Dakota Ultrasonics PVX-B Operating Manual

OPERATION MANUAL

DAKOTA ULTRASONICS

PPVVXX--BB

Precision Visual Thickness Gauge

P/N P-195-0002 Rev 1.0, September 2014

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CHAPTER ONE INTRODUCTION ...................................................................... 1

CHAPTER TWO QUICK STARTUP GUIDE ....................................................... 2

CHAPTER THREE KEYBOARD, MENU, & CONNECTOR REFERENCE ....... 11

CHAPTER FOUR PRINCIPALS OF ULTRASONIC MEASUREMENT ............ 20

CHAPTER FIVE SELECTING THE MEASUREMENT MODE .......................... 23

CHAPTER SIX MAKING MEASUREMENTS .................................................... 26

CHAPTER SEVEN USING THE DIGITS & B-SCAN DISPLAYS ...................... 38

CHAPTER EIGHT THRU PAINT MEASUREMENT TECHNIQUE ................... 51

CHAPTER NINE ADDITIONAL FEATURES OF THE PVX-B ........................... 52

CHAPTER TEN DATA STORAGE – SETUP, EDIT, & VIEW GRIDS ............... 57

CHAPTER ELEVEN SETUPS – CREATE, STORE, EDIT, & RECALL ............ 74

CHAPTER TWELVE USING THE UTILITY SOFTWARE ................................. 81

APPENDIX A - VELOCITY TABLE ................................................................... 82

APPENDIX B - SETUP LIBRARY ..................................................................... 84

CHAPTER ONE INTRODUCTION

The Dakota Ultrasonics model PVX-B is a precision ultrasonic thickness gauge with a time based B-Scan and alpha numeric data logger. Based on the same operating principles as SONAR, the PVX-B is capable of measuring the thickness of various materials with accuracy as high as  0.0001 inches, or  0.001 millimeters. The principle advantage of ultrasonic measurement over traditional methods is that ultrasonic measurements can be performed with access to only one side material being measured.

Dakota Ultrasonics maintains a customer support resource in order to assist users with questions or difficulties not covered in this manual. Customer support may be reached at any of the following:

of the

Dakota Ultrasonics Corporation 1500 Green Hills Road, #107 Scotts Valley, CA 95066 USA Telephone: (831) 431-9722 Facsimile: (831) 431-9723 www.dakotaultrasonics.com

1.1 Disclaimer

The PVX-B is a full-featured precision thickness gauge with a great deal of features and measurement modes allowing a great deal of control over the functionality and electronic performance of the instrument. As this provides the user greater control and versatility for a variety of applications, it also requires that the user be comfortable with the operation of these features and modes when operating the instrument. It is strongly recommended that the contents of this manual be read in its entirety. It is also recommended that a sufficient amount of time be allocated to working with the instrument in a test environment prior to use in the field. Responsibility for proper use of the instrument and recognition of this phenomenon rest solely with the user of the instrument.

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CHAPTER TWO QUICK STARTUP GUIDE

Turn the PVX-B on and off using the switch located on the bottom right corner of the keypad. When PVX-B is initially turned on, a flash logo and blinking lights will be displayed prior to entering into the main measurement screen. Note: This section is primarily written as a basic startup guide only.

2.1 Selecting the Transducer Type

The first step in using the PVX-B is to select the transducer type stored in a setup. There are 18 factory setups containing different transducer types that can be loaded, modified and stored in a new setup location. By selecting the transducer type from a predefined setup list, the PVX-B can recall specific properties about the transducer, setup the display area and predefined scope settings. Note: Once the transducer has been selected, the PVX-B will store and recall this setup, containing the transducer type, every time the PVX-B is powered on/off. This setup will only change if the user physically selects another setup from the list. Therefore, if you have previously gone through this section and selected the appropriate setup, proceed to the next section. Use the following steps to select your setup (transducer type):

Selecting a Setup for use with a specific Transducer Type

1) Press the MULTI MODE key once to activate the load setup list containing the transducer types and settings.

2) Use the UP and DOWN arrow keys to scroll through the setup list until the target setup is highlighted.

PVX-B Precision Visual Thickness Gauge

3) Press the ENTER key to display the confirmation screen.

