Table of contents


Pile Echo Tester

User Manual

About this Manual

This is the user manual for the Pile Echo Tester (PET). You can connect your PET hardware to a computer running one of the following operating systems: MS Windows XP, Windows 2000, Windows 7, 8, or 10. The Bluetooth PET hardware can also be used with mobile devices running the Android operating system. All data files are stored in an identical and fully interchangeable format in both the Windows and Android versions of the PET software.

Note: This user manual is intended for both the USB and the Bluetooth PET hardware. The USB and Bluetooth symbols in this manual indicate which feature is relevant for which model.

Structure of this Manual

The first part of this manual is the Getting Started / Tutorial section that will let you begin using your equipment as soon as possible.

We have included a detailed explanation of every function in the Reference section of this manual. You can directly access this section by clicking on the links provided in the text.

We have grouped features together in the Features by task section, to help you perform tasks more easily.

Additional information such as the Theoretical Background section, is at the end of this manual in the Appendix.


Tap/Tapping - Use the hammer to hit the pile and create the sonic

Impact - The raw-data recording captured after every hammer tap on the pile

Reflectogram - The plotted trace of each impact - on screen, or on paper, after processing is complete

Wave speed - This is the wave speed measured by our equipment. In the past we used the term 'Velocity' instead of wave speed.

Know your PET

USB PET connected to a Tablet PC (Not included)

Bluetooth-PET with an Android device

Hardware Block Diagram

Getting Started


Software and hardware setup are independent of each other, and either can be installed first.

Software Setup

  1. To install the software, use one of the following options:
  • Either insert the USB flash-drive or CD provided, and click on 'PET'. You can also look for the PETSetup.exe installer and double-click on that. The setup will begin automatically.
  • Or download the latest PET software from the user community website:
  • To obtain your password please email our support desk using this email address:
  • Or download the application (only for Bluetooth PET version) from: PET App, or search for the Piletest application on Google Play.
  1. For Windows based systems:
  1. Follow the default setup to install PET (this typically takes less than 1 minute).
  2. In case the setup does not start automatically, locate and run the PETSetup.exe file on the CD / USB Flash drive provided.
  3. The PET software is installed in the following location: [Start]-[Programs]-[Pile Testing]-[PET]

Hardware Setup


  1. Plug the USB connector of the PET device into one of the USB ports of your computer (PC)
    The ...Found new hardware... balloon, and the wizard with the same name should open automatically
  2. Follow the wizard's instructions
  3. Connect the USB flash-drive or insert the CD provided with the PET software and press [next]
  4. The Wizard will start copying the driver files from the CD or USB drive
  5. Windows XP system may display a security warning - you can safely press [Continue Anyway] PET's driver is fully tested and will not impair the stability of your system!
  6. After the files have been copied, close the wizard by clicking [Finish]


There is no need to set up any hardware drivers for the Bluetooth version of PET

See Connecting the Bluetooth PET to Windows

Contacting Piletest

If you encounter problems setting up your PET, or testing, or interpreting the results please contact us without hesitation

See: contacting Piletest

Instructions Specific to the Bluetooth PET System


The unit is operated by two alkaline AAA batteries. The combined minimal battery voltage is 2.1V - Rechargeable batteries usually give lower voltage and cannot be used.

Ensure that you insert the batteries correctly (there is a '+' sign near the battery cover opening).

Use batteries only from a reputable manufacturer such as Duracell, GP, Energizer, etc.

Please note that there is a small length difference between AAA batteries of different manufacturers. The Bluetooth PET sensor does not have a spring in the battery compartment (to prevent mechanical noise interfering with the test) so slightly smaller batteries do not reach the contact plate. Please make sure the battery '+' contact fits tightly in the battery holder - otherwise you may need to use batteries from another manufacturer.

The batteries should typically last for 200-300 piles. This may vary depending on factors such as the number of blows per pile, the length of the piles, the idle time between testing, and time in storage.

You can keep working with flat batteries until the unit is no longer responsive. The data sampling accuracy is not affected by the battery level.

Never replace batteries in the rain or under conditions where water can enter the inside of the unit.

To protect our environment, please deposit used batteries responsibly in battery recycling bins.

The batteries should be removed when you are moving the system, especially when flying, to prevent unintentional activation of the system.

General Operation

The unit has a built-in impact switch. To start the system, simply tap the unit lightly on the top of the pile. The system will enter "discoverable mode" and will wait for a connection from the Bluetooth-enabled device. (See LED Indications)

If the case is firmly closed and the O-Ring is intact, then the unit is fully waterproof. If the O-ring is damaged you need to replace it (you can obtain this free of charge from Piletest).

LED Indicators

LED Blinking

Possible Reason

No blinking

The system is Off (Tap to switch it On)

The batteries are dead

The system is connected and logging data. In this case every movement will generate a short blink.

10 blinks in succession


The batteries have been replaced

The cover was opened and closed

2 fast blinks every 1.5 sec (heartbeat)


Discoverable mode
The unit is waiting for a connection by a PC

If no connection is made within 2 minutes the system shuts down to conserve battery life

1 blink every 2 seconds


The system is connected to your computer, but is not logging data

1 short blink


Impact data was sent to the computer

A command was received from the computer

LED light fades down and up again


The battery power is low

50 very frequent blinks


Error, contact Piletest

Connecting the Bluetooth PET to a Windows Computer

Note: PET supports Bluetooth Ver. 1.0 or higher

To connect your Bluetooth-PET sensor to your Windows-based computer:

(You only need to run this setup procedure only one time for every computer)

  1. Make sure the Bluetooth hardware is enabled in your computer
  2. Make sure that there you have installed batteries in your Bluetooth PET sensor.
  3. Bring the sensor to "discoverable" mode. See General operation
  4. Right-click the Bluetooth icon on the taskbar and select [Add a bluetooth device]
  5. Windows will locate your Bluetooth sensor and will display its' serial number
  6. Click [Pair] and enter the following passcode: 1234
  7. Windows will connect to your sensor. The status of the connector will now appear as: [Connected]
    Click on "More Bluetooth options"
  8. Find the row listing the serial number of your sensor, and Direction 'Outgoing' as shown in the screenshot here.
    Note the port number (COM 85 in this example).
  9. Start the PET software, select [Tools]-[Data source], select Bluetooth and click [OK]
  10.  Enter the Port number and click OK
  11. Your Bluetooth device is now connected.


Take the Built-In Tutorial

The built-In tutorial will teach you some useful basic testing scenario features.

You do not need to connect the PET hardware to use the tutorial because it uses a simulated data source.

Either start PET software in Tutorial mode ([Start]-[Programs]-[Pile testing]-[PET Tutorial]) or select Tutorial from the [Help] menu

The tutorial will guide you through a simple, basic testing workflow, and serves as a brief introduction to the PET software.

Testing a Pile

  1. Start PET
  2. [Start]-[Programs]-[Pile Testing]-[PET]

  1. If you want to use Imperial (US or UK) units (Feet)
  • Select [Tools]->[Options]
  • Switch to the [Misc] tab
  • Select ...English...
  • [Close]

  1. Select [File]->[New Project] and or click to enter the name of the project

  1. Locate the first pile in the site plan. Check that the pile head is clean.
  2. Select [Pile]-[Add] or click the [+] button 
  3. Enter the name of the pile
  4. Enter the planned length of the pile by dragging the top of the red triangle marker.

You can change this length later, however the length determines the sample size, and initial graph scales, so it should be as close to the actual expected length as possible.

  1. Change the scale by dragging the scale axis labels right or left. The scale should be large enough to contain all the expected length with a few meters extra length spare
  2. For now, leave the wave speed at the default 4000m/s. You can still modify it later

  1. Connect / Start the PET Sensor,
  2. Apply a small amount of putty to the bottom of the sensor.
  3. Press the PET sensor against a clean spot on the top of the pile with a force of ~1kg (~2 pounds)
  4. Click [Start] (See Troubleshooting)

  1. Start tapping the pile. Hit the pile sharply but lightly (equivalent to dropping a hammer from a height of 10-20 cm) and frequently (~2 times per sec)

    You can view a tutorial video of these test steps
  2. It will take some practice to get a good, clean hammer tap. If you were unable to collect any good impacts, Press [Stop],  [Reset] and [start] again.

