P-Wave Quick Start Guide
Table of Contents
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Introduction
Running a sample
Supplementary Information
Evaluating Your Measurement
A) First Arrival Picking
B) Manual pick
C) Running a Standard as a QAQC Check
Viewing Your Data
Calibrating the PWV CALIPER
Credits
Archived Versions
The P-wave velocity station.
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Introduction
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 (Figure 1) 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).
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For discrete sample cubes, the velocity is measured along each of the three axes separately using the PWC
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; whereas, mini-cores are measured along the axis of the cylinder (X-direction)
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. For discrete samples cubes and mini-cores, all sample information, including offset, is entered by the user.
Velocity data generated from these sensors are part of the physical properties suite of shipboard sample measurements.
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Figure 1. Core section-half liner showing top of section and relative orientations.
Running a sample
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Procedures
Preparing the Instrument
CAUTION: DO NOT place anything, including samples, below the instruments before opening the program
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. The program will close all transducers upon startup, and
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CAN CAUSE SEVERE INJURY.
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Copy From SHMSL
Preparing Samples:
- 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 ).
- Place
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- a small piece of Glad Wrap at the measurement location to keep the sensors clean and the core free of contamination
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- (including
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- water).
- Place one or two drops of deionized (DI) water at any relevant sample
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- /sensor interface. It will improve the signal transmission.
- For discrete samples, place them
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- within the caliper transducers with the desired axis
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- oriented vertically
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- .
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Figure 5. Measurement Configuration Options
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Making a Measurement:
- Select the measurement type. Nine different measurement configurations are available (Figure ).
- 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 ). The autoclose button functions for either the caliper or the bayonets.
Note: For the bayonets,
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insert them
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until the entire sensor (the circular part of the black sensor dot) is
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within the sample. Stop before the bayonets make contact with the liner
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.
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Figure 7. Clean waveform indicating a strong/good signal.
- The program continually updates the velocity calculation and displays the value (averahe of the set of stacks) in the
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- Velocity
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- -Auto
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- box (
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- Figire ).
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- It also displays a signal graph with a red vertical auto-pick location line (Figure 7), where the program's algorithm has placed the first arrival wave.
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Note: Typical slide bar settings are 100 for the stack bar and10mV for the threshold bar.
- Click Save Data
Note: If the velocity is out of the expected range, or the pick location is not near or at the first arrival wave,
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contact the PP technician.
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- Save Your Data
- The
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- Section Information screen is displayed.
- Place the cursor in the SCAN field and scan the section label. SAMPLE ID and LIMS ID automatically fills. These ID tags contain information on expedition, site, hole, core, section number and length.
Additional entry field options are the LIMS and MANUAL tags.
- Check that the test offset data is correct for section halves
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- . If you are measuring a discrete sample, the offset is already in the database
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- .
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In the MUT directory window below, you can either upload the files individually with the "Upload" button in the bottom right of the window, or in the box next to it, check "Automatic Upload". Once the files have uploaded successfully, they will be cleared from the directory window, and a copy is saved to the computer's local drive in a folder titled "Archive." You should leave this program running in the background. Simply minimize the directory window.
NOTE, do not close the window with the "X", always use File → Exit or minimize. If you do accidentally close with the "X" you have to find the puppy icon on the expanded taskbar and double click it to re-open.
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Figure 10. MUT login window.
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The "Status" column symbol in the figure above, should be a green check prior to uploading. When uploading the figure will change a cylinder with a green dot. If there is an issue with the filename, or database connection, the symbol will appear as a purple question mark. Please ask a technician for assistance if this happens. If everything is uploaded, you are done and can prepare the station for the next sample. Once you are finished uploading data, it is always a good idea to check the data in the IODP database. Please see the supplementary information section on the next page for more information.
Supplementary Information
Evaluating Your Measurement
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 3) and display the auto-pick location line (Figure 12). If either of these do not look good, the following steps A, B, and C are suggested, in that order.
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The program's method of automatically picking the first arrival from the signal is a multi step process. For more information on how an auto-pick is made, see the user manual or ask the Physical Properties Technician.
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.
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- Click Save Data
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Figure 3. Program home screen. 
Figure 4. Section-Half loaded under caliper.
Figure 5. Measurement Configuration Options
Figure 6. Instrument motion buttons.
Figure 7. Clean waveform indicating a strong/good signal.
Figure 9. Sample Information window with relevant sample ID fields populated
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Figure 13. ABS Zoom display with threshold slide bar and uncorrected auto-pick location.
Once you have adjusted the threshold and got the auto-pick to the correct location, go back to the "RAW STACKED" or other raw displays and verify the red line is at the first arrival wave. If satisfied, you can now save your data. If the velocities and picks still don't look right, you have the option of manually picking the first arrival.
B) Manual pick
In order to do a manual pick, first pause the program. Now the "MANUAL PICK" display tab will be visible above the signal graph (Figure 14). Select that display; find the graph toolbox in the lower left corner of the display. If you need to zoom in, use the magnifying glass tool. Next, click on the crosshair tool on the far left side of the toolbox bar (Figure 14). Hover over the dotted yellow-green vertical pick line. When the icon changes, click and drag the pick line to the desired location and release. You will now see that the "Velocity –Manual" box has updated with the manually picked velocity. Both the auto-pick and manual pick velocities are saved simultaneously to the database when you upload.
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Figure 14. Manual Pick display with yellow-green manual pick location.
C) Running a Standard as a QAQC Check
If you are not confident that the gantry system is running normally, you can run one of our standards to verify the instrument is giving the expected velocities for the material.
We have three materials available as a standard. Aluminum and acrylic are for the caliper, and a core liner with D.I. water for the bayonets. The expected velocities for each are below:
Aluminum 6295 meters/sec (+/- 63 m/s)
Acrylic 2730 meters/sec (+/- 27 m/s)
Water 1480 meters/sec (+/- 7 m/s)
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With Firefox open, click on the toolbar link "LIMS Online Reports" or go to the "Download LIMS core data" link on the ship's homepage (Figure 15). Once in LORE, click through the search options and sample filters to find your data (Figure 16). You can leave the window open in the background and simply refresh next time you want to check your data.
LORE gives you a fast way to download core data from most lab systems aboard the JR. You can export directly to an Excel or .csv file.
Figure 15. Ship's Home page with links to LORE and core data.
Figure 16. LORE, with P-Wave caliper data downloaded by hierarchy search.
Calibrating the PWV CALIPER
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Credits
This document originated from Word document Gantry Velocity: Quick Start Guide Version 1.0; Version 372 written by A. de Loach (2017-12-16). Credits for subsequent changes to this document are given in the page history.
Archived Versions
P-Wave Quick Start Guide (*.pdf)
PWV_QSG_372.docx: A Word document of the Gantry Velocity: Quick Start Guide