4) Press the OK key to select the setup and return to the measure screen, or

ESC to cancel the selecting a setup.

2.2 Calibration

The next step is to calibrate the PVX-B to the material and transducer being used. If a sound velocity is not known, the PVX-B can be calibrated to a known thickness sample. This demo will briefly explain each of possible calibration techniques. Read through the various calibration techniques and select one of the following:

Known Velocity

If the material velocity is known, the user may wish to simply enter the velocity number into the PVX-B, rather than have the PVX-B calculate the velocity value using a know thickness. The steps for entering the velocity are outlined below:

Using a Known Material Velocity

1) Press the MENU key once to activate the menu items tab. Press the MENU key multiple times to tab right and the ESC key multiple times to tab left until the CAL menu is highlighted and displaying the submenu items.

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2) Use the UP and DOWN arrow keys to scroll through the sub menu items until VELOCITY is highlighted.

3) Press the ENTER key to display the Digits Edit Box.

4) Press the UP and DOWN arrow keys to scroll the highlighted value.

5) Press the LEFT and RIGHT arrow keys to scroll the digit locations.

6) Repeat steps 4 & 5 until the velocity number is correctly displayed.

7) Press the OK key to set the velocity and return to the menu screen, or ESC to cancel entering the velocity.

8) Finally, press the MEAS key to return to the measurement screen and begin taking readings.

Known Thickness

Sometimes the sound velocity of a material is not known. In this case a sample with a known thickness can be used to determine the sound velocity. It would be very handy to carry a set of mechanical calipers to use in conjunction with the PVX-B for calibration in the field:

Using a Known Thickness

PVX-B Precision Visual Thickness Gauge

1) Physically measure an exact sample of the material or a location directly on the material to be measured using a set of calipers or a digital micrometer.

2) Apply a drop of couplant on the transducer and place the transducer in steady contact with the sample or actual test material. Be sure that the reading is stable and the repeatability indicator, in the top left corner of the display, is fully lit and stable. Press the MENU key once to activate the menu items tab. Press the MENU key multiple times to tab right and the ESC key multiple times to tab left until the CAL menu is highlighted and displaying the submenu items.

3) Use the UP and DOWN arrow keys to scroll through the sub menu items until ONE POINT is highlighted.

4) Press the ENTER key to display the Digits Edit Box.

5) Press the UP and DOWN arrow keys to scroll the highlighted value.

6) Press the LEFT and RIGHT arrow keys to scroll the digit locations.

7) Repeat steps 5 & 6 until the known thickness value is correctly displayed.

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8) Press the OK key to calculate the velocity and return to the menu screen, or ESC to cancel entering the velocity.

9) Finally, press the MEAS key to return to the measurement screen and begin taking readings.

Note: CHECK YOUR CALIBRATION! Place the transducer back on the calibration point. The thickness reading should now match the known thickness. If the thickness is not correct, repeat the steps above.

PVX-B Precision Visual Thickness Gauge

Basic Material Type

If the material velocity is unknown, and a sample thickness cannot be taken from the material, the user may opt to choose a basic material type from a list with approximate velocity numbers. It’s important to note that these velocities will not always be an exact representation of the material being tested. Use these values only if a close approximation is acceptable. Follow the steps below to select a basic material type:

Selecting a Basic Material Type

2) Use the UP and DOWN arrow keys to scroll through the sub menu items until MATERIAL is highlighted.

3) Press the ENTER key to display the list of material types.

4) Press the UP and DOWN arrow keys to scroll through the material list until the appropriate material is highlighted.

5) Press the ENTER key to display the confirmation screen.

6) Press the OK key to select the material and return to the menu screen, or ESC to cancel the material selection.

7) Finally, press the MEAS key to return to the measurement screen and begin taking readings.

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2.3 Measure

The PVX-B is now ready to measure. There are two different measurement view options, each with a specific purpose. The steps below outline how to toggle between the different view mode options:

Selecting the Measurement View Option

1) Press the MENU key once to activate the menu items tab. Press the MENU key multiple times to tab right and the ESC key multiple times to tab left until the DISP menu is highlighted and displaying the submenu items.