  1. Start collecting data: You will need at least 10 very similar impacts, and up to 40 or 50 impacts in total. You will have the opportunity to sort them later in the office. We recommend that you spend another minute at the pile collecting some redundant data than to have to return again to the site.
    Experienced users can sometimes collect just 3 similar impacts in very easy-to-test piles - but this is the absolute minimum.
  2. The average impact is displayed as the reflectogram (big graph) in the reflectogram window, the individual impacts are on the right.


  1. Select [Stop] to stop logging. You can continue logging and add impacts at any time later on, even after saving the pile, or on another day.
  2. Optionally modify the presentation parameters on the impact tab by dragging the black bars - more details on Pile window
  3. You may tentatively delete some irregular traces by clicking on the [X] icon next to them. The effect on the average is shown immediately.
    Deleted impacts are stored in the pile's "recycle bin" and saved with it
  4. Click on the recycle bin icon to undelete the last deleted impact.
  5. As part of the characterization of the pile you may use the Data tab and Info tab which are described in detail in the Pile window section.
  6. Tap [Save] to save the pile
  7. You may now click anywhere on the pile row in the current project to re-open the pile., or click on to test more piles
  8. You may also scroll between the piles using the left/right arrows beside the SAVE button 
  9. Transfer the data to the computer for reporting and additional analysis

See also: Options 

Reflectogram Interpretation

IMPORTANT NOTICE: This chapter cannot, and is not intended to waive the need for professional interpretation by a qualified engineer. Ltd. does not encourage interpretation by unqualified personnel. The guidelines below should therefore be regarded as informational background and not as a substitute for formal interpretation training.

Signal Handling

To turn the raw data into an acceptable reflectogram, the PET software performs several operations. Some of these are performed automatically (marked ...Auto...), while others are done interactively by the operator (marked ...User...):

User defined presentation parameters:

  1. Filtering: To eliminate high-frequency noise and obtain a smooth curve the program uses a numerical low-pass filter (User).
  2. Amplification: Because of friction damping, the stress wave is weakened as it progresses along the pile. To obtain a legible reflectogram, it has to be compensated for damping, usually exponentially. In a well-balanced reflectogram, the impact from the top and the reflection from the toe should have approximately the same amplitude (User).
  3. Sharpening: This function emphasizes significant features of the reflectogram and down tones smaller ones. Do not overuse this function as it might hide data that you want to show. Use the minimal possible value.
  4. End-of-Line: Changing this mark, affects the maximal amplification point. It should be positioned just beyond the measured pile length (toe)

Automated presentation parameters:

  1. Integration: The PET sensor contains an accelerometer, but the graphical output presents particle speed. For this reason all signals must be converted from acceleration to speed (Auto).
  2. Shift-Rotate: The curve is rotated and shifted towards the horizontal axis. This prepares the reflectogram for the next step (Auto).
  3. Normalization: No two impacts are equal in intensity, and for this reason the resulting particle velocities are also different. In order to help you interpret the results, the vertical scale is adjusted so that the maxima and minima of the reflectogram occupy all the available vertical space (Auto).
  4. Averaging: A typical reflectogram will include a consistent component (signal) and a random component (noise). As a result, no two impacts will yield the same reflectogram. To improve the Signal/Noise ratio, the PET software automatically averages successive impacts as they arrive (Auto).

See also: Appendix 2 - Beginner's guide to PET Analysis

After completing these steps we hope you now have a neat reflectogram, and are interested to know what it can teach us about the pile. In fact, this is the inverse problem of taking a given pile shape and drawing the characteristics and the reflectogram. Like many inverse problems, it has no unique solution so that to get a reasonable approximation we have to make several assumptions. The first and most important assumption is that we are indeed testing a pile with an essentially cylindrical or prismatic shape.  To that we have to add additional information: The piling method, the soil profile and the supervisors' field notes.

Actual testing with the PET can be learned fairly quickly by qualified personnel. Interpretation, on the other hand, should be left to experienced geotechnical engineers with thorough knowledge of wave propagation theory, soil mechanics and piling technology. Of course, experts may make a few learned mistakes from time to time, but the ignorant make a lot of mistakes all the time. Hence, expert interpretation is the key to successful sonic testing.

Typical Pile Issues

The first step in analyzing the reflectogram is done on site, immediately following each test. This is done by comparing the graph to a mental picture of various pile shapes and their respective reflectograms. Some typical cases are presented in Table 1.

Note: Piles are drawn horizontally for ease of presentation.

Table 1: Typical reflectograms




Straight pile, free end, length as expected

Straight pile, fixed end,  length as expected

Straight pile, free end, shorter than expected

Increased impedance

Decreased impedance

Locally increased impedance

Locally decreased impedance

Multiple reflections from mid-length discontinuity - toe reflection indiscernible

Irregular profile - irregular reflectogram

If our reflectogram falls into one of these categories (except for the last one, of course), it means that we can explain the significance of what we have in hand. If the opposite is true, we have to try another spot on the pile (this often helps). If all our attempts fail, either the pile top was not sufficiently prepared for testing, or the pile profile is just not amenable to sonic testing.


Since the sonic method is based on the use of stress-waves, it can identify only those pile attributes which influence wave propagation. The following items may in many cases be detected:

  1. Pile length.
  2. Inclusions of foreign material with different acoustic properties.
  3. Cracking perpendicular to the axis.
  4. Joints and staged concreting.
  5. Changes in cross section.
  6. Distinct changes in soil layers.


All physical measurements, including the sonic method, have limitations. For instance, the sonic test normally does not detect the following items:

  1. The toe reflection when the pile's L/D ratio roughly exceeds 20 (In hard soils) to 60 (In very soft soils).
  2. Gradual changes in cross-section.
  3. Minor inclusions and changes in cross-section smaller than ±25% .
  4. Impedance changes of small axial dimension.
  5. Variations in length smaller than ±10%.
  6. Features located below a crack or a major (1:2) change in impedance.
  7. Debris at the toe.
  8. Deviations from the straight line and from the vertical.
  9. Load-carrying capacity.

A schematic summary of the above list appears in Table 2.

Table 2: Limitations

High L/D ratio and/or high skin friction
- no toe reflection

Progressive changes in cross-section

Minor inclusions

Deviations from the straight line

Deviations from the vertical

Producing a Report

The report is a RTF (Rich Text Format) file which is readable by all modern word processors.

To produce a report:

  1. Open your project,
  2. Modify all piles to the way you would like them to appear in the project by changing parameters, adding notes, etc.
  3. You may bulk-edit some parameters using [Pile]-[Modify all]
    This is especially useful for getting the desired number of piles per page by changing the [Row height] to a typical 200% value
  4. Edit the project's title and subtitle
  5. Select [File]-[Page setup] to change the page margins
  6. Select [Tools]-[Options]-[Logo] to select your logo.
  7. Select [File]-[Report]
  8. Modify the report parameters and press [OK]
  9. It is better to change the report parameters at the source (in PET) and not in the generated file. If changes are needed, close the file, make the changes to the piles in PET and create another report.
  10. The report is a document, and may be printed, emailed, faxed, converted to PDF or DOC formats, saved to other locations, merged with your final report, etc.

See Customizing PET Reports


This section explains each function available in the PET software in detail.

Project Window

  • The project window displays all the information related to the project folder.
  • The project title and subtitle appear in the final report, and in the ...Open project... dialog.
  • The piles table displays the table as close as possible to the way it will be printed.
  • The table is highly customizable: See Customizing PET reports.
  • Click on any pile row to analyze the pile, edit the reflectogram, or to add tests the pile.

Top Main menu

File menu

[File]-[New Project]

Opens the ...create a new project... dialog.

[File]-[Open project]

Opens the ...Open a project... dialog.

