Introduction

The P-wave velocity gantry measures the speed at which ultrasonic sound waves pass through materials that are placed between its transducers. 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). A laser measures the position of the top of the split-core section, and using this, along with the known distance to the transducers, calculates the position at which the velocity was measured (this is recorded as Offset in the LIMS Database). 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) using the PWC. 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.

Figure 1. Section half measurement directions.

Method Theory

Measurement of P-wave velocity requires an estimate of the travel time and an accurate measurement of the ultrasonic P-wave path length through the sample.
Velocity is defined as follows:
velocity = pathlength/traveltime, or
v = dS/dt.
Traveltime measurement is estimated by an algorithm for graphical first arrival pick. An ultrasonic pulser generates a high-impulse voltage, which is applied to the ultrasonic transmitter and thereby induces oscillation of the crystal element within the transducer-specific frequency band. A trigger pulse from the pulser is then applied to the oscilloscope to record the waveform from the receiving transducer.
By measuring the acoustic traveltime of the waveform through both specimen of the same material but variable thickness and instrumentation, linear regression through the dS/dt plot provides the instrumentation-specific time delay. Subtraction of the system delay time (+ liner material propagation time, if required) from the total traveltime gives the traveltime for the ultrasonic pulse through the sample.
Precise thickness of the sample, or path length, is derived from the readout of an Acuity AR700 laser displacement sensor. The laser offset correction is determined during the calibration process and requires that the system fully close the transducer caliper when the software is opened and activated. Therefore, do not place a core section underneath the transducers when the software is started.
The chisel (bayonet) transducers are fixed at 82.32 mm for the z-axis (downhole) and 31.70 mm for the y-axis (IODP axis designation). The x-axis caliper separation is derived from an Acuity AR700 laser.
Traveltimes for sample half sections are calculated as follows:
x-axis = total traveltime – x-system delay time – liner traveltime (section-halves only)
y-axis = total traveltime – y-system delay time
z-axis = total traveltime – z-system delay time
Liner traveltime is calculated as the liner thickness (typically 2.7 mm) divided by the published liner material velocity (cellulose butyrate = 2140 m/s).

The travel times for any measurement signal is based on either a user selected location on a graphical display of the first arrival wave (manual pick), or a software auto-pick feature, which attempts to determine the first arrival of the measurement signal.  The auto-pick feature will search for the first instance of a signal stronger than a user set threshold value (milli-amps).  Next it will take the absolute value of the signal and determine where the wave-form crosses the graph's x-axis the 2nd time.  It will then subtract an assumed 1/2 of wave length, and display the pick location on the same graphical display.  This should get the travel-time of the measurement signal.  Verification of the signal and pick location by the user is critical.

P-Wave Measurement Overview

A temperature-equilibrated split core section-half  in it's liner is placed on the core track. The user positions the section half under the sensor, places a small piece of glad wrap on top of the core, and triggers the measurement from the software control panel. The measurement is taken continuously, with the recorded result representing the average of several thousand determinations.  A barcode reader records all relevant sample information, which is used for the data upload into LIMS. A laser sensor measures the distance to the top of the section-half and determines the sampling interval from the known sensor offsets.  Discrete measurements are discussed in the Caliper Measurement section below.

Caliper Measurement

• The sample is placed between 2 flat, 1 inch diameter sensors that squeeze firmly onto the specimen to ensure good contact.  De-Ionized (DI) Water is introduced between the sample and sensors to aid in signal propagation.
• One sensor acts as a transducer and the other as a receiver to record velocity measurements at a rate of 0.5 MHz.
• To measure discrete samples, the sample is measured along each (x, y, and z-) axis between the caliper sensors.
• A series of polycarbonate standards of different thickness are measured to obtain a linear regression transit time vs. distance for calibration. Their industry-calibrated standard sonic velocity is 2.750 m/s.

Bayonet Measurement

• Two pairs of piezoelectric transducers set at 90° to each other are inserted into the unconsolidated or semisoft section-half materials until the sensors are buried in the material to be measured.
• One of each pair of sensors acts as transducer and the other as receiver to measure velocity in two directions simultaneously.
• Calibration is performed by inserting the probes into a container filled with distilled water of known temperature, and therefore known velocity.

