Dakota Ultrasonics DFX-8 Operating Manual

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OPERATION MANUAL

DAKOTA ULTRASONICS

DDFFXX--88 SSeerriieess

Material & Coating Thickness Gauges

(Manual 1 of 2)

P/N P-250-0003 Rev 1.2, June 2014

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

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

CHAPTER THREE KEYBOARD, MENU, & CONNECTOR REFERENCE ....... 25

CHAPTER FOUR PRINCIPALS OF ULTRASONIC MEASUREMENT ............ 40

CHAPTER FIVE SELECTING THE MEASUREMENT MODE .......................... 45

CHAPTER SIX MAKING MEASUREMENTS .................................................... 48

CHAPTER SEVEN USING THE DISPLAY OPTIONS ...................................... 63

CHAPTER EIGHT THRU PAINT MEASUREMENT TECHNIQUE ................... 94

CHAPTER NINE PULSE-ECHO COATING & COATING TECHNIQUES ........ 97

CHAPTER TEN ADDITIONAL FEATURES OF THE DFX-8 ........................... 112

CHAPTER ELEVEN DATA STORAGE – SETUP, EDIT, & VIEW FILES ....... 134

CHAPTER TWELVE SETUPS – CREATE, STORE, EDIT, & RECALL ......... 158

CHAPTER THIRTEEN SOFTWARE, FILE TRANSFER, & UPGRADES ....... 168

APPENDIX A - VELOCITY TABLE ................................................................. 174

APPENDIX B - SETUP LIBRARY ................................................................... 176

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CHAPTER ONE INTRODUCTION

The Dakota Ultrasonics model DFX-8 is both, an ultrasonic thickness gauge, as well as a flaw detector. Since the DFX-8 is basically two gauges in a single package, we

split the manual into two manuals, one for each gauge type. This manual will focus

only on the thickness gauge portion of the gauge. The DFX-8 has the ability to

simultaneously measure coatings and material thicknesses while maintaining the ability to locate pits, flaws and defects in the material. Based on the same operating

principles as SONAR, the DFX-8 is capable of measuring the thickness of various

materials with accuracy as high as  0.001 inches, or  0.01 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 General Disclaimer

The manual should be read and understood prior to using the DFX-8. This operating

manual provides the user with all the general information necessary to use and adjust the designed features. However, this manual is not a certified NDT training course, nor is it intended to be one. Training, according to company requirements, is recommended.

Inherent in ultrasonic thickness measurement is the possibility that the instrument will use the second rather than the first echo from the back surface of the material being measured. This may result in a thickness reading that is TWICE what it should be. Responsibility for proper use of the instrument and recognition of this phenomenon rest solely with the user of the instrument. Other errors may occur from measuring coated materials where the coating is insufficiently bonded to the material surface. Irregular and inaccurate readings may result. Again, the user is responsible for proper use and interpretation of the measurements acquired.

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CHAPTER TWO QUICK STARTUP GUIDE

Turn the DFX-8 on and off using the switch located on the bottom right corner of the keypad. When DFX-8 is initially turned on, a flash logo and blinking lights will be

displayed, followed by attempting to identify the transducer (probe) currently plugged

into the gauge. The DFX-8 is equipped with an “Auto Probe Recognition” feature that attempts to identify special transducers with this built in feature. If the DFX-8 doesn’t

find a transducer equipped with this feature, the user will be advanced to a list of transducers requiring the user to select a specific transducer type. The following sections outline each scenario. Note: This section is primarily written as a basic startup guide only.

2.1 DFX-8 Overview

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In order to understand how to operate the DFX-8, it’s best to start off with an understanding of what it is we’re looking at exactly. The DFX-8 has a lot of great

features and tools that will prove to be a huge benefit for the variety of applications you’re constantly facing on a continual basis. Let’s have a brief look at the screens you’ll be looking at most often:

A. Repeatability/Stability Indicator – This indicator should be commonly used

in conjunction with the digital thickness values displayed. When all the vertical bars are fully illuminated and the last digit on the digital thickness value is

stable, the DFX-8 is reliably measuring the same value 3 to 200 times per

second, depending on which measurement mode and features are enabled.

B. Battery Icon – Indicates the amount of battery life the DFX-8 has remaining. C. Velocity – The material velocity value the DFX-8 is currently using or

calibrated for. Displayed in both English or Metric units, depending on the what units the gauge is set for.

D. Feature Status Bar – Indicates the features currently enabled and in use in

the following order:

 Measurement Mode

 Differential Mode

 High Speed Scan Mode

 Alarm Mode

 Gain Setting

E. Digital Material Thickness Values – Depending on the measurement mode

selected, the base material and coating thicknesses are displayed. If the scan feature is enabled, the minimum and maximum thickness value of the base material is displayed and updated simultaneously during the scan .