2) Use the UP and DOWN arrow keys to scroll through the sub menu items until VIEW is highlighted.

3) Use the LEFT and RIGHT arrow keys to scroll the view options.

4) Once the view is displayed, press the MEAS key to return to measurement mode.

DIGITS: Is a general digital view of the thickness value using a larger font size.

BSCAN: The Time Based B-Scan provides the user with a cross sectional view of

the material being tested. This mode is useful when there is concern regarding the profile of the blind surface.

Once the view has been selected according to the application requirements, the BSCAN START (B-ST) and BSCAN DEPTH (B-DEP) of the screen will potentially need to be adjusted if the view has been set to BSCAN. Use the following steps to adjust these settings directly from the measurement screen as follows:

PVX-B Precision Visual Thickness Gauge

Adjusting the Start (B-ST) & Depth (B-DEP)

1) Press the MEAS key once to activate the measure menu items. Press the MEAS key multiple times to move right and the ESC key multiple times to

move left, until the either the B-ST or B-DEP cell is highlighted.

2) Use the UP, DOWN, LEFT, or RIGHT arrow keys to scroll the DELAY and WIDTH values.

3) Repeat steps 1 & 2 until the range is correctly being displayed.

Alternatively, the B-ST and B-DEP values can be changed using the Digit Edit Box as follows:

1) Press the MEAS key once to activate measure menu items. Press the MEAS key multiple times to move right and the ESC key multiple times to move left, until the either the B-ST or B-DEP cell is highlighted.

2) Press the ENTER key to display the digits edit box.

3) Press the UP and DOWN arrow keys to scroll the highlighted value.

4) Press the LEFT and RIGHT arrow keys to scroll the digit locations.

5) Repeat steps 3 & 4 until the B-ST or B-DEP value is correctly displayed.

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6) Press the OK key to set the B-ST and B-DEP value and return to the measure screen, or ESC to cancel entering the B-ST or B-DEP value.

7) Finally, press the MEAS key to return to the measurement screen and begin taking readings.

Note: The B-ST & B-DEP can also be adjusted from the menu tab items. However, using the hot menu keys is the easiest method.

In the upper left corner of each of the mode photos above, is the repeatability indicator. The repeatability indicator is represented by six vertical bars and represents how repeatable the measurements are. In regular measurement mode, the PVX-B makes 4 measurements a second. In scan mode, the PVX-B makes 32 measurements a second. When the PVX-B is idle, only the left vertical bar and the underline will be displayed. However, when the PVX-B is making a measurement, five or six of the bars should be displayed on the repeatability indicator. If fewer than five bars are showing, the PVX-B is having difficulty achieving a stable measurement and the thickness value displayed is potentially be unstable.

DIGITS B-SCAN

CHAPTER THREE KEYBOARD, MENU, & CONNECTOR REFERENCE

3.1 Menu Key (Operation & Sub Menus )

The Menu key activates the primary menu structure containing 9 menu tab groups. These tab groups then contain sub menu items, or functions. The sub menu items have been organized in tab groups according to how closely they are related to the individual tab group names. Let’s first get familiar with how to move around in these tabs before continuing on to the sub menu functions. This procedure is outlined below:

Activating and Getting Around in the Menu Items

1) Press the MENU key once to activate the menu items tab. Press the MENU key multiple times to tab right, and the ESC key multiple times to tab left until the desired tab group is highlighted and displaying the submenu items.

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Now that your familiar with activating and moving amongst the tab groups, let’s have a look at how to move around in the sub menu items as follows:

Getting Around in the Sub Menu Items

1) Use the UP and DOWN arrow keys to scroll through the sub menu items until the desired function is highlighted.

2) Depending on which function is highlighted, use the LEFT, RIGHT, and Enter keys to scroll the options or activate the Digit Edit and List Box options.

The sections to follow will provide the user with an explanation of the sub menu functions:

3.2 Probe – Menu

Zero: The PVX-B is zeroed in much the same way that a mechanical micrometer is

zeroed. If the PVX-B is not zeroed correctly, all of the measurements made using the PVX-B may be in error by some fixed value. Refer to the section on page 29, for an explanation of this important procedure.