Data Quality

Velocity data quality is affected by several variables:

• Quality of the acoustic coupling between the core material and the sensor transducers. Note: Use water to increase the quality of the contact.
• Quality of the coupling between both the transducer and the core liner and between the core liner and sample. Note: Use water to increase the quality of the contact.
• Consolidation of the sediments; noncohesive sediments containing microcracks or gas voids cannot be measured accurately.

Apparatus, Reagents, & Materials

Hardware

The velocity track system consists of the following components (Figure 2):

• Caliper transducers: X-axis velocity measurements
• Chisel-type transducers (bayonet transducers): Y and Z axis velocity measurements
• 3 Linear actuators: Each actuator controls the motion for one instrument 
• Laser Range Finder (AR1000 laser): Used to determine offset of measurements on section halves
• Displacement Laser (AR700): Used to determine distance between caliper transducers during measurements
• Two Signal Amplifers: Used to amplify the signal from the caliper transducers.  Adjustments on the gain dial are made when the signal is noisy.

Figure 2: Bayonets, caliper and displacement laser on the Gantry track (left), signal amplifer (center), and laser range finder (right).

Caliper Transducers: Panametrics-NDT Microscan Delay Line Transducers

Bayonet Transducers

Custom made.

Exlar Linear Actuator

Acuity 1000 Laser Distance Sensor

Acuity AR700-4 Laser Displacement Sensor

Standards

Various standards are available for the P-Wave Gantry system (Figure 3).  These include:

• Laboratory reagent water (distilled) (for the bayonet calibration)
• Aluminum block of known length and velocity; velocity = 6295 m/s (for caliper calibration)
• Acrylic half-cylinders of variable thicknesses; the assumed Acrylic Velocity as of June, 2019 is 2730 m/s.  

It is recommended that the standard used for calibration be similar in size to the sample being measured.  

 Figure 3. Velocity Standards.

Launching the IMS-Velocity application

The IMS-Velocity software can be launched from the Windows Start menu or from a desktop icon (Figure 34).  

Figure 4. Velocity Desktop Icon

At launch, the program begins the following initialization process:

• Tests all instrument communications
• Reloads configuration values
• Homes the Caliper and Bayonets  Do Not place samples on the track before launching the software.

CAUTION: When first opening the program, all 3 sensors will go through a communication initiation process where they will move down and up; the program will display a warning message first (Figure 5). However, make sure there are no samples or body parts underneath any of the sensors.

Figure 5. Track Initialization Warning

After successful initialization, the main IMS-Velocity window will appear (Figure 6).

Figure 6. Velocity IMS Main Window

The software home screen allows the user to modify a number of setup and acquisition parameters directly, as well as control the motion of the transducers.

The main window (Figure 67) includes:

1. Sample type and Measurement Axis selection: The user selects the type of sample, while simultaneously selecting the measurement axis via the pictured tilesMotion Control Buttons: These control the up-down motion of the caliper and bayonets.  The user may select to make slow or fast movements.
   
2. Graphical Display Tabs:  The RAW, RAW STACKED, and RAW ZOOMED tabs will display the measurement signal without mathematical manipulation.  The also display the auto-pick location.  The ABS and ABS ZOOM tabs display the absolute value and the uncorrected auto-pick location, which should be between the 1st and 2nd hump.  These displays are crucial for evaluating the signal quality and pick locations.Mini Graphs: VELOCITY graph displays the running average of the last 1,000 samples and the TORQUE graph display the torque applied by the actuators to the sample.  The Distance graph displays the AR700 distance readings.
3. Requested Stack and Threshold sliders:
   1. Requested Stack: The number of measurement signals the software will add together with the intent of increasing the signal to noise ratio. Each time it is adjusted a new set of signals will begin stacking.  100 stacks is a typical value.
   2. Threshold:  Voltage level (y-axis of the graphical display mV) that the stacked signal must attain for consideration in a auto-pick.  If the threshold is too low, signal noise may be selected as the first arrival.  If the threshold is too high, the first arrival may be missed and included with the signal noise.
4. Mini Graphs: VELOCITY graph displays the running average of the last 1,000 samples and the TORQUE graph display the torque applied by the actuators to the sample.  The Distance graph displays the AR700 distance readings.
5. Motion Control Buttons: These control the up-down motion of the caliper and bayonets.  The user may select to make slow or fast movements.
6. Pause Button: By Pause Button: By selecting the pause button, the user will be able to make manual picks and have the velocity of that pick displayed.
7. Save Data: The save button is activated when an automatic velocity pick is within the velocity filter range or when a manual pick is made.