[File]-[Browse for a project]

Opens a standard windows dialog. Let's you open projects that are not in the standard folder, including network drives and CDs.

[File]-[Open project folder]

Opens the Windows folder where all the project files are stored. Useful for copying/archiving the whole project

[File]-[Project Summary]

Shows the current project summary:

  • The project title
  • The number of sub-sites
  • Total number of piles
  • Total number of tested piles
  • A summary for each sub-site: Name, number of piles and number of tested piles

Opens the Sub-Sites dialog, for renaming, deleting, and merging sub-sites

[File]-[Open project folder ]

Opens Windows Explorer on the project folder

[File]-[Pack project for mail (ZIP)]

Use this option to zip (compress) the whole project. The zipped project file may be sent to Piletest experts and support as part of our SOS (Second Opinion Service), complimentary service for PET systems under warranty.

  1. Select if you must include the photos in the project folder (this will make the ZIP much larger)
  2. Add free text as needed. We have created basic information to help you create an informative SOS request.
    Click [PACK] to create the ZIP file and open the project folder.
    Send this ZIP to for consulting,

Important Note: Piletest provides this service to support new users and for unusual cases, and relies on the completeness of the information we receive from you. Therefore ensure that you send as detailed information as possible that explains the issues you are encountering when asking for the SOS service, and also include as much site data as possible.


PET does not print directly to the printer; instead, it generates an RTF (Rich Text Format) file and opens your word processor. Most word processors (including MS Word) recognize this file format.

This approach gives you the option to:

  • Add final customizations to the report, change fonts, colors, add a preface, etc.
  • Preview the report using the strong preview capabilities of the word processor
  • Save the report together with the logged data
  • Email the report, or Fax it directly from the computer

You have the following options which affect the visibility of the report.

See also Appendix # - Customizing PET reports


All: Print report for all sub-sites.

Current: Print report for the current sub-site only.


New page for each sub-site: When this option is checked, PET will add a page-break after each sub-site

One page per pile: This changes the report table format, each pile is printed in one page, the reflectogram column will be printed as a separate table cell using the full width of the paper.

A photo, if available, will be added below the table.

Skip non-tested piles: If unchecked, the report will include even piles which were added to the project, but not tested.

Print planned length mark: Adds the red triangle to the report.

Print all impacts: Prints all the impact reflectograms, stacked.

Row Height

As seen on screen: The row height of each pile will match the height on screen.

Override with: Overwrites per-pile row height, and instead prints all piles using the same row height.


All: Print report for all piles.

Monthly: Print report for all piles tested during the current month.

Daily: Print report for piles tested today.

Last opened:  Prints just the most recently opened pile.

Word97 format (Deprecated)

For backwards compatibility - When checked, the generated file will be readable by Word97, but not by later versions.

See also:

Sub-Sites  Modify-All  Customizing PET reports

[File]-[Printer setup]

Opens the printer setup dialog (depends on your printer hardware). Use this to select paper size and orientation, as well as other printer specific options (such as quality, color, etc.).

[File]-[Page Setup]

Opens the page setup dialog, allows setting paper margins.


Closes PET.

Note that there is no need for a ...Save... option. Projects and files are always saved to disk.


A quick way to open one of the most-recently-used projects.

Pile menu


Opens the ...New pile... dialog. Also available with the direct button

[Pile]-[Add Multiple Piles]

Opens a dialog with which you can add a series of pile numbers with desired prefix, suffix, length and wave speed.


Removes the currently selected pile from the project. If the file contains data, a confirmation message box appears.

Removed pile files are moved into the Windows recycle bin. To restore a removed pile into the project, locate it using Windows Explorer, right-click it and select [Restore]. You will than need to close and re-open the project to make PET software register the added file.


Also available with the direct button

Opens the pile-sort dialog, which allows you to define the sort priority.

  • Sub-Site
  • Month/Day/None
  • Pile's name

Opens a dialog where you can do bulk-editing of pile parameters.

Using this dialog you can bulk-edit all piles in the current sub-site or project.

Tip: "Modify-All" is one of the many Labor saving features in the PET software.

There are seven fields that can be used for bulk-editing. You can adjust these fields by dragging the black bar to the desired value.

Note: if you leave a field unchecked - no changes will be made

Drag the black bar to set the value of the desired parameter

Row Height

Use this option to control the height of the printed rows in the report.

To print 10 piles per page, set the row height to 200%. This number may change according to your paper size, margins and printing preferences.

Length Scale

Enter the graph scale (X-axis value where the graph ends). Your report will look better, and it is easier to compare reflectograms of different piles if all are at the same scale.

Wave Speed

Wave speed of all piles cast of the same age is likely to be identical.


Change the amplification to compensate for the soil friction until the toe reflection appears the same size as the hammer impact.


Choose a filtering value, to eliminate high-frequency noise and obtain a smooth curve. The program uses a numerical low-pass filter. Here it is useful if there is a common noise which is associated with the site location.


Use sharpening to enhance some features (do not overuse it).

Planned Length

Enter the piles planned length. This is useful if this piece of information only becomes available AFTER the piles have been tested speed

Apply To

Select whether to limit the scope of changes to the current sub-site, or to the whole project.



Signal matching is an advanced analysis technique that helps you find a synthetic pile profile shape that would, theoretically and simplistically, produce a reflectogram that matches the recorded one with good proximity. The assumption that two profiles producing similar reflectograms are also similar isn't always correct. However, this method helps by providing secondary advice.

You may change the friction/impedance profiles manually to maximize the ...match quality....

  • Move a point by dragging it
  • Add a point by clicking between two existing points
  • Delete a point by right-clicking on it

To match automatically - Choose the Match Range and press [Match].

  • You may set a limit to the number of points that make up the profile
  • You may stop at any stage to change the friction profile and/or the impedance profile and then resume the matching process until a good fit is obtained.
  • [Match Quality %] is a numeric indication of the similarity between the measured and the calculated reflectograms.


Since this is an inverse problem, it has no unique solution. The impedance profile obtained is just one solution. It must be analyzed by an experienced engineer based on the soil profile and construction method before it is included in the report.

[Pile]-[Show Pile Counter]

Shows/Hides a simple counter that gets incremented on each pile tested. Double-click the counter to reset it.

This can be used when there is a request to test just a certain number of piles, or as a general way to track your progress.

Tools Menu


Opens the Options dialog, where you can customize the report columns and fonts, screen keyboard, logo, unit code and logger ID.

Columns Tab

Check each of the possible report columns that you want to appear in the main window and in the report.

Change the caption of the column to customize it (for example you can use the term ...Shaft... instead of ...Pile..., or use a localized name)

Fonts Tab

Click to select the font of each report item.

Click [Default] to return to the default ...factory settings....

Tip: Use consistent font styles in the report to achieve a professional-looking report.

Logo Tab

Enter the FULL path of your logo file to make it appear in the final report which comes in RTF format and can be used by most work processors including MS WORD.

The logo file may be saved in most graphics formats. Recommended size is 600 pixels wide and 300 pixels high.

Note: Actual Logo size is calculated for 300 DPI.

For example: your logo is 600 pixels wide X 300 pixels high, it will print as 2... X 1..., regardless of your printer resolution.

Tip: If you plan to send your reports by fax, use a logo design that looks good in Black & White, not a color logo.

Misc. Tab
Unit Code

Note - Only applicable if you have more than one PET unit

This is the prefix of the pile's file name. Use a unique prefix for each unit to avoid conflicting names.

Logger ID

Click to enter the Name/ID of the person doing the field testing.

This will be the default for each new pile

When you select the ...Show this message at startup... option, you will be prompted for the logger ID each time you start the PET software.


Choose to use Metric (SI) or English (Imperial) units

Advanced Tab

This tab allows you to select the colors of the following lines and markers (scroll down for all options):

Average impact line, Grid lines, Length marker, Planned length, Stacked impact lines, Compared pile lines, FFT line, Signal matching calculated pile line, Highlighted Impact color, Amplification line

Scroll down to the bottom to select a virtual keyboard for use with pen driven devices. There is no need to select this option for other touchscreen based devices.