Note: This function is only used when using a contact style transducer with a pulseecho contact setup selected. All the other transducer types use multiple echo modes, and the zero function is not needed.

Gain:

the volume up or down on a stereo receiver. Refer to page 48 for further info.

AGC:

interface-echo and echo-echo modes only. This is much like turning the volume up or down on a stereo receiver. However, the PVX-B will automatically control how much the volume is turned up or down. Alternatively, the AGC can be manually controlled using the same procedures as GAIN described above. Refer to page 48 for further info.

Increases or decreases the overall amplitude of the signal. Much like turning

The PVX-B is equipped with an automatic gain control when operating in

PVX-B Precision Visual Thickness Gauge

Measure Mode: Used to select the measurement mode for different application requirements. The modes are P-E (pulse-echo), P-E GT(pulse-echo w/gate), and EE(echo-echo). Note: I-E or Interface echo mode is also a multiple echo mode that uses two gates like E-E mode(echo-echo). Refer to page 21 for further info.

3.3 CAL – Menu

Units:

readout will change from inches to millimeters (IN, IN HR, MM, MM HR). The high resolution options are indicated with HR following the units, and offer an additional decimal place of overall resolution (i.e. IN = .001” and IN HR = .0001”).

Velocity: Function to calibrate the PVX-B by setting the velocity to a known material velocity. Refer to page 31 for further info.

One Point: Performs a single point calibration. This option allows the user to automatically calculate the velocity by entering a known sample thickness. Refer to page 33 for further info.

Two Point: Performs a two-point calibration. This option allows the user to automatically calculate the velocity by entering a second known sample thickness. Refer to page 34 for further info.

Material: Select the material velocity from a chart of basic material types, when a known sample thickness or material velocity cannot be obtained. Refer to page 37 for further info.

Toggle between English or Metric units and low and hi resolutions. The

3.4 DISP (display) – Menu

View:

page 39 for further info. Backlight: Selectable OFF, ON, AUTO, or INVERT backlight option. The INVERT

option is actually a screen inversion that toggles background and foreground colors.

Contrast: B-ST:

Refer to page 41 for further info.

Selectable BSCAN (cross section), and DIGITS (large digits) views. Refer to

Adjustable display contrast for variable light conditions.

Provides the user the ability to change the start position of the B-SCAN view.

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B-DEP: Provides the user the ability to change the overall depth of the viewable measurement area. It functions a lot like a zoom on a camera. Refer to page 41 for further info.

3.5 SETUP – Menu

Open: These setups can be recalled and used at any time. Refer to page 74 for further info.

Save:

modified or created by the user. Refer to page 76 for further info. Default Setup: Loads a basic default setup. Use only as a last resort when the

setups in the PVX-B have been corrupted and a computer is not accessible. Refer to page 79 for further info.

Language: Provides the user with three different language options: English, German, and Spanish. Refer to page 52 for further info.

Displays a list of factory and user defined setups currently stored in memory.

Provides the user with the ability to save a custom setup that has been

3.6 DATA – Menu

Allows the user the ability to create a new alpha numeric grid with custom

New:

parameters, rows, and columns depending on their application reporting requirements. Refer to page 57 for further info.

Edit: Gives the user the ability to change parameters of grid that have been previously saved. Note: Pre-defined coordinates cannot be changed once they have been created. Refer to page 69 for further info.

Open:

exist in memory from a list of grids. Refer to page 71 for further info.

Delete One File:

individual grid from a list of multiple grids previously saved in memory. Refer to page 67 for further info.

Delete All Files:

currently stored in memory. Refer to page 67 for further info.

This function provides the user with the ability to recall grids that currently

This function provides the user with the ability to delete one

This function provides the user with the ability to delete all grids

PVX-B Precision Visual Thickness Gauge

3.7 UTIL (utilities) – Menu

Scan Mode:

overall sample rate from the standard 4 measurements a second to 32 measurements a second. Refer to page 52 for further info.

Alarm Status: Toggles alarm mode on or off. Refer to page 54 for further info. Alarm LO Limit:

measurement falls below this value, a red light will illuminate and sound the internal beeper. Refer to page 55 for further info.