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F. Scan Bar – Another view of material thickness in a deflection style horizontal

bar. This is a visual tool that would enable the user the ability to see thickness

changes during high speed scans from flaws and pits. G. Units – The current measurement units being used (English, Metric). H. Hot Menu items – We call this menu section our “hot menu”, as these items

are the most commonly adjusted features, requiring quick access from the

user. They can be displayed and scrolled by pressing the MEAS key at any

time. The MEAS key advances forward and the ESC key backwards to the

next hot menu item. Alternatively, the UP,DOWN, LEFT and RIGHT arrow

keys on the left button wheel can be used to either scroll through the sub

menu items, or advance to the next HOT MENU items list. There are 8 HOT

MENU lists, that contain the most commonly adjusted items from the tabbed

menus, and in the same order as the tabbed menus. Note: Some of the lists

contain multiple tabbed menus in order to condense the number of HOT

MENU lists. I. B-Scan Display – Cross section view of the material. Provides the user with

graphical view of the opposite/blind surface (i.e. inside pipe wall surface), to

give the user some idea of the condition, or integrity of the material being

tested. J. Gain & Step Size – The gain and increment step size can be continuously

used and adjusted at any time using the UP and DOWN arrow keys on the

right button wheel to scroll the value, and the GAIN key to activate the Digit

Edit screen to adjust the step size. K. Rectified A-Scan Display – The actual sound wave reflection that is returned

from the detection of the opposite surface of the material being measured. In

this view, only half of the sine wave is being displayed (positive or negative).

This view is commonly referred and used as a “flaw detection” mode. L. Reference Note – When a full screen sound wave is being displayed, the

material thickness value is displayed here. M. Reference Note – In a split screen mode the material velocity is displayed

here. N. Split Screen Display – This display option ‘splits’ the screen in half,

displaying the waveform/B-Scan and the thickness values concurrently.

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2.2 Gauge Type

Power up the DFX-8, by pressing the on/off key located in the bottom right corner of

the keypad. During initial boot up, a flash screen and lights will be displayed, followed by a GAUGE TYPE selection screen. Since this manual will focus on the

thickness gauge portion of the DFX-8, use the UP/DOWN arrow keys to select “thickness gauge”, followed by pressing the OK key start the DFX-8 in thickness

mode.

2.3 Top & Submenu Reference

The following table is a quick menu reference guide. The DFX-8 has 15 top level menu titles, and multiple submenu items as illustrated below. The DFX-8 also has 8

‘hot menu’ subsets of the same menu structure. These are the most commonly adjusted submenu items from each of the top level menus. They can be quickly

accessed from the main measurement screen by pressing the LEFT and RIGHT

arrow keys multiple times using the left button wheel, and pressing the UP and DOWN arrow keys on the left button wheel to select the appropriate submenu item. Refer to Chapter Three for additional definitions and information on the keypad and menu items.

1st Main Hot Menu

Additional Hot Menus

Note: “Log” is also listed in the 1st main Hot Menu, and is used to access data storage if no log file is currently open, or display log or grid file if open.

Start >>

PRB CAL DISP TUNE GT1 GT2 GT3 SETUP

ZERO PROBE MAT VIEW MEASURE

MODE

ZERO MATL 1PT DELAY POLARITY GATE1 WIDTH HOLDOFF 2 HOLDOFF 3 SAVE

START GATE2 WIDTH GATE3 WIDTH OPEN

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COATING

TYPE MATL 2PT RANGE PULSE THRESHOLD 1 THRESHOLD 2 THRESHOLD 3 DELETE

VELOCITY B-SCAN

SPEED

COATING 1PT UNITS DAMPING

COATING 2PT BRIGHTNESS GAIN LANGUAGE

COATING VEL COLORS AGC

DIM

RECT WAVE

DETECT MARK

PULSER

VOLTAGE

DEFAULT

SETUP

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>> End

DATA UTILS XFER

NEW AUTO FIND BACKUP

SETUPS

EDIT SCAN MODE COPY DATA

OPEN ALARM COPY

SCREENS

CLOSE ALARM HIGH UPGRADE

GAUGE

DFX-8 Ultrasonic Thickness Gauge

DELETE ONE

FILE

DELETE ALL

DATA

GAUGE ABOUT

ALARM LOW CAPTURE TO

FILE

DIFFERENTIAL STORAGE

2.4 Auto Probe Recognition

When the DFX-8 is initially powered up, the gauge will automatically check to see if

the transducer plugged into the gauge can be recognized. The steps that follow

assume the DFX-8 recognized the probe type:

Probe Automatically Recognized

1) Press the OK key once to use the identified probe, or ESC to display a list of

optional transducers. Note: if the DFX-8 recognizes a specific transducer,

the user should always select OK to use the identified probe. The only time

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an alternative probe should be selected from a list is if the user switched probes following initial power up and recognition.

2) Assuming the DFX-8 recognized the probe and the OK key was pressed, the DFX-8 will advance to a Zero Probe menu. If the transducer was

identified as a special transducer capable of measuring coating thickness, a

menu will be displayed allowing the user the ability to toggle the coating

thickness display on/off as follows:

3) Press the UP and DOWN arrow keys on the left button wheel to toggle

the coating option on/off.

4) Wipe all couplant from the transducer face and advance to the Probe Zero

& Calibration section outlined below.

2.5 Selecting the Transducer Type

If the DFX-8 does not identify a specific transducer type on initial power up, the user

will be required to select a type from a predefined list of types by diameter and

frequency. By selecting a transducer type from a predefined list, the DFX-8 can

recall specific properties about the transducer. Note: Once the transducer has been

selected, the DFX-8 will store and recall this transducer type every time the DFX-8 is

powered on/off. The type will only change if the user physically selects another

transducer type from the list, or selects a previously saved setup. However, the DFX- 8 will continue to take you through these steps each time the gauge is powered up.