[Tools]-[Signal Options]

Opens the multi-tab Signal options dialog, where you can modify the trigger options, signal convergence, display convention and additional settings.

Trigger tab

This shows the basic impact trigger parameters.

Level in milli-g (mg)

Enter the hammer-tap amplitude [mg] needed to trigger sampling. Only impacts with amplitude higher than this value will be passed to the PET software.

Note: Please do not change this value.


Enter the length of the curve before the top of the trigger pulse.

Sets the amount of data that is kept before the trigger point. The recommended value is 200 cm (2 meters).
Note: Please do not change this value.

Beep at each blow

When checked, the computer will play a short beep sound on each recorded impact.

Trigger + tab

This option shows advanced impact trigger parameters.
All advanced impact trigger options are highly recommended in routine work as they can save considerable amount of labor.
You should however disable these options in hard-to-test cases, where you want to collect any impact, and sort it later in the office.

All features in this tab are Labor saving features

Use smart options

This feature disables all advanced impact trigger options.

Use Smart-Trigger™ quick-reject

When checked, PET will apply an algorithm on each triggered pulse to determine if it is a valid hammer impact, or noise from an unintentional movement of the sensor. The algorithm usually rejects more than 80% of the noise pulses, and accepts 80% of the good ones, so it is recommended to use this feature unless the pile top is badly prepared, and it is hard to get a good hammer impact.

SmartTrigger™ examines the shape of the impact and not just the amplitude. It searches for a trigger shape that is not too wide/narrow and roughly symmetrical. This feature permits PET to use a low and very sensitive trigger level and still ignore random movements and noise.

Auto sort

Check this option to limit the number of collected impacts. When an additional impact is taken, the impacts are sorted and the most irregular one is removed. Using this option will allow you to reduce the amount of post-processing effort in the office later.


Convergence is an indication that enough impacts have been collected, and that additional impacts will not have a significant effect on the average. You can control the accuracy of the convergence in this tab.

Once convergence is reached, a ...Convergence... message will flash across the graph. The message is informational: it does not set a mandatory requirement and you may stop testing before this message appears or continue after it appears.

Average change %

Use this option to select the convergence accuracy. A smaller value means more similar impacts must be collected in order to reach convergence.

Good values to work with are typically in the range of 5-15%.

Number of impacts

Select the minimal number of impacts that must be collected before a convergence can be declared. (3-20)

When sending a less experienced technician to the site, you can set this value to high (for example 30) and ask the technician to collect impacts until convergence is reached. It is always easier to remove bad impacts in the office than to have to go back to the site.

Up / Down tab

There are two popular presentation methods, regarding the polarity of velocities. After getting used to one, it is hard to analyze the others.

There is NO theoretical significance to the direction of presentation; it is simply a matter of habit. The PET software supports both methods.


Down velocities are plotted down - this is recommended as is makes more physical sense.


Up-velocities are plotted on the positive Y-axis

Standards tab

Check this option when operating according to Chinese standards.

[Tools]-[Data Source]

Opens the data source selector dialog, where you can select whether PET uses USB, Bluetooth or a simulated data source. This option is intended for education, demonstration and practice purposes.

See: Connecting the Bluetooth PET to Windows


Choose the User Interface language. We currently fully support English and Spanish, and have partial support for additional languages.

Your language - The software was designed to enable multilingual support. You can add support for your own language by translating a terminology table (the GUI strings). Piletest can compile this into your version of the software - please contact for details.

[Tools]-[Calc and add average pile]

Add a virtual pile to the current sub-site called ...Average.... This ...pile... includes the average impacts of all the piles in the sub-site and it provides an ...average of averages.... This can be processed just like any other pile.

The average piles number is useful for finding project, or sub-site wide features, such as common soil layer interaction or ground-water table interference. You can also use this feature with the 'Compare' option, to compare this average with any other pile reflectogram.

Average only works if all piles in the sub-site are uniform (similar length and age).

[Tools]-[Wave speed Calculator]

Opens the Wave Speed Calculator dialog that allows you to obtain an initial wave speed value, based on concrete age and grade.

See also ...Wave velocity in young concrete...

[Tools]-[ Edit configuration file (advanced)]

Warning: Contact Piletest support before using this option.

Help Menu


Shows PET version number and legal information.


Opens the PET User Manual.

[Help]-[Tip of the day]

Shows the tips dialog.

Note: You are welcome to submit more short tips to for the benefit of the PET users community.


Teaches you how to operate the PET.

Additional Features and Buttons in the Project Window Toolbar

The toolbar provides one-click control to perform common actions:

Pile window

Pile Name

Change the name of the pile, up to 40 characters. You can use localized names.

Note: Two piles in the same sub-site cannot have the same name.


Select the sub-site to locate this pile.

Planned length

Drag the red triangle right or left to set the planned length.

Start / Stop

This is a dual mode button. When the accelerometer is positioned on the pile, press Start to begin collecting hammer impacts.

The impacts will appear in Impacts section in the Pile window below. When you have collected enough hammer impacts press Stop.

Impact tab

  • Amp - to compensate for soil friction until the toe reflection appears the same size as the hammer impact.
  • Auto - Click [A], to set the amplification value automatically
  • Filter - Apply smoothing using the filter (be careful not to overuse this feature)
  • Scale axis - Change the scale of the graph by dragging the scale axis right or left.
  • Sharp - Use sharpening to enhance some features (be careful not to overuse this feature)
  • Length marker - Change the position of the suggested length mark (red marker on the reflectogram axis) by dragging it.
    The PET software automatically sets the length marker at the lowest point of the average reflectogram after each recorded impact.
  • Planned length marker - Drag the top of the Red triangle to mark the planned length of the pile for reference.
  • End-Of-Line Mark - Drag the red square to change the total length of the reflectogram (up to 3 times the initial planned length, but not less than 2 m). The position of the End-Of-Line marker is where the maximal amplification is applied.


Press View to select viewing:

  • Stacked view of impacts.
  • FFT curve - the plot is shown below in green in the reflectogram.
  • Amplification curve - the plot is shown below in light blue in the reflectogram.
  • Impacts panel on the right of the reflectogram.
  • Open the Signal options dialog


Press Compare and select a pile (by pile name) to present. The pile is represented in the reflectogram as a light dotted line (red-colored dotted line in the reflectogram below).

Data tab

When you have finished analyzing the pile test results use the Data tab to classify the pile.

You can set both the certainty of the pile length measurement, and add free text notes to describe the measured results of the pile. You can add additional notes to the notes list (+Add to list) and also remove old notes (-Remove from list)

Length certainty

Click the button to change the reported length. The options are:

  • Normal (a number)
  • Uncertain (a number with a question mark), or
  • Unknown (a question mark only)

For example: (12.3 --> 12.4? --> ?)

This is used to express the uncertainty of the reported length. Any method has limitations, and a good tester is aware of those limitations and uses the certainty tag to show cases where the method is unable to provide results with a high degree of certainty.

Pile Notes

Enter notes which are specific to the pile, for example "Head needs trimming", "Anomaly at 6 m" or "Cannot see toe reflection"

Enter pile notes, or select notes/comments for this pile from the history.

TIP: When editing pile notes, click on the reflectogram to insert the length into the Notes.

Stored Notes

You can store a list of typical notes as templates, to save re-typing them each time.

[+Add to list]

Add the current note to the stored notes list.

[-Remove from list]

Remove the currently selected note from the stored notes list.

TIP: Enter the hash (#) character into a stored note to represent length. This hash character will be replaced by the length you clicked on the reflectogram.

For example: enter and store the note ...Possible necking at #.... Click on the reflectogram at 5.2 m, the text will change to ...Possible necking at 5.2 m...

See additional Labor saving features

Info tab

Use this tab in the pile window to view all the information which identifies this pile.

Press [Export] to export this data to a CSV file for general use, and for documentation and follow up later in the office.