Alarm HI Limit:

measurement exceeds this value, a red light will illuminate and sound the internal beeper. Refer to page 56 for further info.

This function enables a high speed scan mode that increases the

Gives the user the ability to set the LO limit parameter. If the

Gives the user the ability to set the HI limit parameter. If the

3.8 XFER (transfer) – Menu

Backup Setups: Enables the user the ability to backup the setups currently stored

in the PVX-B to a PC via RS232 port. Refer the help section of the DakView software for a complete electronic manual.

Restore Setups: Enables the user the ability to restore the setups currently saved on a PC to an PVX-B via RS232 port. Refer the help section of the DakView software for a complete electronic manual.

Backup File: Enables the user the ability to backup grids currently stored in the PVX-B to a PC via RS232 port. Refer the help section of the DakView software for a complete electronic manual.

Restore File:

an PVX-B via RS232 port. Refer the help section of the DakView software for a complete electronic manual.

About:

B software version. Refer the help section of the DakView software for a complete electronic manual.

Provides the user with Dakota Ultrasonics contact information and the PVX-

Enables the user the ability to restore grids currently saved on a PC to

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3.9 CLR (clear) Key

The primary functions of the CLR key, is to clear a measurement from a grid cell location or set obstruct, and backspace in an Alpha Edit Box. If a user has already saved a measurement and waveform to a cell location, use this key to clear the measurement at any time.

3.10 MEAS (measurement mode) Key

The MEAS key puts the PVX-B into it’s primary mode of operation. In this mode, the user has a complete view of the LCD, as well as control of the Hot Menu Functions. These hot functions provide the user with the ability to make crucial adjustments to the display, waveform settings, and grid storage locations without having to search through the menu and sub menu items. It’s important to first get familiar with moving around in the hot functions as follows:

Getting Around in the Hot Menus

1) Press the MEAS key at any time to return to the primarily measurement mode.

2) Press the MEAS key multiple times to tab right through the menu fields, and the ESC key multiple times to tab left through the menu fields, until the desired hot function is highlighted.

Now that you’re familiar with activating and moving amongst the hot function fields, let’s have a look at how to adjust or change the values of these fields:

Adjusting the Values of the Hot Menus

PVX-B Precision Visual Thickness Gauge

1) Use the UP, DOWN, LEFT, and RIGHT arrow keys to increase and decrease the values of the hot function fields.

2) Repeat step 1 until the desired value has been achieved.

Alternatively, the B-ST and B-DEP hot function fields can be changed using the Digit Edit Box as follows:

1) Press the ENTER key to display the Digits Edit Box.

2) Press the UP and DOWN arrow keys to scroll the highlighted value.

3) Press the LEFT and RIGHT arrow keys to scroll the digit locations.

4) Repeat steps 2 & 3 to adjust the other hot menu values.

5) Press the OK key to set and return to the measure screen, or ESC to cancel entering the B-ST or B-DEP values.

3.11 OK Key

The primary function of the OK key is confirmation of a change or selection. It also toggles the view from B-SCAN to DIGITS in previously saved grid location.

3.12 ESC Key

The ESC key is used in the MENU, MEAS, and EDIT functions as a back or escape function. It also toggles the view from B-SCAN to DIGITS in previously saved grid location.

3.13 Arrow Keys

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The Arrow Keys are used to navigate through the menus, increase/decrease values, and toggle specific function keys.

3.14 ENTER key

The ENTER key is used in the overall menu selection process, to activate list and edit boxes, and save measurements to grid locations.

3.15 MULTI MODE Key

The MULTI MODE key activates the Load Setup List to select a factory or previously saved user setup for a variety of different transducer types and settings. This is a quick automatic preset mode that enables the user to change modes and basic settings from the tabbed menus. The factory setups serve as the perfect starting point for immediate use or further fine-tuning.

3.16 ON/OFF Key

The ON/OFF key simply powers the unit either ON or OFF. Note: Unit will automatically power off when idle for 5 minutes. All current settings are saved prior to powering off.