Image Added

Figure 7: Main Velocity Window with annotated sections

A Quick Introduction to the IMS Program Structure

IMS is a modular program. Individual modules are as follows:

• INST plug-in: code for each of the instruments
• MOTION plug-in: code for the motion control system
• DAQ Engine: code that organizes INST and MOTION plug-ins into a track system

The Velocity system, specifically, is built with three INST modules (Caliper, Y-Bayonet, Z-bayonet), three MOTION modules (one for each instrument actuator) .

The IMS Main User Interface (IMS-UI) calls these modules, instructs them to initialize, and provides a user interface to their functionality.

Each module manages a configuration file that opens the IMS program at the same state it was when previously closed and provides utilities for the user to edit or modify the configuration data and calibration routines.

The three buttons on the left side of the IMS-UI window provide access to utilities/editors via dropdown menus as shown in Figure 78.

Figure 78. IMS Control Panel Drop Down Menus

Initial Instrument Setup

Velocity Configuration

Configuration values should be set during initial setup and configuration by the physical properties technician.  There should be no need to change these values unless the configuration files is corrupted.  This window allows the user to view and modify the physical configuration values for the Velocity system, as well as the liner correction values and the velocity filter settings.

Velocity Instrument General Setup

To open the Velocity instrument setup window (Figure 89), select Stations > Velocity Setup from the IMS panel menu (Figure 78).

1. Ensure the values in the window are set as shown in 
   1. Caliper and Bayonet Offsets: physical offset from the laser zero point to the center of the transducer pair for the three stations (caliper, bayonet Y, bayonet Z). This measurement will not change unless the station location is physically changed.
   2. Axis Separation: physical distance between the bayonet transducer pairs. This measurement should never change unless the bayonets holders are physically changed.  The X-Axis is not shown because its separation is determined during calibration and measurement by the AR700 laser
   3. Liner Correction: the liner delay valued as determined experimentally based on the liner thickness and velocity measurements on the liner material
   4. Velocity Disable "Save" Filter: when the filter is enabled, the save feature is inactive for any automatic velocity picks outside of the velocity range set.  
2. Click Ok to accept to save the changes and write them to the configuration file.  Click Cancel to rever to previous values.

Image Modified

Figure 89. Velocity Parameters Window

Instrument Calibration

The bayonet and caliper transducers must be calibrated and the system delay determined whenever a check standard is out of range, +/-2% of the expected velocity.

• The bayonet transducers are calibrated by back-calculating the system delay from the total traveltime, for the y- and z-axes, from the transducer separation value and theoretical velocity of distilled water at the temperature of the water bath.
• Calibration of the caliper requires the transducer and system delay to be calibrated concurrently. The transducer separation is measured with a displacement laser.

System delay is derived from the separation entered by the operator for the calibration standard and traveltime is derived from a traveltime pick algorithm. As the current transducers have pliable plastic pole faces the system delay is on the order of 25 µs, closing the calipers too hard produces unwanted variation. 
The calibration uses the derived velocity of the standard material to test for acceptance or rejection of the data.  Aluminum, the material used as the calibration standard for the caliper, has a published sound speed of 6295 m/s.

Caliper Calibration

To open the Caliper calibration window (Figure 910), select Stations > Caliper Calib. from the IMS panel menu (Figure 78).

Calibration requires correcting the displacement laser's offset and determining the system delay.  Calibration is completed with an aluminum block of the following approximate dimensions; 50.80 x 76.25 x 30.60mm .  (Figure 3).  