You’ll notice that the probe type previously selected will be highlighted every time the probe type screen is displayed. Use the following steps to select your transducer type:

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Selecting the Transducer Type

1) Press the OK or ESC keys to display the factory list of transducer types (by

diameter and frequency).

2) Press the UP and DOWN arrow keys on the left button wheel to scroll

through the transducer list until the appropriate type is highlighted.

3) Press the ENTER key to select the transducer type and display overwrite

existing probe screen.

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4) Press the OK key to overwrite the existing probe type with the newly

selected probe type. The zero probe screen will be displayed. Proceed to

the zero probe section that follows.

2.6 Probe Zero & Calibration

The next steps are to perform a probe zero and calibrate the DFX-8 to the material and transducer being used. If the sound velocity is unknown, the DFX-8 can be

calibrated to a known thickness sample. This demo will briefly explain both of these techniques.

The DFX-8 is equipped with two zero options:

1) Off Block Zero (Automatic Probe Zero) – When this feature is enabled the

DFX-8 will do an electronic zero automatically, eliminating the need for a zero

disk or block.

2) On Block Zero (Manual Probe Zero) – When this feature is enabled the transducer must be placed on the probe zero disk (battery cover located on the top of the unit.

Note: Transducers of the same type will have very slight mechanical and electrical variations. If it’s discovered that the linearity is off following an initial auto probe zero and extreme accuracy is required, a manual zero should be performed followed by an auto zero. This will adjust and eliminate any error. This is only required if it’s discovered the transducer is non-linear following an initial auto probe zero.

The procedures are outlined as follows:

Performing an Auto Probe Zero (Off Block)

Coating Probe Identified Coating Probe Not Identified

1) Be sure all couplant has been removed from the face of the transducer.

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2) Press the OK key to perform the automatic probe zero, or ESC key to

cancel the zero operation.

3) The screens illustrated above will be briefly displayed followed by the main

measurement screen. The DFX-8 is ready to be calibrated.

Performing a Manual Probe Zero (On Block)

Note: When the zero probe option is set to manual, the probe zero disk

(battery cap) located on the top of the gauge, will be used as a zero standard

and the warning screen illustrated above will be displayed.

1) Press the OK or ESC keys to enter the main measurement screen and

begin the manual zero process.

2) Apply a drop of couplant on the transducer and place the transducer in

steady contact with the probe zero disk, and obtain a steady reading.

3) 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 PRB menu is highlighted and displaying the submenu items.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel to scroll the tabbed menus.

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4) Press the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until ZERO PROBE is highlighted.

Coating Probe Identified Coating Probe Not Identified

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

6) If a coating transducer was identified use the UP and DOWN arrow

keys on the left button wheel to toggle coating on/off.

7) Press the OK key to complete the probe zero function, or ESC key to cancel

the probe zero function.

8) Remove the transducer from the probe zero disk, and proceed to the

calibration section.

Note: The value that is displayed will change depending on the current velocity

setting in the DFX-8. Disregard the number that is displayed. It is not

important. What is important is accurately performing the steps outlined above

to insure reliability of the probe zero calculation.

One Point Material Calibration

For the purposes of this quick start section, we’ll only be covering the most common one point calibration option to determine the sound velocity of the test material. It would be very handy to carry a set of mechanical calipers to use in conjunction with

the DFX-8 for calibration in the field:

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Using a Known Thickness

Note: Be sure that the probe zero procedure has been performed prior to

performing this calibration procedure.

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. Alternatively, press the LEFT and

RIGHT arrow keys multiple times using the left button wheel.

3) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until MATL 1PT is highlighted.

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

5) Press the UP and DOWN arrow keys on the left button wheel to scroll

the highlighted value.

6) Press the LEFT and RIGHT arrow keys on the left button wheel to scroll

the digit locations.

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

8) Press the OK key to calculate the velocity and return to the menu screen, or

ESC to cancel the one point calibration.

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.

2.7 Zero Coating

In order to account for very slight electronic differences in transducers of the same

type, frequency, and diameter, the DFX-8 has been equipped with a “zero coating” feature. This enables the DFX-8 to obtain very accurate readings on coatings,

eliminating potential errors incurred from slight differences in the manufacturing processes. The procedure is outlined below:

Performing a Coating Zero

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1) Press the MULTI MODE key once to activate the measurement mode

options.

2) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until Coating Only (CT) mode is highlighted.

3) Press the MEAS key to select the measurement mode and return to the

measurement screen.

4) Apply a drop of couplant on the transducer and place the transducer in

steady contact with one of the probe zero disks (emergency battery covers)

and obtain a steady reading.

Note: The coating measurement displayed will potentially be a value greater or

less than 0.

5) 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 PRB menu is highlighted and displaying the submenu items.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel.

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6) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until ZERO COATING is highlighted.

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

8) Press the OK key to zero the coating and return to the PRB menu, or ESC

to cancel the coating zero process.

9) Press the MULTI MODE key once to activate the measurement mode

options.

10) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until Coating On (PECT) is highlighted.

11) Press the ENTER key to select the measurement mode and return to the

measurement screen, and begin taking readings.

