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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 halves, 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. Mini-cores are measured along the axis of the cylinder (X-direction).

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1. Double-click the MUT icon on the desktop (Figure 1a2a) and login using ship credentials. For more information on data uploading see the "Uploading Data to LIMS" section below.
2. Double-click the IMS icon (Figure 1b2b). IMS initializes the instrument and checks the movement of the the three instruments. Once initialized, the logger is ready to measure the first sample.

Figure 12. - (a) MUT Icon. (b) IMS Icon.

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1. Make sure the sensors are clean.
2. For section halves, 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 23).

Figure 23. - Correct core position.

3. Place a small piece of Glad Wrap at the measurement location to keep the caliper sensor clean and the core free of contamination (including water).

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1. Select the measurement type. Seven different measurement configurations are available (Figure 34). Currently measures to whole round sections are not available.

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Figure 34. -  Measurement Configuration Options

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2. Depending on which measurement, insert the bayonets into or close the caliper onto the sample. Click the instrument motion buttons to slowly lower the transducers to the sample (Figure 45). Alternatively, use auto close. Auto close button functions for either the caliper or the bayonets.

Figure 45. - GANTRY motion buttons.

Note: Insert the bayonets until the entire sensor (black dot) is within the sample. Stop before the bayonets make contact with the liner.

3. The program continually updates the velocity calculation and displays the value (Average of stack set) in the Velocity-Auto box (Figure 56).

Figure 56. - Data display on Velocity-Auto box.

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Program also displays a signal graph with a red vertical auto-pick location line (Figure 67), 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.

Figure 67. - Clean waveform indicating a strong/good signal.

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The program will automatically calculate the velocity from its auto-picked first arrival wave, display the value (Figure 56) and the auto-pick location line (Figure 78). If either of these are not expected results, follow steps A, B and C.

Figure 78. - Raw Stacked signal display with red line indicating auto-pick location.

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The signal graph has several display options, all accessible by clicking on different tabs at the top. To zoom on a graph, pause the program and click on the magnifying glass in the "Graph Tools" box, Figure 78.

To evaluate the 'auto-pick velocity', you need to check the 'Autopick location line' (red line):

1. Go to RAW STACKED tab (Figure 78): Here you see the stacked measurements display. If the red line appears near the first significant deviation from 0 on the Y-Axis, then the value is likely reliable. However, if the 'auto-pick location' is off, or the velocities don't seem right, you may need to adjust the Threshold, which corresponds to amplitude on the Y-Axis. It will move the 'auto-pick' location.

2. Go to ABS ZOOM tab (Figure 89): Here you see a zoomed window of the absolute (ABS) signal value. Verify that the 'auto-pick location' is at the zero crossing after the first significant wave above noise levels (not at the first arrival peak), use the Threshold slide bar to adjust its location. By changing the threshold value the 'auto-pick' location will change in steps and the velocity will be recalculated. 

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Note: The program must be running for changes to apply.

Figure 89. - ABS Zoom display with threshold slide bar and uncorrected auto-pick location.

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1. Pause the program.
2. Select MANUAL PICK tab (Figure 910).
3. Click on the crosshair tool on the far left side of the toolbox bar. Hover over the dotted yellow-green vertical pink line. When the icon changes, click and drag the pick line to the desired location and release. The Velocity –Manual box will be updated with the manually picked velocity. Both the 'auto-pick' and 'manual pick velocities' are saved simultaneously to the database upload.

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Figure 910. - Manual Pick display with yellow-green pink manual pick location.

C) Running a Standard as a QAQC Check

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1. Click the MUT Icon. Log in using database credentials.
2. 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 711).

Figure 711. - Main MUT screen

3. To manually upload files, check each file individually and clip upload. To automatically upload files, click on the Automatic Upload checkbox.

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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.

All improvements to the Quick Start Guides and User Guides are a communal effort, with honorable mention to the group of LOs, ALOs, and technicians who have helped.

Archived Versions

P-Wave Quick Start Guide - 27Sept2022

LMUG-P-WaveQuickStartGuide: An exported PDF version of this wiki page as of 2020-10-28.

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