To calibrate the caliper:

1. Open the Caliper Calibration window
2. Place a drop of water on the lower transducer 
3. Place the aluminum standard on the lower transducer along an axis of known dimension.  Commonly the 50.80 mm axis is used as it is closest in thickness to a section-half.   
4. Verify the Aluminum width on the right side of the window matches the block width, i.e. 50.80 mm. 
5. Place a drop of water on top of the aluminum block.
6. Use the Close Slow or Close Fast buttons to close the caliper on the aluminum block.  Do not over close the transducers as a greater force will vary the physical distances of the caliper system.
7. Verify the software is picking the first arrival wave in the Raw Stacked graph tab. You can adjust the threshold scale bar to achieve the proper pick location (Figure 9). Observe the graph to verify the system is getting a clean signal.  If you are not getting a clean signal, follow the steps in the trouble shooting section of this guide.
   Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom).  This pick should be at the zero crossing after the first wave form (Figure 9).
8. Select Laser Offset Correction and verify the distance shown corresponds to the aluminum width.
9. Verify the aluminum velocity is properly set (6295m/s)
10. Select Determine System Delay
11. Verify the velocity shown on the screen is now 6295 m/s plus or minus 25 m/s.
12. If the displayed velocity is correct, select Accept changes.  To leave with out saving the calibration, select Cancel Changes.
13. As a check on your calibration, measure the velocity of the aluminum block and an acrylic standard to verify it is within an expected error margin, +/- 2.5%.  The assumed Acrylic Velocity as of June, 2019 is 2730 m/s.  It is recommended to use an acrylic standard of a similar thickness to what the user will be measuring, i.e. a core section or cube sample.  Ensure one of the discrete caliper sample types is selected for this measurement.
    
    

Figure 910. Caliper Calibration Windows.  Raw data graph tab (left) and the ABS zoom graph tab (right)

Bayonet Calibration 

Because the distance between the bayonets is fixed, only the system time delay needs to be calculated. This is achieved by measuring the velocity in water of known temperature, the difference between the known and measured value is due to system delay.

To open the Bayonet calibration window (Figure 1011), select Stations > Y-Bayonet Calib. or Z-Bayonet Calib. from the IMS panel menu (Figure 78).

To calibrate the bayonets:

1. Fill the bayonet calibration liner with DI water (Figure 1112).  The water level must be high enough that the black transducer pads on the bayonets can be placed below the water line without touching the liner itself.  The water should be at room temperature if possible.
2. Place the liner below the bayonets.
3. Open the bayonet calibration window for the selected axis

4. Verify the bayonet separation value.  If the value is incorrect, return to the Velocity Setup window (Figure 89) to edit the value.

5. Use a thermometer to measure the temperature of the water in the calibration liner
6. Enter the temperature value in the Temperature field next to the Water Velocity Calculator (lower left of the window).  The screen displays a plot of theoretical velocity of water vs. temperature. 
7. Use the Insert slow or Insert fast buttons to lower the bayonets into the water until the black transducer pads are submersed.  Use care when lowering the Y-bayonet to ensure you do not contact the core liner.
8. Verify the software is picking the first arrival wave in the Raw Stacked graph tab. You can adjust the threshold scale bar to achieve the proper pick location (Figure 1011) as long as the signal is not too noisy.  Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom) (Figure 1011).  This pick should be at the zero crossing after the first wave form (Figure 1011).  An algorithm calculates the temperature-corrected velocity of the water bath and displays the result in the Corrected Velocity field. 
9. Select Determine System Delay. The computer calculates the system delay based on the separation distance and theoretical velocity of water. 
10. Compare the corrected velocity to the calculated H20 velocity value.  If the values are not within range, redo the calibration.
11. Select Accept Changes to save the calibration or select Cancel Changes to leave without saving the calibration.
12. As a check on your calibration, measure the velocity of the water to verify it is within an expected error margin, +/- 2.5%.  Ensure the proper sample type is selected when verifying the calibration.

Figure 1011. Y-bayonet and Z-bayonet Calibration windows.  Y-bayonet raw graph tab (left), Z-bayonet raw graph tab (center), Y-bayonet ABS Zoom graph tab (right).

Figure 1112. Bayonet Water Standard

Sample Preparation

• Section-half core samples
• Discrete samples

Sample Prep Overview

• Before placing the working half in the core tray, make sure the surface is clean (lightly scrape away any material smeared across the cut surface during core splitting).
• Place the core section in the tray and make sure it is as flat as possible.
• Place a small piece of Glad Wrap over the desired Caliper measurement location.  This will keep the transducers clean and allow the user to add a small amount of water between the core and transducers.