2.8 Coating Calibration

The DFX-8 has been preset to a default coating velocity of 0.0850 in/µsec (2159

m/sec). This will be very close to the most common coating material velocities used in the field. If the velocity of the coating is known, and different than the above

default setting, the user can simply enter the coating velocity into the DFX-8. However, if the velocity is unknown, the DFX-8 can also be calibrated to a specific

coating sample/type using the 1pt calibration option in PECT (pulse-echo coating) mode, or a two point calibration is CT (coating only) mode. For the purpose of this quick start section only the 1pt option PECT (pulse-echo coating) mode will be covered. Refer to the calibration section of the manual for a complete explanation on the coating calibration options. The following steps below outline the necessary steps to either set the velocity of the coating, or perform a one point calibration to calculate the coating velocity:

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Known Coating Velocity

If the coating velocity is known, the user may wish to simply enter the velocity

number into the DFX-8, rather than have the DFX-8 calculate the velocity value using

a known thickness on a coating sample. The steps for entering the velocity are outlined below:

Using a Known Coating 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.

2) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until COATING VEL 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 on the left button wheel 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 coating velocity and return to the menu screen,

or ESC to cancel entering the coating velocity.

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8) Finally, press the MEAS key to return to the measurement screen and

begin taking readings.

Known Coating Thickness

When the exact velocity of a coating is unknown, the user has the option of performing a one point calibration on a sample of the coating with a known thickness to determine the sound velocity. It would be very handy to carry a set of mechanical

calipers to use in conjunction with the DFX-8 for calibration in the field:

Using a Coating Sample to Calibrate

1) Physically measure a location on a coating sample using a set of calipers or

a digital micrometer.

Important Note: In PECT (pulse-echo coating) mode, the coating sample must

be coupled to metal in order to calibrate successfully. Simply place a drop of

couplant on a piece of metal, lay the coating sample over the couplant on the

metal and proceed to step 2.

2) Apply a drop of couplant on the transducer and place the transducer in

steady contact with the coating (on metal) sample or actual test material. Be

sure that the reading is stable and the repeatability indicator, in the top left

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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. Alternatively, press the LEFT and

RIGHT arrow keys multiple times using the left button wheel.

3) Use the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until COATING 1PT is highlighted.

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

5) Press the UP and DOWN arrow keys on the left button wheel to scroll

the highlighted value.

6) Press the LEFT and RIGHT arrow keys on the left button wheel to scroll

the digit locations.

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

8) Press the OK key to calculate the coating velocity and return to the menu

screen, or ESC to cancel the one point calibration.

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 coating thickness reading should now match the known

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coating thickness sample. If the thickness is not correct, repeat the steps

above.

2.9 Measure

The DFX-8 is now ready to measure. There are four different measurement view

options, each with a specific purpose – Digits, RF, RECT, & B-Scan. 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.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel.

2) Use the UP and DOWN arrow keys on the left button wheel to scroll the

sub menu items until VIEW is highlighted.

3) Use the LEFT and RIGHT arrow keys on the right button wheel to scroll

the view options.

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

mode.

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DIGITS: Displays the digital thickness value using a large font size. This view is

useful when the DFX-8 is being used as a basic thickness gauge.

RF: Displays the actual waveform signal, much like an oscilloscope, from the reflection of the opposite surface, pit, flaw, crack or void. This view shows both the positive and negative peaks, and is often used to fine tune the scope settings, prior to inspection.

RECT: Displays a half waveform signal, either positive or negative, from the reflection of the opposite surface, pit, flaw, crack or void. The user can select the polarity or “phase” displayed. This is typically determined by first using RF view to select the most optimal polarity “phase”, to fine tune the scopes settings. The RECT view is commonly used as the primary “flaw detection” view.

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. This can also be a useful view when scanning for pits and flaws.

Once the view has been selected according to the application requirements, the Delay and Range of the screen will potentially need to be adjusted, if the view has been set to RF or RECT. Alternatively, if BSCAN was selected, the B-Start and B- Depth settings will need to be adjusted. These settings serve the same purpose, with only differences in terminology. The Delay the same as B-Start, and the Range is the same as B-Depth. Therefore, these items will be grouped together for the duration of this manual, as follows: Delay (B-Start) and Range (B-Depth). Use the following steps to adjust these settings directly from the measurement screen as follows:

Note: The Delay (B-Start) and Range (B-Depth) are also used to adjust the parameters of Scan Bar.

Adjusting Delay (B-Start) & Range (B-DEPTH)

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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 DELAY (START) or RANGE (DEPTH) cell is

highlighted. Alternatively, use the UP and DOWN arrow keys on the left

button wheel.

2) Use the LEFT and RIGHT arrow keys on the right button wheel to scroll

the DELAY (START) and RANGE (DEPTH) values.

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

Alternatively, the DELAY (START) and RANGE (DEPTH) values can be

changed using the Digit Edit Box as follows:

4) 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 DELAY (START) or RANGE (DEPTH) cell is

highlighted. Alternatively, use the UP and DOWN arrow keys on the left

button wheel.

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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 UP and DOWN arrow keys on the left button wheel to scroll

the digit locations.

4) Repeat steps 2 & 3 until the DELAY (START) or RANGE (DEPTH) value is

correctly displayed.