3.17 Top & Bottom End Caps

The top & bottom end panels are where all connections are made to the PVX-B. The diagram above shows the layout and description of the connectors:

PVX-B Precision Visual Thickness Gauge

Transducer Connectors

Refer to Diagram: The transducer connector and battery cover/probe zero disk are located on the PVX-B’s top end cap. The transducer connector is of type Lemo “00”.

Probe Zero Disk & Battery Cover Refer to Diagram: The Battery cover is the large round disk shown in the diagram.

Note: This same disk is also used as a probe zero disk. Simply remove the cover

when replacing the batteries (3 AA cells). When performing a probe zero function, place the transducer on the disk making firm contact.

Important: Be sure to follow the polarity labels located on the back label of the PVXB. Note: Rechargeable batteries can be used, however they must be recharged

outside of the unit in a stand alone battery charger.

RS-232 Connector Refer to Diagram: The RS-232 connector, located on the bottom end cap, is a 2 pin

female Lemo connector. It is designed to connect directly from the PVX-B to a standard AT serial port on a PC. The cable supplied with the PVX-B is a Lemo to 9 pin serial cable. Note: This connector is also used to upgrade the PVX-B with the latest version of firmware.

CHAPTER FOUR PRINCIPALS OF ULTRASONIC MEASUREMENT

4.1 Time versus thickness relationship

Ultrasonic thickness measurements depend on measuring the length of time it takes for sound to travel through the material being tested. The ratio of the thickness versus the time is known as the sound velocity. In order to make accurate measurements, a sound velocity must be determined and entered into the instrument.

The accuracy of a thickness measurement therefore depends on having a consistent sound velocity. Some materials are not as consistent as others and accuracy will be marginal. For example, some cast materials are very granular and porous and as a result have inconsistent sound velocities.

While there are many different ultrasonic techniques to measure thickness, which will be discussed below, all of them rely on using the sound velocity to convert from time to thickness.

4.2 Suitability of materials

Ultrasonic thickness measurements rely on passing a sound wave through the material being measured. Not all materials are good at transmitting sound. Ultrasonic thickness measurement is practical in a wide variety of materials including metals, plastics, and glass. Materials that are difficult include some cast materials, concrete, wood, fiberglass, and some rubber.

4.3 Range of measurement and accuracy

The overall measurement capabilities, based on the wide variety of materials, is determined by the consistency of the material being measured

The range of thickness that can be measured ultrasonically depends on the material as well as the technique being used and the type of transducer. Thickness measurements can be made from a minimum of 0.010 inch to 9.999” in steel. However, the maximum attainable thickness is much less for more attenuative materials (materials that absorb sound).

Accuracy, is determined by how consistent the sound velocity is through the sound path being measured and, is a function of the overall thickness of the material. For example, the velocity in steel is typically within 0.5% while the velocity in cast iron can vary by 4%.

4.4 Couplant

All ultrasonic applications require some medium to couple the sound from the transducer to the test piece. Typically a high viscosity liquid is used as the medium. The sound frequencies used in ultrasonic thickness measurement do not travel

PVX-B Precision Visual Thickness Gauge

through air efficiently. By using a liquid couplant between the transducer and test piece the amount of ultrasound entering the test piece is much greater.

4.5 Temperature

Temperature has an effect on sound velocity. The higher the temperature, the slower sound travels in a material. High temperatures can also damage transducers and present a problem for various liquid couplants.

Since the sound velocity varies with temperature it is important to calibrate at the same temperature as the material being measured.

Normal temperature range

Most standard transducers will operate from 0F to 180F.

High temperature measurements

Special transducers and couplants are available for temperatures above 180F up to 650F with intermittent contact. It is necessary to cool the transducer, by submerging the transducer in water between readings, when measuring high temperatures.

Modes and temperature errors

In addition to errors caused by velocity changing with temperature, some modes (measurement techniques) are affected more than others. For example, dual element mode has larger errors due to changes in temperature of the delay line. However, multi-echo techniques help to minimize these errors. The PVX-B operates in multi-echo modes for a variety of transducer types.

4.6 Measurement Modes

In this section we will discuss the different measurements modes the PVX-B is capable of operating in, the transducers required, and the reasons for using specific modes:

Pulse-Echo Mode

Pulse-echo mode measures from the initial pulse (sometimes referred to as an artificial zero) to the first echo (reflection). In this mode, the transducer is placed on a reference disk, located on top of the PVX-B, and a key is pressed to establish a zero point for the particular transducer.