If the pile was tested using the Android app (V2.0 or later) it may contain GPS location and / or a photo of the pile.

Press [Photo]* to view it. You can also insert the photo in the final report. See Customizing PET reports.

Press [Map]* to open the maps application in your Internet browser and show the (recorded) location of the pile.

* This option is only available when the pile was tested using an Android device equipped with a GPS receiver and a camera.

Features by Task

Projects, Sub-sites and Files


PET uses one dedicated folder to store projects. ...Home folder... is the software term for ...A root folder that holds all projects...
...<documents\Pile Testing... is the default path for the home folder.

Projects are stored as sub-folders of the home folder.

Each pile (all impacts and metadata) is stored a separate file (with the extension .PP) under the project folder.

A project folder also contains a file called ...PROJECT.INI..., which is a text file storing the project's titles and other miscellaneous settings

A pile's filename is made up of a unit code, a system-wide unique number and the extension ....PP....

For example: B0000059.PP

  • B is the unit code (Only relevant for users with more than one PET unit)
  • 000059 means this is the 59th pile stored on this system
  • .PP is the file extension

This naming scheme ensures that no two piles will ever get the same file name, and no test work will get overwritten and lost.

For example:

C:users\john\documents\PILE_TESTING   <-- The ...Home folder...
├───1003                              <-- A project
│   ├───A00059.PP                     <-- A pile
│   ├───A00060.PP                     <-- Another pile
│   ├───A00060.JPG                    <-- A photo of the above pile
│   └───PROJECT.INI                   <-- The project settings
├───1004                 <-- Another project


Sub-sites are a way to ...break up... a project into smaller parts that are easier to manage and can produce a clearer report.

For example, if the project contains several buildings, each building can be used as a sub-site. Piles on different buildings may then have the same designation.

Sub-site names are stored in each pile's file. When you open a project, piles are grouped by sub-site.

When the last pile of a sub-site was moved to a different sub-site or deleted, the sub-site is removed. There can be no empty sub-sites.

A new pile in a new project is created in the ...default... sub-site. This name will not appear in the report. If you create a new pile in a new sub-site, PET will suggest that you rename the ...Default... sub-site to a more meaningful name, to avoid confusion.



Starting a new project

  1. From the Main Menu, select [File]-[New project]
  2. Verify that the ...Home folder... points to the correct path
  3. Enter the name or number of the project and click [OK]

PET will create a new folder under the home folder, and will create the file PROJECT.INI

TIP: Use project numbers, rather than names. This makes it easier to find and manage many projects.

Opening an existing project

If the file was created or opened recently, you can find it in the ...most recently used... list under the ...file... menu

  1. From the Main Menu, select [File]-[Open project]
  2. Verify that the ...Home folder... points to the correct path, or click [Home Folder] to change it
  3. Select the project and click [OK]

TIP: The title you give the project is displayed when you look for a project to open.

Deleting, renaming & merging sub-sites

From the Main Menu, select [File]-[Sub-Sites], select the appropriate sub-site and the proper action.

Saving a project

There is no option and no need to save a project as all changes are saved automatically.

Transferring project files to another computer

After the first (or only) visit to the site, copy the folder of the whole project to the target. You can normally do this by dragging the project's folder to the target.

On future visits sort the source folder by date and only copy the latest added files to the target computer.

Sending piles by email

If you only intend to send a small number of files then you can send them all as a single attachment. We recommend that you compress the files using WinZip or a similar file compression program.

Note: Email cannot send or receive large attachments.

Exporting Pile Data to CSV format

After testing a pile, the pile data can be exported to a CSV (Comma Delimited text format) which is readable by most spreadsheet software and text editors. This can be used for research and for exporting to alternative analysis software.

To export the data, first select a pile. In the Pile window, select the Info tab. Click on ...Export... to export the full pile information to CSV format and open your assigned spreadsheet application (such as MS Excel).

PET will create a CSV file by adding the ....CSV... extension to the name of the pile.

An example of the CSV format is shown here:

Pile name:



Tower 2 / PC2


C:\Pile Testing\foobar - 2nd\A0000110.pp




20 impacts

each of 576 samples

at 50.0KHz




















































The first seven rows contain general data about the pile. The following rows show the average data, and each impact value.

Each row is a sample value, with equal time differences defined by the sampling rate (32KHz here).

Sample values are integers. To convert the values to acceleration [g] multiply by 0.000244140625 (=1/1000 hex).

To plot the raw data, select a column, and click the chart icon.

Note: To convert this to a PET-like plot, you will need to implement your own algorithms for example for filtering, and integrating the raw data.

Using the FFT curve

[X] Check the FFT checkbox (in the View Popup menu in the Pile window) of an existing tested pile to show/hide the green FFT curve.


The FFT (Fast Fourier Transform) is a frequency-domain analysis of the time-domain signal.

For simplicity, PET converts frequencies to length (using the current wave speed)

For example, if the wave speed is 4000 m/s, a frequency of 1 KHz is displayed at 2 m.


The FFT curve is usually smooth (with several peaks resulting from the signal shape, and the FFT algorithm).

The FFT curve can sometimes help quantify the location of shallow anomalies. For example, a reflectogram is shown below, with some periodic noise, a sharp peak in the FFT curve is clearly visible, and a possible analysis is a necking at ~2.8 m (which is hard to quantify from the time-domain curve).

Wave speed calculator

From the main menu select [Tools]-[Wave speed Calculator], or, when adding a new pile click on the [Calc] button from the impact tab in the Pile window.

Grade - Drag the black bar to set the specified grade of concrete strength.

Concrete age - Drag the black bar to set the known concrete age.

These two parameters set the expected wave speed in the concrete.

When adding a new pile, the calculated wave speed is automatically used as the wave speed.


Wave speed in a rod is given by c=√(E/ρ). The mass density ρ is determined at the moment of concreting and hence does not change. Young's Modulus E, however, tends to increase as the concrete hardens, albeit at a decreasing rate. As a result, c increases with the age of the concrete.

The relationship between the wave speed (in m/sec) and age for 30 MPa concrete is given by (Amir, 1988):


where t is the concrete age in days. The wave speed c for other concrete grades fc is given by:


It appears that from the age of one week onwards, c lies around the rather narrow limit of 4000m/sec +/- 10%.

Summary of Advanced interpretation techniques


The FFT (Fast Fourier Transform) is a frequency-domain analysis of the time-domain signal - read more...

Average pile

Add a virtual average pile - read more


TODO: brief description - and link to reference

Signal Matching

Signal matching is an advanced analysis technique that helps you guess a possible pile profile. read more...

Customizing PET reports

The PET software provides many different options that enable you to customize your report.

Add your logo


Most graphics formats are accepted


Add a title and a sub-title,

The titles are saved in the project.ini file, in the project folder.

Column width

Modify the column widths by dragging the column separator so that (for example) the ...Details... and the "Date" columns don't wrap to two lines, and so that the chart is as wide as you need it to be.

Row height

[Pile]-[Modify all]

Change the row height to 200-300%

You may also select specific piles to get a higher row by dragging the separator between rows.

Row height may be overridden just before printing, in the print dialog [File]-[Report].

Chart options


This option enables you to change the colors and pen width of the chart lines.

Hide unused fields


If you do not have any comments, you can leave out and hide the ...Remarks... column altogether. You can do this with any other column as well.

This option also allows you to select which details you want to include in the report "details" column.

Fonts, Captions


This option enables you to change the column captions and their fonts.

This option also allows you to localize (translate) the captions if you need to localize the report to any language other than the default.

VIP (Very Important Piles)

This option is intended for specific piles that have anomalies and require special detail - report one pile per page (in the print dialog).


When piles are logged using an Android device with the Bluetooth PET, you can take a photo for any pile.

When you report using the VIP mode (one page per pile), this photo is included in the report.

Note: to reduce the file size the photo is linked to the report, not saved in it. When you send the file, first select [Edit]-[Link]-[Break link] in MS Word.