5) Press the OK key to set the DELAY (START) and WIDTH (DEPTH) value

and return to the measure screen, or ESC to cancel entering the DELAY

(START) or WIDTH (DEPTH) value.

6) Finally, press the MEAS key to return to the measurement screen and begin

taking readings.

Note: The DELAY (START) & WIDTH (DEPTH) can also be adjusted from the

tabbed menu item DISP. However, using the hot menu keys is the easiest

method.

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RF View Rectified (RECT) View

In the upper left corner of each of the display 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 DFX-8 makes 8 measurements a second. In scan mode, the DFX-8 makes 200 measurements a second. If the coating mode option is activated, the DFX-8 makes 3

measurements a second in regular measurement mode and 65 measurements a

second in scan mode. When the DFX-8 is idle, only the left vertical bar will be displayed. However, when the DFX-8 is making a measurement, four or five of the

bars should be displayed on the repeatability indicator. If fewer than four bars are

showing, the DFX-8 is having difficulty achieving a stable measurement and the

thickness value displayed is potentially unstable.

Digits View B-Scan View

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CHAPTER THREE KEYBOARD, MENU, & CONNECTOR REFERENCE

3.1 Menu Key (Operation & Sub Menus)

The Menu key activates the primary menu structure containing 10 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:

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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.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel. The tab groups are illustrated above (A).

Now that you’re 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 on the left button wheel to scroll

through the sub menu items until the desired function is highlighted. The

sub menu items are illustrated in the diagram above (B).

2) Depending on which function is highlighted, use the LEFT and RIGHT

arrow keys on the right button wheel to scroll the options, or the ENTER key

to activate the Digit Edit and List Box options.

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

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3.2 Probe – Menu

ZERO PROBE:

micrometer is zeroed. If the DFX-8 is not zeroed correctly, all of the measurements

made using the DFX-8 may be in error by some fixed value. The DFX-8 is equipped

with an optional automatic or manual zero feature. Refer to the section on page 51, for an explanation of this important procedure.

ZERO COATING: In order to account for very slight electronic differences in

transducers of the same type, frequency, and diameter, the DFX-8 has been equipped with a “zero coating” feature. This enables the DFX-8 to obtain very

accurate readings on coatings, eliminating potential errors incurred from slight differences in the manufacturing processes. Refer to the section on page 51, for a detailed explanation.

TYPE:

transducer types. This provides increased linearity between transducers. Refer to page 48 for a further explanation.

Enables the user to select the type of transducer being used from a chart of

The DFX-8 is zeroed in much the same way that a mechanical

3.3 CAL – Menu

MAT: 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 60 for further info.

MATL 1PT:

automatically calculate the velocity by entering a known sample thickness. Refer to page 57 for further info.

MATL 2PT: 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 59 for further info.

VELOCITY:

material velocity. Refer to page 55 for further info.

Performs a single point calibration. This option allows the user to

Function to calibrate the DFX-8 by setting the velocity to a known

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COATING 1PT: Performs a single point coating calibration. This option allows the user to automatically calculate the velocity by measuring a known coating sample thickness. Refer to page 107 for further info.

COATING 2PT: Performs a two-point coating calibration. This option allows the user to automatically calculate the velocity by entering a second known coating sample thickness. Refer to page 107 for further info.

COATING VEL: Function to calibrate the DFX-8 to a specific coating material type

by entering a coating velocity. Refer to page 17 or page 101 for further info.

3.4 DISP (display) – Menu

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

page 64 for further info. DELAY (B-START): Provides the user the ability to change the start position of the

B-SCAN view. Refer to page 72 for further info. RANGE (B-DEPTH): 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 74 for further info.

B-SCAN SPEED: Controls the speed of the time based B-Scan with an arbitrary

scale of 0-10, with 10 being the fastest scrolling speed. Default speed set at 6. Refer to page 76 for further info.

UNITS: Toggle between English or Metric units. The readout will change from inches to millimeters.

BRIGHTNESS:

been implemented, with the brightest setting at 20. Refer to page 118 for further info. COLOR: Provides the user with 12 different color schemes to select from. There are

two schemes for each main color option. Refer to page 119 for further info.

DIM: Allows the user to conserve battery life by diming the display after idle for a

specific amount of time – OFF, 30, 60, 90, 120 seconds. Once dimmed, a single press of any key will restore the screen brightness. Refer to page 121 for further info.

RECT WAVE:

the display setting is in RECT (rectified) wave mode only. Refer to page 123 for further info.

DETECT MARK: Selectable graphics option for the point of detection on the waveform: Line, Box, Dots, None. Offers the user a graphics preference on how they prefer to view the detection on the waveform.

Blanview high speed color display. An arbitrary scale of 1-20 has

This option provides the user an outlined or filled view option when

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3.5 TUNE – Menu

MEASURE MODE: Toggles a variety of unique measurement modes for different

application requirements: Coating Off (P-E), Coating On (PECT), Temp Comp (PETP), Thru Coat (E-E), Thru Verify (E-EV), Coating Only (CT). Refer to page 41 for further info.

POLARITY: The DFX-8 operates on a zero crossing detection principle. This

feature toggles which stroke of the cycle the crossing detection uses, either positive or negative. Refer to page 125 for further info.