Instrument Preparation

• Clean transducers of any residue with water and paper towels.
• Before initializing the P-wave software, ensure the caliper transducers and laser beam are not blocked. Note: This step is crucial.

Sample Analysis

Measuring Section-Half Samples

Caliper Measurements

The caliper can be used to measure section half and discrete cube samples. Before Before measuring samples, be sure the samples are properly prepared and the system is calibrated.

1. Place section half below the caliper or bayonets.  Take care to not drag the core against the bayonets while placing the core on the track.
2. Select the proper instrument and measurement axis button
3. Lower the bayonets into the section half until the black transducers are below the sediment surface.  For caliper measurements, close the transducer onto the core until contact is made.  Do not over squeeze the section half.
4. Verify the automatic velocity pick in the Raw Stacked graph tab. You can adjust the threshold scale bar to achieve the proper pick location as long as the signal is not too noisy.  Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom). This pick should be at the zero crossing after the first wave form.
5. Select Save Data
6. Verify the measurement offset.  
   1. If the offset is incorrect, select cancel and select Save Data again.  The laser range finder sometimes struggles to return a proper offset if the end cap is not opaque or if the core is not flat on track.  Try adding a post it note or opaque end cap to the section half if the laser returns the wrong offset.
7. Once the measurement offset is verified, scan the section half barcode label to populate the fields of the Scan Sample Label dialog box.
8. Select Save.

If contact between the transducers and sediment is poor, add distilled water around the transducers to improve contact with sediment.

Measuring Discrete Samples

Discrete samples measured on the Cailper station are hard material that has been cut from the core as cubes, minicores, or slabs. Because the material can be measured in various orientations, the user must select the measurement axis (see Appendix A).
Traveltime is calculated as total traveltime minus x-system delay time. Discrete sample measurements are not corrected for the core liner nor is an offset recorded in the LIMS. The transducer separation is measured with an LDVT as it is for the sample half measurement. For discrete samples the axis of measurement is selected for each measurement.
Retaining the correct "up" direction is critical for axis determination and P-mag orientation; make sure the sample has the "up" direction marked on it (see Figure Appendix A).
Before measuring samples, be sure the samples are properly prepared and the system is calibrated.

Section halves measured on the Caliper station are working half sections placed on the track with the blue end cap (top of section) toward the AR1000 laser.  The laser measures the distance to the top of the section and the software calculates the offset to the measurement based on the known section length.  

Discrete samples measured on the Cailper station are hard material that has been cut from the core as cubes, minicores, or slabs. Because the material can be measured in various orientations, the user must select the measurement axis.
Traveltime is calculated as total traveltime minus x-system delay time. Discrete sample measurements are not corrected for the core liner.  The offset recorded in LIMS is the top offset of the discrete sample.  The AR1000 laser is not used for discrete measurements. The transducer separation is measured with the displacement laser, as it is for the sample half measurement. For discrete samples the axis of measurement is selected for each measurement.
Retaining the correct "up" direction is critical for axis determination and P-mag orientation; make sure the sample has the "up" direction marked on it.
Before measuring samples, be sure the samples are properly prepared and the system is calibrated.

Section Half Measurement Procedure:

1. Place section half below the caliper.  Take care to not drag the core against the bayonets while placing the core on the track.
2. Place a drop of distilled water below the section on the transducer and on top of a piece of Glad Wrap on top of the section to improve contact between the caliper and section.
3. Select the proper instrument and measurement axis button (Caliper SHLF X-axis)
4. Close the transducer onto the core until contact is made.  Do not over close the caliper on the section half.  
5. Verify the automatic velocity pick in the Raw Stacked graph tab (Figure 10). You can adjust the threshold scale bar to achieve the proper pick location as long as the signal is not too noisy.  Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom). This pick should be at the zero crossing after the first wave form.
6. Select Save Data.  A sample information window will appear (Figure 13).
7. Verify the measurement offset.  
   1. If the offset is incorrect, select cancel.  The laser range finder sometimes struggles to return a proper offset if the end cap is not opaque or if the core is not flat on track.  Try adding a post it note or opaque end cap to the section half if the laser returns the wrong offset.  Select Save Data again.
8. Once the measurement offset is verified, scan the section half barcode label to populate the fields of the sample information box.
9. Select Save Data.