Margins, paper size

[File]-[Page setup]

This option enables you to select the page margins of your report.

[File]-[Print setup]

This option enables you to open the default printer settings dialog.

PET advisor

The PET advisor (displayed as a light bulb) is a set of automatic checks run by the PET software on the data you have collected, advising you of potential errors.

The PET advisor cannot check for every possible mistake, and is only intended to help you by providing hints and suggestions. The PET advisor is not a replacement for careful analysis, but can help you find accidental errors in your report before you submit it.

Here are some of the hints the PET advisor may provide:

  • Irregular impacts - when the impact traces seem to be irregular
  • High Filter value - when the Filter value is too high
  • Pile too long/short - when there is a large gap between the planned and measured lengths
  • Length mark beyond end-of-line
  • Scale too small - when the scale isn't large enough to show the length mark, planned length or end-of-line

There are currently more than 15 different automatic checks that the PET advisor runs on each pile.

Labor saving features

The following pile-testing features are optional, however when you begin using them in full you will work much more efficiently.

On-screen keyboard

This is useful if you are using tablet computer. The on-screen keyboard option provides a full/numeric keyboard, just when and where you need it. You can enable this feature from the Options menu.


This feature enables you to apply wave speed, reporting row height, and other settings to all piles, instead of one-by-one. This feature can be accessed from the Modify All dialog.

Insert multiple piles

If you need to test a large number of piles in a retaining wall numbered 1 to 100 for example you can use the ...Add multiple piles... feature. This feature can be accessed from the Pile tab on the top menu.


When you print a report from the PET software creates an RTF (Rich Text Format) file and opens it using your word processing software, instead of printed it to paper. This enables you to perform any last-minute final customizations, and merge your report with other documents, an e-fax or email.


As soon as a sufficient number of impacts have been performed, performing additional impacts has only a marginal effect on the average result. Use the Convergence options to accurately define just how many impacts are ...enough....


Why keep irregular impacts? With Auto-Sort you can set the desired numbers of impacts to collect. Once this number is reached, the impacts are sorted and the most irregular one are removed to the recycle bin.

Smart trigger

When moving around the pile head, many false impacts are triggered by random accelerometer movement. The SmartTrigger looks at the trigger shape, and removes >80% of the false triggers, while passing >80% of the good ones.

Sort impacts

After you have collected a large number of impacts, the next step is to remove the irregular impacts. Click the ...sort... button to sort the impacts by their abnormality (...distance... from the average). The abnormal impacts are then moved to the top of the stack making is easier for you to remove them. The Auto-Sort feature performs the same task automatically.

Notes standard

To avoid having to type the same notes over and over again for many piles, click on the [Data] tab and build up your own custom notes list that you can use as templates.

Contacting Piletest

As a new user we try to support you as best we can. Your success is our success. Please do not hesitate to contact us whenever necessary.

Piletest engineers will help you:

  • Create your first report
  • Review and modify your second report
  • Review additional reports, until you are confident to continue on your own
  • Review any additional interesting or unusual cases

All of the above is part of SOS support program, complimentary with every new PET purchase.

To get support:

  • Select [File]-[Consult with Piletest]


  • Email - attach the raw data archive, and any additional information such as soil profile, drilling method, groundwater table, etc... The more details you can provide, the better.

PET for Android android_logo_small.png


The 'PET - Pile Echo Tester' is an Android application (henceforth App) that you can install from the Google Play Store. The App runs on almost any Android device and connects to the PET Bluetooth hardware for use as a convenient data collector.

The main focus of the App is ease of use and productivity. The App is not intended for advanced analysis or reporting.

The main features of the app are:

  • OS: The Android PET App runs on most Android devices, with Android SW version 4.1 and higher. No iPhone support is provided.
  • HW: The Android PET connects only to the PET Bluetooth hardware. There is no support for the PET USB hardware.
  • Data: The logged data is identical in quality and format to the data collected by USB PET version for Windows.
  • Goal: The Android PET is intended only for field data collection, and does not provide advanced analysis, or reporting capabilities.


Search for, download and install the PET - Pile Echo Tester App from Google Play.

We recommended that you select the installation as an [Automatic upgrade] so that you will get new versions automatically.


Projects list

The main window of the App displays the projects list. Each row shows the project name, title and number of piles.

The first time you use the App you will see a pre-install "Example" project with just one pile.

Click on:

  • A project row to open it
  • The top [Wrench] icon - to open the Options Window
  • The (+) icon to add a project

Project window

The project window shows the project piles.

The title line shows the project name and the total number of piles.

Each row displays the name, measured length and test date of a pile.

Click on:

  • The [Wrench] icon - to open the Options window
  • The [?] icon - to see project summary
  • The [Share] icon - to zip and share the project (Sharing options depend on your device and may include mail, Bluetooth and more)
  • The [Titles] header - to edit the Title, and Sub-title, or to select a sub-site
  • A pile row - to open it for additional processing or testing
  • The (+) icon - to add a pile

Press and hold a pile row to display the following menu:

[X] Delete - to delete a pile from the project

(i) Information - to show pile info

(?) - to see a project summary

[Share icon] - to zip and share the project

Pile window

Double-click on a pile row to open the pile details window, and display the reflectogram.

The Pile window shows one pile at a time, with all controls needed for basic field analysis.

This window was designed to give you enough control to allow you to leave the site with enough high-quality information.

There is a row of control buttons at the top of the screen. You can drag the button bar left or right to view more options. The control buttons are:

[Reset] [Options] [Name] [Subsite] [Notes] [Camera] [Wave speed] [Wave speed Calculator] [Filter] [Sharp] [Map] [Delete] [Undelete] [Exit without saving]

Buttons and controls

This section describes the function of the buttons and controls in the Pile Window.

Start testing

  1. Put your Bluetooth PET sensor in "discoverable" mode (LED Heartbeats) and click the [Start] button. See LED Indications.
    The icon changes to an hour glass.
  2. The app will now provide connection instructions to the Bluetooth PET sensor, including initial pairing (PIN is 1234).
    If the device is already paired with the sensor, it will connect immediately

  1. Once connected, start tapping normally to collect impacts.

When a connection has been established the app will open the device location hardware (GPS) and will add the location and accuracy data to the file.

Note: Please remember that the recorded location is of the device and not the sensor or the pile.

See Geo-Tagging


Click this button to erase all impacts and begin again.

Note: To prevent accidental deletion, you need to press and hold this button to delete all impacts.


Click this button to open the settings dialog.

Pile Name

Click this button to enter a name for the Pile.


Click this button to select the pile sub-site or create a new sub-site.

Pile picture

Click this button to take a photo of the pile using the camera in your mobile device. The photo will have the exact same name as the pile, with the .JPG extension, and it is stored on the same folder.

Wave speed

Click this button to change the wave speed (Multiples of 50m/s).

Click this button to open the wave speed calculator.

Press the + and - buttons on the right and left to set the Age and the Grade of the concrete. This will automatically update the Wave speed relevant for the specified concrete type of concrete. Press OK to apply the changes.


Click this button to change the filter value by pressing the + and - buttons.


Click this button to change the sharpness value by pressing the + and - buttons.

GPS location

Click this button to open the map application on your mobile phone, and store the location of the pile.

Selecting impacts

Click this button to add pile notes.

Click this button to move the highlighted impact to the recycle bin.
To highlight an irregular impact, simply tap on it the line in the graph where there no other controls.

Click this button to restore the last deleted impact from the recycle bin.

Click this button to exit the pile window, and return to the project window without saving your work.

Note: To prevent accidental loss of data, you need to press and hold this button to exit without saving.

The following section describes the pile window functions


Drag the Amp drawer up and down to change amplification value.

Tip: Once started to drag, you may move your finger to the right to see the values.

Planned length

Drag the triangle to the desired depth planned length value.

Pile length

Drag the vertical line to modify the automatically-selected measured length of the pile.

End of Line marker

Drag the square to set the location of the end-of-line mark.

Reflectogram scale

Drag the scale right or left to change the scale value.