PULSE: The DFX-8 has an adjustable pulse width for both high penetration and

resolution applications. The pulse width refers to the duration of time the pulser is on. The options are Spike, Thin, and Wide. Refer to page 127 for a further explanation.

PULSER VOLTAGE: This feature offers a 50 volt cut/boost to the pulser. The

standard setting is 150 volts. This enables the DFX-8 to offer greater penetration for

difficult material types, or increased resolution on noisy materials. Refer to page 128 for a further explanation.

DAMPING: Provides the user with multiple input impedances to match the

impedance of the transducer, and optimized overall transducer performance. Refer to page 122 for further info.

GAIN:

with the attenuator feature above. This feature is used to increase/decrease the power or amplitude of the signal. This might easily be considered as similar to turning the volume up or down on a stereo receiver. Refer to page 77 for further info.

AGC:

verify). The DFX-8 is equipped with an automatic gain control when operating in -E

(echo-echo), and E-EV (echo-echo verify) modes only. This feature automatically increases/decreases the power or amplitude of the signal, to an optimal input to output signal ratio. This might easily be considered as similar to turning the volume up or down on a stereo receiver. Alternatively, the AGC can be manually controlled.

The DFX-8 is equipped with manual override, using an arbitrary range of 1-20 clicks.

The higher the number the better the dynamic gain range, and visa versa. Refer to page 77 for further info.

The DFX-8 has 100dB gain range from (-30 to 70 dB), used in conjunction

This an automatic gain control used in E-E (echo-echo), and E-EV (echo-echo

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3.6 GT1 – Menu

GATE1: Gates allow the user to view a specific measurement range, or sections of

the waveform, and ignore others. The Gate1 feature adjusts the start of the gate, according to time/distance. Gate 1 can be used in all pulse-echo and echo-echo measurement modes. Refer to page 85 for further info.

GATE1 WIDTH: This feature allows the user to set the overall width of the gate, in terms of distance, from the starting value of Gate1. Refer to page 85 for further info.

THRESHOLD1: Enables the user to set the sensitivity level of Gate1. The amplitude of the signal must reach or exceed the threshold level before a measurement is detected. Refer to page 85 for further info.

3.7 GT2 – Menu

GATE2 WIDTH: This feature allows the user to set the overall width of the gate, in

terms of distance, from the starting value of HoldOff2. Refer to page 85 for further info.

HOLDOFF 2: Provides the user with the ability to delay the starting point of Gate2, a specific distance from the first detection point found inside of the boundaries of the Gate 1 settings. If no detection is found, the Gate1 width value is used as a starting value for Gate2. Refer to page 85 for further info.

THRESHOLD2:

of the signal must reach or exceed the threshold level before a measurement is detected. Refer to page 85 for further info.

Enables the user to set the sensitivity level of Gate2. The amplitude

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3.8 GT3 – Menu

GATE3 WIDTH: This feature allows the user to set the overall width of the gate, in

terms of distance, from the starting value of HoldOff3. Refer to page 85 for further info.

HOLDOFF 3: Provides the user with the ability to delay the starting point of Gate3, a specific distance from the first detection point found inside of the boundaries of the Gate 2 settings. If no detection is found, the Gate2 width value is used as a starting value for Gate3. Refer to page 85 for further info.

THRESHOLD3: Enables the user to set the sensitivity level of Gate3. The amplitude of the signal must reach or exceed the threshold level before a measurement is detected. Refer to page 85 for further info.

3.9 SETUP – Menu

OPEN:

These setups can be recalled and used at any time. Refer to page 158 for further info.

SAVE:

modified or created by the user. Refer to page 160 for further info.

DELETE:

in memory. Refer to page 163 for further info.

DEFAULT SETUP:

setups in the DFX-8 have been corrupted and a computer is not accessible. Refer to

page 165 for further info.

LANGUAGE:

8. Refer to page 167 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

Provides the user with the ability to delete specific setups previously save

Loads a basic default setup. Use only as a last resort when the

Provides the user the ability to select different languages for the DFX-

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3.10 DATA – Menu

NEW: Allows the user the ability to create a new alpha numeric grid, or sequential

log file with auto identifiers. It is equipped with custom parameters, rows, and columns depending on the user’s application reporting requirements. Refer to page 135 for further info.

EDIT: Gives the user the ability to change parameters of grid or sequential file previously saved. Note: Pre-defined coordinates cannot be changed once they have been created. Refer to page 152 for further info.

OPEN: This function provides the user with the ability to recall grids or sequential log files that currently exist in memory, from a list of grids. Refer to page 154 for further info.

CLOSE: Provides the user the ability to close a currently opened grid or sequential log file. Refer to page 156 for further info.

DELETE ONE FILE: This function provides the user with the ability to delete one individual grid or sequential log file from a list of multiple grids/files previously saved in memory. Refer to page 149 for further info.

DELETE ALL DATA: This function provides the user with the ability to delete all files currently stored in memory. Refer to page 150 for further info.

3.11 UTIL (utilities) – Menu

AUTO FIND: the viewable display area. Refer to page 112 for further info.

SCAN MODE:

overall sample rate from 65 to 200 measurements per second, depending on the current measurement mode used. Refer to page 112 for further info.