This procedure can also be used for whole rounds, but this is rarely used.
Image Added

Figure 13. Section Half Caliper Measurements Sample Information Window

Discrete Sample Measurement Procedure:

For each axis to be measured:

1. Place a small drop Place a small drop of water on the lower caliper transducer
2. Place the discrete sample on the caliper and add a drop of water to the top of the sample
3. Select the proper instrument and measurement axis button (Caliper X-Axis, Caliper Y-Axis, Caliper Z-Axis).
4. Lower the upper caliper transducer onto the specimen.  Do not apply unnecessary force on the specimen as it may fracture.
5. Verify the automatic velocity pick in the Raw Stacked graph tab (Figure 10). You can adjust the threshold scale bar to achieve the proper pick location as long as the signal is not too noisy.  Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom). This pick should be at the zero crossing after the first wave form.
6. Select Save Data.  The sample information window will open (Figure 14).  Note that the measurement offset will not be populated.  The laser range finder is not used for discrete measurements.
7. Scan the discrete sample barcode Scan the section half barcode label to populate the fields of the Scan Sample Label dialog sample information box.
8. Select Save Data.

If the material to be measured is a whole piece removed from the liner (rarely used), select Piece w/o Liner mode in Step 4 and complete the offset (position of the piece in the liner before it was removed) in the Additional Piece Information dialog box (Figure 30).

If the orientation of the piece is unknown, check the Orientation Unknown box; otherwise the measurement is assigned to the X-direction.

11. Repeat the measurement process for each axis to be measured.

Accepting Results and Manual Pick

Once the velocity data have been acquired, the results are shown on the Display Results screen (Figure 32).

1. Select the Manual Pick Arrival Time button to open the Manual Pick screen (Figure 33.A), showing the waveform. To help select the first arrival, the plot can be zoomed in using the graph palette zoom function or by entering Zoom Range Minimum and Zoom Range Maximum (27. to 40.) below the waveform plot on the Manual Pick screen. Select the Cursor Movement Tool on the graph palette, then use the mouse to drag the red cursor line to the first arrival, this should be the slope of the first positive peak at zero (Figure 33.B).
2. Click Continue to accept the manual pick and save it to the data file or Cancel to discard the manual pick results.

Image Removed
Figure 33.A Manual Pick Screen. 

Data Handling

From the Display Results screen one of 4 data handling choices can be selected:

Caliper Piece X-Axis in Step 3. The measurement offset field in the sample information window is selectable.  Scan a section half label and enter the offset of your measurement from TOP OF CORE?  Currently Piece Measurements offset do not work

Image Added

Figure 14.  Discrete Caliper Measurements Sample Information Window

Bayonet Measurements

Before measuring samples, be sure the samples are properly prepared and the system is calibrated.

1. Place section half below the bayonets.  Take care to not drag the core against the bayonets while placing the core on the track.
2. Select the proper instrument and measurement axis button (Y or Z bayonet)
3. Lower the selected bayonets into the section half until the black transducers are below the sediment surface. 
4. Verify the automatic velocity pick in the Raw Stacked graph tab (Figure 11). You can adjust the threshold scale bar to achieve the proper pick location as long as the signal is not too noisy.  Also, verify the auto-pick location in the Absolute Value tab (ABS or ABS Zoom). This pick should be at the zero crossing after the first wave form.
5. Select Save Data.  A sample information window will appear (Figure 13).
6. Verify the measurement offset.  
   1. If the offset is incorrect, select cancel and select Save Data again.  The laser range finder sometimes struggles to return a proper offset if the end cap is not opaque or if the core is not flat on track.  Try adding a post it note or opaque end cap to the section half if the laser returns the wrong offset.
7. Once the measurement offset is verified, scan the section half barcode label to populate the fields of the sample information box.
8. Select Save Data

Manual Pick

In some cases, a user may wish to make a manual pick.  This usually occurs because the automatic pick is unsuccessful, often due to a noisy signal.  Often, the Save Data option will not be available for a bad automatic velocity pick, because the values are outside of the velocity filter range. Figure 15 shows an example of a situation in which adjusting the threshold value could not overcome a large peak at the start of the measurement. Using the manual pick, the user is able to override the computers pick.  Both the automatic velocity pick and manual pick are recorded in LIMS.  This option is available for all measurements on the Velocity-Gantry track.