Options menu

Use SmartTrigger

Use this to option to enable or disable the SmartTrigger option.

AutoSort settings

Use this to option to modify the AutoSort settings.


Use this to option to select Metric/Imperial (UK or US) units.

Reflectogram direction

Use this to option to swaps the direction of the reflectogram up or down.

Color Scheme

Use this to option to select a brighter color scheme for improved outdoor visibility under direct sunlight (Recommended).

Use Sound Effects

When this option is checked, The App will use special sounds for:

  • Accepted impacts
  • Rejected impacts by smartTrigger (the device will also vibrate, if available)
  • Rejected impacts by AutoSort (the device will also vibrate, if available)
  • Sensor connected
  • Sensor disconnected

TIP: In a noisy building site, it is almost impossible to hear the device sounds. Consider using a Bluetooth earpiece.

Home folder

Select a folder on your device where all projects are located. By default this is [Pile testing]. See Projects, Sub-sites and files.

DropBox integration

Click to link (or unlink) your device using DropBox.

Once linked, each time you save a pile, it is also synced to your Dropbox.

The project will be available under \<your Dropbox folder>\Apps\Piletest.PET\<Project name>

DropBox integration has two advantages:

  1. It provides you with a seamless backup
  2. The backup is automatic

About PET

This button shows the App version, copyright information, a link to web site and a link to the Google App store where you can rate the PET App ★★★★★.


Appendix 1 - Theoretical Background

Stress-wave Theory

When we have completed testing our piles we still need to analyze the results and reach some conclusions regarding the acceptability of the length, continuity and changes in cross-section of the pile. To understand the meaning of our reflectograms, we must first look into some basic principles of one-dimensional stress-wave propagation.

Wave Propagation in Elastic Rods

When we strike the top of the pile with the hammer, we create a compression stress-wave that moves downwards.

The analysis of wave propagation in piles is fairly straightforward, provided we make a few reasonable assumptions:

  • The pile is prismatic (or cylindrical), with cross-section A, elastic with Young's Modulus E and homogeneous with mass density ρ.
  • The wavelength is larger than the lateral dimension of the rod.
  • Cross sections remain plane, parallel and uniformly stressed.
  • Lateral inertia effects are negligible

Let us now examine an element along the rod (Figure 1). If we denote the stress above the element by σ and below the element by σ + (∂σ/∂x) Δx, the unbalanced force on the element is (∂σ/∂x)Δx. According to Newton's second law (force equals mass times acceleration):

\Large A\left(\frac{\partial\sigma}{\partial X}\right)\cdot\Delta x = A\cdot\Delta x\cdot\rho\left(\frac{\partial^2u}{\partial t^2}\right)\ \ \ \ \ \ \ (1)


 Because of elasticity,

\Large \sigma=E\cdot \frac{\partial u}{\partial x}\ \ \ \ \ \ \ (2)

Substituting σ and eliminating both A and Δx on both sides of equation (1), we get:

\Large E\cdot\frac{\partial^2 u}{\partial x^2} = \rho\frac{\partial^2 u}{\partial t^2}\ \ \ \ \ \ \ (3)

\Large \frac{\partial^2 u}{\partial t^2} = C^2\cdot\frac{\partial^2 u}{\partial x^2}\ \ \ \ \ \ \ (4)

This is the one-dimensional wave equation for a prismatic rod. c = √(E/ρ) is the speed of wave propagation in the rod as distinct from v = ∂u/∂t which is the particle velocity.

Figure 1: Wave propagation in an elastic rod

Using Hooke's Law, we can show that the force P acting on a given plane is proportional to the particle velocity v:

\Large P = Z\cdot v\ \ \ \ \ \ \ (5)

The coefficient Z = Acρ is called the impedance, with typically measured in kg/sec. Alternative expressions for Z are A·√(Eρ) and E·A/c.

Reflection from the end

When waves propagate in a finite rod, they will eventually reach the end. The wave will then be reflected back, with the nature of the reflection depending on the boundary conditions at the end: When the end is fixed, the wave will be reflected unchanged, that is a compressive wave will be reflected as compressive, and vice versa. On the other hand, a wave reflected from a free end will change sign from compressive to tensile, and vice versa.

If we take a prismatic rod with a given length L, and apply a short duration (dynamic) load to one end, the wave created will travel along the rod and return from the other end. The duration of the whole trip is T = 2·L/c.

Discontinuities in rods

A discontinuity in a rod is defined as an abrupt change in either cross-section (From A1 to A2) or material properties E and ρ. When a wave traveling in a rod meets such a discontinuity, a part of it will be reflected back while another part will be transmitted beyond the discontinuity (Figure 2). Let us represent the incident wave parameters by the index i, while r and t will denote the reflected and transmitted waves, respectively.

Figure 2: A rod with a discontinuity

From equilibrium and continuity considerations, we can get the following relationships:

gif.latex   (6)


gif.latex   (7)

These two equations enable us to calculate the behavior of a wave as it moves along a rod of an arbitrary shape. A convenient way to visualize the process is to represent the wave propagation in the x-t plane. The lines on this plane describing the propagation of longitudinal waves in a rod are called characteristics.

Figure 3 shows the characteristics for a rod with a reduced cross-section. The figures beside the lines are the respective stresses, calculated from equations (6) and (7).

Using the characteristics method, we can draw a graph showing the wave speed at the top of the pile versus time. Such a graph (Figure 3) is called a reflectogram.

Figure 3:

Characteristics for a rod with a reduced cross-section

(Courtesy of Vyncke & van Nieuwenburg 1987)


The above analysis of wave phenomena in prismatic rods was based on the assumption of zero skin friction. However when the rod is embedded in solid material, the situation changes. The rod particle displacement, which is associated with the wave, will give rise to skin friction forces in the opposite direction. To visualize the effect of these forces, let us consider the case of a compressive wave traveling downwards in a rod (Figure 4). As the wave passes the point x = a, it gives rise to a friction force F acting upwards.

For the sake of simplicity, let us assume an elastic, linear friction model.

The friction force F gives rise to a pair of waves, each equal in magnitude to F/2: A reflected wave and a transmitted wave. The reflected wave is of the same type of the incident wave. A compressive wave will cause a compressive reflection, and vice versa. Thus, the reflection due to skin friction has a similar effect to an increase in the impedance.

The transmitted component is superposed on the incident wave. Since it is of opposite sign, the net result is a weakening, or damping, of the wave. The total energy in the rod is decreased by friction, the difference being radiated to the surrounding medium.

Figure 4: Skin friction

Appendix 2 - PET length markers

There are three length marks in the pile window

Reflectogram window screenshot
  • The red vertical line is the MEASURED length (length marker)
    • The measured length marker should be placed on a reflection which represents the toe of the pile.
      This will also appears in:
      • The project window summarizing all the piles in the project
      • The report table
      • The report summary table
  • The red triangle at the top is the PLANNED length
    • The planned length should be set before starting to test - it will automatically set the sample duration, scale and end-of-line mark to good default values
    • Use this mark for reference of expected length, when viewing the reflectogram
    • The planned length optionally appears in the report
    • The planned length will also allow you to quickly identify a length anomaly.
  • The rightmost red square is the END-OF-LINE length
    • At the end-of-line the amplification is maximal
    • This marker should be set a few meters beyond the planned length (triangle marker). Only then the Impact parameters (see below) of Amplification, Filter, Sharp, Speed should be adjusted to improve the viewed results
    • The end-of-line value does not appear in any report

Appendix 3 - Beginner's guide to PET Analysis

A step-by-step guide for PET results analysis

Important Note: The following procedure is only a demonstration of what we at consider good testing practice and is no substitute for sound engineering judgment. Any conclusions and/or recommendations based on the test results are the sole responsibility of the user.

Basic Analysis

  1. If you have reliable information regarding the age of the pile and the grade of the concrete use the wave speed calculator to set the speed, otherwise use a wave speed of 4000m/s as a rough default, and expect 10-15% offset of the measured length. The wave speed can be revised later in the office.
  2. Set the Amplification (Amp) to 1.0 (=no amplification), check for impacts with abnormal trigger shape and delete them.