In pulse-echo mode errors result from surface coatings and temperature variations. This mode is only used with single element contact style transducers.

Echo-Echo (Interface-Echo) Modes

The echo-echo modes measure between two reflections. This technique is commonly used to eliminate errors from surface coatings in echo-echo mode, as well as make measurements in multiple layered materials. The disadvantage is that two

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echoes are needed which requires a much stronger echo (reflection). In interfaceecho mode, it moves the interface further out in time eliminating any noise that’s close to the initial pulse.

Important: The primary difference between interface-echo and echo-echo mode, is interface-echo mode measures from the end of an interface (delay line), to the first return reflection of the test material. However, in echo-mode, the measurement is made between two return reflections (echoes). Although both modes use two gates and virtually look the same on the scope, they are measuring in different ways and are used to accomplish different application tasks. The diagrams below will offer an additional explanation of the differences in these modes as follows:

Delay Line Single Element Transducer in Interface-Echo mode

Diagram 1

Refer to diagram 1. This diagram illustrates the sound path being measured in

interface-echo mode. (A) is the transducer. Point (B) is the piezoelectric crystal that emits the sound wave. (C) is the delay line, most commonly made of acrylic or graphite. The delay tip will act as the interface and the measurement will be made starting from the difference of the reflection off the end of the delay tip (E). The sound will also travel through the delay tip (C) and test material (F), and reflect back to the piezoelectric crystal off the back wall of the test material. The measurement will be made from the reflection off the end of the delay tip and back wall of the test material.

4.7 Glossary of terms

Repetition Rate & Display Update

The repetition rate is how often the PVX-B generates a burst of ultrasound. The PVX-B has a fixed repetition rate of 1 kHz, or 1000 times per second. The PVX-

B updates the display 4 times per second in regular measurement mode and 32 times a second in hi speed scan mode. Therefore, the scan mode is most suitable for fast scans of a test piece at a lower resolution.

CHAPTER FIVE SELECTING THE MEASUREMENT MODE

5.1 The setup library

The PVX-B contains 18 factory setups and 46 user definable preset locations to store custom setups for easy recall. These setups can be optimized for the user’s specific application needs and can also be stored on a PC and transferred bi-directionally using Dakota’s PC interface software included with the instrument.

The setups supplied with the instrument are optimized for specific transducer types and serve as a starting point for some of the typical applications commonly used with this type of instrument. These setups can be recalled, modified, and overwritten to one of 46 setup locations. The PC software includes a default setup file that can be uploaded to the gauge at any time to restore factory settings. Note: The first 18 setups cannot be overwritten. Once again, these factory settings are excellent starting points for custom setups.

5.2 Which mode & transducer do I use for my application?

High penetration plastics and castings

The most common mode for these types of applications is pulse-echo. Select a low frequency transducer. Depending on the thickness of the material, use a 2.25MHz or lower frequency transducer. Larger diameters offer greater penetration power because of the crystal size, for difficult to measure materials.

Thin Materials & Tough Access Areas

Use any of the delay-line transducers for materials under 1 inch. Tough access areas with minimal clearances, are perfect applications for our pencil style transducers. However, the pencil transducer have a very small thickness range and are only suitable for thin materials less than .300”.

Thru Paint & Coatings

Often time users will be faced with applications where the material will be coated with paint or some other type of epoxy material. Since the velocity of the coating is approximately 2.5 times slower than that of steel, pulse-echo mode will induce error if the coating or paint is not completely removed. By using echo-echo mode, the user is able to successfully measure through both, the coating and steel, and completely eliminate the thickness of the paint or coating. Therefore, the steel can be measured without having to remove the coating prior to measuring.

Both the delay-line and contact transducers will work fine for thru coating measurements. When using contact style transducers, it’s best to consider a high damped model for thinner materials to minimize the potential ring down noise of the transducer.

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Dakota Ultrasonics PVX-B Operating Manual

Specifications and Main Features

Frequently Asked Questions

User Manual