ALARM:

Automatically locates the detection point if the measurement is out of

This function enables a hi speed scan mode that increases the

Toggles alarm mode on, off, or audible. Refer to page 114 for further info.

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ALARM HIGH: Gives the user the ability to set the HI limit parameter. If the measurement exceeds this value, a red light will illuminate and sound the internal beeper. Refer to page 114 for further info.

ALARM LOW: Gives the user the ability to set the LO limit parameter. If the measurement falls below this value, a red light will illuminate and sound the internal beeper. Refer to page 114 for further info.

DIFFERENTIAL: Gives the user the ability to set a nominal value and the DFX-8 will

display +/- the difference from the nominal value entered. Refer to page 116 for further info.

GAUGE: Gives the user the ability to select between the two gauge types included

in the DFX-8, thickness gauge or flaw detector. Refer to page 5 for further info.

KEY CLICK: Gives the user the ability to set the level of the key press beeper OFF, QUIET, or LOUD. Refer to page 129 for further info.

SET DATE: Gives the user the ability to set the internal date and time stamp in the

DFX-8. Refer to page 130 for further info.

3.12 XFER (transfer) – Menu

COPY SETUPS: Copies setup files from either the internal or external SD memory

card to the other memory card, depending on the current internal/external setting of Storage (current device being used to store data), located in the XFER menu. Refer to page 170 for further info.

COPY DATA:

internal or external SD memory card to the other memory card, depending on the current internal/external setting of Storage (current device being used to store data), located in the XFER menu. Refer to page 170 for further info.

COPY SCREENS:

external SD memory card to the other memory card, depending on the current internal/external setting of Storage (current device being used to store data), located in the XFER menu. Refer to page 170 for further info.

CAPTURE TO FILE: Enables the user the ability to enable screen captures to .tiff files, and used in conjunction with the FREEZE key. Refer to page 132 for further info.

UPGRADE GAUGE: Enables the user the ability to upgrade the DFX-8 to the most

current firmware revision. Refer to page 172 for further info.

Enables the user to copy all, or individual grid/log files from either the

Copies screen capture (.tif’s) files from either the internal or

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STORAGE: Enables the user to select which SD memory card to use for storage. Note: if no card exists in the external reader slot, this option will be grayed out and inactive. Refer to page 169 for further info.

ABOUT: Provides the user with Dakota Ultrasonics contact information and the

DFX-8 software version. Refer the Dakota Ultrasonics web site for information on the

latest firmware versions available for download.

3.13 CLR (clear) Key

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

3.14 MEAS (measurement mode) Key

The MEAS key puts the DFX-8 into it’s primary mode of operation. In this mode, the

user has a complete view of the LCD.

3.15 OK Key

The primary function of the OK key is confirmation of a change or selection. The OK key also toggles the Hot Menu area, while in measurement mode, to a large digits

display area. If the DFX-8 is displaying a grid log, the OK key toggles an advance to

row number option.

3.16 ESC Key

The ESC key is used in the MENU, MEAS, and EDIT functions as a back or escape

function. If the DFX-8 is displaying a grid or sequential log, the OK key toggles the

display options: Digits, RF, RECT, and B-Scan views.

3.17 Wheel Keys

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

3.18 ENTER key

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

3.19 MULTI MODE Key

The MULTI MODE key opens a measurement mode screen, listing all the modes that are available to the transducer specifically selected, or auto detected. The modes

can be all or a combination of the entire set of modes the DFX-8 offers, depending on

which transducer is being used as follows: Coating Off (P-E), Coating On (PECT),

Temp Comp (PETP), Thru Coat (E-E), Thru Coat Verify (E-EV), and Coating Only (CT).

3.20 DATA Key

The DATA key opens the tabbed data menu, allowing a user to efficiently create a new log/grid file for storage.

3.21 STORE Key

The STORE key displays the current log/grid opened in split screen mode. If no log/grid file is open, the STORE key will open the tabbed data menu in order create a new, or open an existing log/grid file for storage.

3.22 PEAK Key

The PEAK key is a feature used in the flaw detector portion of the DFX-8, and is not

used in the thickness gauge.

3.23 FREEZE Key

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The FREEZE key is used to freeze the display for evaluation/review of what’s currently on the display. It is also used in conjunction with the CAPTURE feature to save the current display to a .tif (tagged image) graphic file that can be opened using any graphics viewer.

3.24 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 automatically saved prior to powering off.

3.25 Navigating the Hot Menus

The diagram above is a screenshot of all 8 “Hot Menus” in the DFX-8. The Hot Menu’s contain all the most regularly adjusted features from each tabbed menu, in the exact order of the tabbed menus themselves. Some of the menus have been combined into a single Hot Menu, in order to reduce the number of Hot Menus (i.e. GT1 & GT2 have been combined into a single Hot Menu). The primary purpose of the design was to provide the user with an efficient way to make adjustments on the fly, while continuing to have visibility of the A-Scan display. The following procedure outlines the steps to navigate and make adjustments as follows:

Navigating Hot Menus

1) Using the left button wheel, press the LEFT and RIGHT arrow keys to

scroll through the 8 individual Hot Menus, and the UP and DOWN

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arrow keys to scroll through the Hot Menu items. Alternatively, the MEAS &

ESC keys can be used to scroll through the Hot Menu items.