Note: Deleted impacts actually remain in the pile's recycle bin and may be un-deleted at any time.

You should be left with a good number of similar impacts, 10 or more is ok, 3 is the absolute minimum.

  1. Drag the end-of-line mark (red square) to a few meters beyond the expected length.
  2. Set the filter and sharp values to their maximum values.
  3. Increase the amplification until you see a clear toe reflection.
    Typical Amplification values are length (m) X 5 to length (m) X 15, but this can vary considerably.
  4. If you see a possible toe reflection, drag the length mark to that point.

Note: If the piles are perfectly rock-socketed, the toe reflection is expected to be in the direction opposite of the trigger.

Tip: In short piles with low friction you can try to increase the scale and end-of-line mark to more than twice the expected length, and look for a second reflection from the toe. In hard soils or long piles you will not normally see a second reflection.

If you do see a second reflection, it gives you a higher certainty of the location of the length marker.

Tip: If you have a difficult case with just a few good impacts, delete and undelete impacts to see the effect on the average

  1. If you still cannot find a clear toe reflection, try to expand your search to a few meters before or after the expected length. If nothing is visible, the reasons might be:
  • Pile is beyond the limitations of the method (too slender, too much friction).
    You can note this in the report as follows: ...Could not see toe reflection...
  • Head was not clean enough.
    You can note this in the report as follows: ...Head not clean, could not see toe reflection, re-test recommended...
  • Concrete too young. Normally, a test should be performed with concrete at least 5 days old, try to repeat the test in a week to get better results).
    You can note this in the report as follows: ...Could not see toe reflection, re-test recommended...
  • Test was not performed well, hitting loose/wet concrete, water, etc.

  1. Set the filter and sharp values to zero and look for additional features before the end of the pile.

At this point you see:

  • Repetitive noise

The FFT curve may show you the location of the reflector. Depending on the severity of the reflections, consider mentioning this in the report.
You can note this in the report as follows: ...A reflection at 1.9m.... This is typical for cased drilling.

Pilewave Example

  • Necking

This appears as an early reflection, in the same direction as the toe reflection.

Pilewave Example

Tip: shallow necking might show additional reflections, all in the same direction as the trigger.
Tip: Be careful - a second reflection from a necking in the middle of the pile can sometimes be confused with a toe reflection.

You can note this in the report as follows: ...(severe/slight) necking at _._ m...

  • Bulging

This appears as an early reflection in the direction opposite to the trigger.

Pilewave Example

Tip: Shallow bulging may show additional reflections, with alternating directions. This might be confusing.
Tip: Be careful. A second reflection from bulging in the middle of the pile can sometimes be confused with a toe reflection/necking.

You can note this in the report as follows: ...(severe/slight) bulging at _._ m...

  • Short piles

Short piles are simply piles with an early toe reflection. You can note this in the report as follows: ...Short....

  1. Finally, set Filter and Sharp to reasonable values that show the main features and do not hide information.

Tip: Do not overdo filtering and sharpening.

Advanced Analysis

Average pile

Contact us for details

Compare piles

Contact us for details

Signal matching

Contact us for details

Appendix 4 - Reporting Errors (bugs)

When the software encounters an error (bug), the following screen may pop-up.

Please send us feedback about the problem using this form, so that we can improve the PET software for you. You will continue to receive free PET software upgrades for 10 years!

Appendix 5 - Troubleshooting

When you press [Start] A message ...USB PET could not be found...... appears, even though the plug is inserted.

Check the following:

  • Make sure the hardware drivers are installed
  • Separate elements: Make sure your PC USB port is operational by plugging a disk-on-key or similar device to the port, plug the PET into a different PC (even without PET installed) to see the ...New hardware wizard....
  • Start ...device manager... ([Start]-[My computer]-right click-[Properties]-[Hardware tab]-[Device manager].
  • Scroll down the ...Universal serial bus controllers... and locate the PET. If you see an ...unrecognized device..., right-click on the device and try to reinstall the driver.

When hitting the pile, I hear beeps, but no impact is recorded

This indicates that the impacts are strong enough, but are rejected by the smart trigger. To fix this, check the following:

  • Hit softer: you should hit sharply, lightly (equivalent to dropping the hammer from 10-20 cm) and frequently (~2 times per second)
  • Find a different spot for the sensor or hammer, make sure you do not hit a slurry mixture or loose concrete.
  • Clean or trim the pile head
  • Disable ...Smart Trigger...: under difficult conditions, it is hard to get any good impacts. In this case it may be faster to disable the smart trigger and sort the impacts manually . Remember to re-activate the smart trigger when you are done.
  • Trigger Level: Typically, a trigger level of 0.4g is just right. However, this level can be decreased to make the PET more sensitive, or increased to make it respond only to a stronger impact.

Impacts are very irregular

To fix this, check the following:

  • Find a different spot for the sensor or hammer, make sure you do not hit a slurry mixture or loose concrete.
  • Clean or trim the pile head.
  • In extreme cases, prepare a testing surface and smooth it with a disk grinder.

The system records impacts without hitting the pile:

  • Trigger Level might be set too low. Typically 0.4g is just right.
  • The system might be using the ...Demo... data source.

Appendix 6 - Software Upgrades

Piletest occasionally releases free software upgrades which include accumulated bug fixes, new innovations and usability improvements.


The PET software automatically checks for a new version and will notify you as follows:

Select [Upgrade now] to close the PET software and to be redirected to the download page of the Piletest website.

PET software upgrades are:

  1. Fast
  2. Do not require you to uninstall the previous version
  3. Are always backwards-compatible - can read files from any previous version.


New versions of Android PET will be released periodically on the Google Play Store.

If you selected the option "Upgrade Automatically" when you installed the PET App, then the App will be upgraded automatically. If you did not select this option the Play Store will notify you of the availability of a new upgrade that you can download and install.

Appendix 7 - Technical Specifications







Temperature range


Industrial-grade transducer enclosed in a durable stainless steel housing

30mm (diameter) x 90mm (Length)

120gr (Transducer)

2.3kg (Shipping)

-20C to +55C (Operating)

-40C to +80C (Storage)

Computer USB port




Resonance frequency

Sampling frequency

Sampling resolution


Within 1%, 0 to 50g





ASTM D5882-07 (2013)

Meets or exceeds


Pile lengths



2m to 80m (depending on diameter and soil profile)

Up to 100 piles/hour by a single operator (under favorable conditions)


Computer Requirements

Computer is NOT INCLUDED

Recommended: Tablet PC (with outdoor display such as the Toughbook or Toughpad by Panasonic)





Windows XP, 7, 8, 8.1, 10

32 or 64 bit processor

800x600 resolution or higher

 USB Port

PET Bluetooth





Temperature range



Industrial-grade transducer enclosed in highly durable polycarbonate plastic (Lexan)

34mm (diameter) x 120mm (Length)

155gr (Transducer)

3kg (Shipping)

-20C to +55C (Operating)

-40C to +80C (Storage)


(Protection against complete submersion in water)

2 AAA Alkaline batteries, 3V total. Sufficient for

testing approximately 300 piles




Resonance frequency

Sampling frequency

Sampling resolution


Within 1%, 0 to 50g





ASTM D5882-07 (2013)

Meets or exceeds this standard


Pile lengths



Wireless range

2m to 80m

(depending on diameter and soil profile)

Up to 100 piles/hour by a single operator

(under favorable conditions)


Up to 10 meters between transducer and computer

Computer Requirements

Computer is NOT INCLUDED

Recommended: Tablet PC (outdoor display such as the Toughbook or Toughpad by Panasonic)




Wireless Interface

Windows XP, 7, 8, 8.1, 10

32 or 64 bit processor

800x600 resolution or higher

Bluetooth 1.0 or higher

For PET Bluetooth version - Bluetooth antenna on tablet or PC or Android 4.0 or higher device with Bluetooth support.