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Gantry Velocity: Quick Start Guide
Version 1.0; pending approval; Version 372 – A. de Loach


RUNNING A SAMPLE

For split core sections, velocity is measured in the X-axis with the vertical caliper transducer, and Y- and Z- axis using pairs of piezoelectric transducers (bayonets). Discrete samples are only measured on the caliper. The orientations shown in Figure 1 below, apply to discrete samples as well section-halves.

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The "Staus" 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 if this happens. If evrything is uploaded you are done, and can prepare the station for the next sample.
Once your finished uploading it is always a good idea to check your 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 autopicked first arrival wave. It will display the value in the "Velocity – Auto" box (see Figure 3) and display the autopick location line (Figure 12). If either of these do not look good, the following steps A, B, and C are suggested, in that order.


A) Autopick


The program's method of picking the first arrival wave out from the rest of the signal is a multi step process. Though simple enough, it requires greater detail then needed to run an experiment. For more information on how an autopick is made, see the user manual or ask the Physical Properties Technician. To evaluate the autopick velocity, you need to look at two graphs.
Autopick location lineThe 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 autopick of the first arival 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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Once you have adjusted the threshold and got the autopick 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 autopick 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)


The typical allowable deviation is 1% for the caliper and 0.5% for the bayonets. There will also be differences based on temperature, especially for water and aluminum. If the standard values are out of this range, ask a technician to help calibrate the instrument.


Viewing Your Data


To view your data, or most data around the lab, you can use the LIMS Online Report Portal (LORE) or the LIMS data viewer (LIVE) through a firefox browser. It is good practice to once a core or after each upload to check that your data has made it into the databse.
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.

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Figure 16. LORE, with P-Wave caliper data downloaded by hierarchy search.


Calibrating the PWV CALIPER


Procedure-
To begin calibration for the PWV select the "Caliper Piece X-Axis"
Click on the "Stations" tab to access the drop down menu, then click on "Calibrate Calipers".
Enter the Aluminum width- 30 mm, place Aluminum Standard (30mm) on the transducer.
Close transducers slowly
Click "Laser Offset" tab (blue)
Aluminum Standard field should be 6295.00
Click "Determine System Delay" tab (purple)
Adjust "threshold" till the redline on the graph is at first arrival point
The Velocity should be very close to 6295.00. If so, then "Accept Changes".