To make a manual pick:

1. Place sample in the selected instrument
2. Once a signal is visible on the graphical display, select the Pause button in the lower left corner of the main window (Figure 7).
3. The manual pick tab will be displayed on the screen (Figure 15).
4. Slide the red line along the x-axis to the desired pick location.  The line should be placed at the first arrival. To help select the first arrival, the plot can be zoomed in using the graph palette zoom function in the lower left corner of the graphical display. What is the proper method of selecting?  First positive peak?
5. Verify the Velocity-manual value is reasonable for the material measured.
6. Select Save Data.  The sample information window will open.
7. Scan the sample barcode label and save the data to the LIMS database.

To exit the manual pick and return to the automatic velocity pick, press the Play button.

Image Added

Figure 15. Manual Pick Graphical Display

Image Added

Utilities

LIMS Integration

Sample/Analysis Attributes and Components

Data Upload Procedure

Data is automatically saved to the C:/Data/In folder on the computer.  The MegaUploadaTron application locates these files and uploads them to LIMS.  Once the upload is completed the data is moved to C:/Data/Archive.

Health, Safety, & Environment

Safety

• Keep extraneous items and body parts away from the moving parts.
• The track system has a well-marked yellow and red emergency stop button (Figure 34) to halt the system if needed.
• Do not look directly into the laser light source (class 2 laser product).
• Do not direct the laser beam at other people.
• Do not attempt to work on the system while a measurement is in progress.
• Do not lean over or on the track.
• Do not stack anything on the track.
• This analytical system does not require personal protective equipment.

Figure 34. Emergency Stop Button.

Maintenance & Troubleshooting

Common Issues

The following are common problems encountered when using the P-wave Velocity Gantry and their possible causes and solutions. For information about the laser Measurement and Operation software, see the Vp GIESA Gantry Laser Operation manual.

Figure 35. Actuator Utilities.

Scheduled Maintenance

After Every Sample

Clean contact sensors with tissue, cloth, or paper towel and water.

Daily

Clean dust from the laser sensor lens using compressed air or delicate tissue wipes. Do not use organic cleaning solvents on the sensor lens.

Weekly

Check set screws on piezoelectric transducers to make sure they are firmly held in position when embedding in sample.

Annually

Coat (not pack) the following parts with grease:

• Angular contact thrust bearings
• Roller screw cylinder
• Roller screw assembly in the actuators

Examine the cable management system for abraded cables or other indications of wear.

Vendor Contact/Consumable Parts

Panametrics transducer

Olympus (www.olympusndt.com)

• Transducer: NDT M2008

Transducer couplant

• Couplant A
• Couplant B

Laser displacement sensor (AR1000)

Acuity Laser Measurement
www.acuitylaser.com
702-616-6070

Barcode reader (MS-4)

Microscan
www.microscan.com
helpdesk@microscan.com
800-251-7711

Actuator (TLM 20)

Tritex
www.exlar.com

Related Documentation and Links

• Vp GIESA Gantry Laser Operation manual
• Olympus Panametrics-NDT Ultrasonic Transducers
• Acuity Laser Measurement AccuRange AR1000™ Laser Distance Sensor User Manual
• Acuity Laser Measurement AR1000 Laser Distance Sensor: Quick Start Guide
• Acuity Laser Measurement AR1000 Laser Distance Sensor Data Sheet
• Exlar Tritex Linear & Rotary Actuator Installation, Operation, and Service Manual
• Exlar Tritex Technical Notification 4/12/07

Credits

This document originated from Word document P-Wave Velocity Gantry: User Guide (see Archived Versions below for a file copy) that was written by T. Cobine (2009-01-17), reviewed by H. Barnes and T. Gorgas, and approved by D. J. Houpt. Credits for subsequent changes to this document are given in the page history.

Archived versions

• P-Wave Velocity Gantry: User Guide: Word file written by T. Cobine (2009-01-17), reviewed by H. Barnes and T. Gorgas, and approved by D. J. Houpt