph Tools box, Figure 12.
To evaluate the auto-pick velocity, you need to look at two graphs.Auto-pick location line
The signal graph has several different displays, all accessible by clicking on different tabs at the top. Tip, you can zoom by pausing the program and clicking on the magnifying glass in the Graph Tools box, Figure 12. The first graph you need to examine is the stacked raw value ("RAW STACKED" tab), (Figure 11). Here you see the stacked measurements display with a vertical red line showing the location of the programs auto-pick of the first arrival wave. If the red line appears very near the first significant deviation from 0 on the Y-Axis, then the value is very likely reliable.
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Figure 12. Raw Stacked signal display with red line indicating auto-pick location.
Uploading Data to LIMS
- Click the MUT Icon. Log in using database credentials.
- Once activated, the list of files from the C:\DATA\IN directory is displayed. Files are marked ready for upload by a green check mark (Figure 7).
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