2) Press the LEFT and RIGHT arrow keys multiple times on the right

button wheel to toggle the value or status.

Note: This is a coarse adjustment. It’s the fastest and easiest way to

increment, decrement, or toggle the status however it does so in coarse steps.

Pressing the ENTER key will allow the user to enter a specific target value.

This procedure above is universal for navigating through and selecting all the features in the Hot Menus.

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3.26 Top & Bottom End Caps

The top & bottom end panels are where all connections are made to the DFX-8. The

diagram above shows the layout and description of the connectors:

Transducer Connectors

Refer to Diagram: The transducer connectors, emergency battery backup channels/probe zero disks, power connector and auxiliary connector are located on

the DFX-8’s top end cap. The transducer connectors are of type Lemo “00”. Note: There is no polarity associated with connecting the transducer to the DFX-8.

Probe Zero Disk & Battery Cover

Refer to Diagram: The emergency battery backup disks are the large round disks

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) for each. When performing a manual probe zero function, simply place the transducer on disk making firm contact. Important: Be sure to follow the polarity label located on the back label

of the DFX-8. Note: Rechargeable batteries can be used, however they must be

recharged outside of the unit in a standalone battery charger.

USB Type B Connector

Refer to Diagram: The USB connector is a common type B connector found on a

variety of electronic devices. This port will be used to transfer stored grid/log files,

captured screen shots, etc. This connector will also be used to upgrade the DFX-8

with the latest version of firmware (gauge software). The cable supplied with the

DFX-8 is USB type A to USB type B.

RS-232 Serial Connection (LEMO 1 – 5 pin)

Refer to Diagram: The RS-232 connector is a 5 pin female Lemo 1 connector. It is

designed to connect directly from the DFX-8 to a standard AT serial port on a PC,

and will be used in conjunction with our proprietary java application software called “Remote Commander”. The primary purpose of the Remote Commander software, will be for use in conjunction with a projector connected to a PC for classroom training programs and demonstration purposes. An accessory 9 pin female serial to Lemo 1 - 5 pin male cable will be required to use this feature, and is not included in the standard kit.

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Alarms Connection (LEMO 1 – 5 pin)

Refer to Diagram: The RS-232 connector is a 5 pin female Lemo 1 connector. This

is used for connecting each alarm directly to an external source. An accessory 9 pin female serial to Lemo 1 - 5 pin male cable will be required to use this feature, and is not included in the standard kit.

Power Connector (LEMO 1 – 2 pin)

Refer to Diagram: The Lemo 1 2 pin connector is used for direct line power and

charging the Li-Ion battery pack.

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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 100 feet 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

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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 900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 pulse-echo mode has larger errors due to changes in the temperature of the delay line. However, multi-echo techniques offer temperature compensation help to minimize these errors.

4.6 Measurement Modes

In this section we will discuss the different measurements modes the DFX-8 is

capable of operating in, the transducers required, and the reasons for using specific modes:

Pulse-Echo Mode (Flaw & Pit detection) – Coating Off (P-E)

Pulse-echo mode measures from the initial pulse (sometimes referred to as an artificial zero) to the first echo (reflection). In this mode, either an automatic or manual zero can be performed depending on the zero probe function setting. If the manual mode has been selected, the transducer is placed on a reference disk,

located on top of the DFX-8, and a key is pressed to establish a zero point for the

particular transducer. If the Auto Zero feature is enabled, a simple key press will perform an electronic zero to establish the same zero point.

In this mode errors result from surface coatings and temperature variations. Since pulse-echo only requires one reflection, it is the most sensitive mode for

measuring weak reflections (flaws) typically found when measuring heavily corroded metals.

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V-Path Correction

Dual element delay line transducers have two piezoelectric elements mounted at an angle on one end of the delay line. One element is used for transmitting sound, while the other element only receives sound. The two elements and their delay lines are packaged in a single housing but acoustically isolated from each other with a sound barrier. This allows the transducer the ability to achieve very high sensitivity for detecting small defects. Also, the surface of the test material does not have to be as flat in order to obtain good measurements.

Dual element transducers are normally used in pulse-echo mode for finding defects, and in echo-echo mode for through coating measurements.

Dual element delay line transducers are usable over a range starting as thin as 0.025 inches and up, depending on the material, frequency, and diameter.

A limitation of dual element delay-line transducers is the V shaped sound path. Because the sound travels from one element to another, the time versus thickness relationship is non-linear. Therefore, a correction table in the instruments software is used to compensate for this error.

Dual Element Transducer showing V-path of signal

Searching for small defects

Dual element delay line transducers are especially useful in searching for small defects. In the pulse-echo mode with high amplifier gain, very small defects can be measured. This is very useful during corrosion inspections overall. The dual element style transducer will find wall deterioration, pits, and any porosity pockets during tank and pipeline inspections.

Echo-Echo Mode – Thru Coat (E-E)

The echo-echo mode measures between two reflections. This technique is commonly used to eliminate errors from surface coatings and also to make measurements in multiple layered materials. The disadvantage is that two echoes are needed which requires a much stronger echo (reflection).

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Dual Element Transducer in Echo to Echo mode

Echo-Echo Verify Mode – Thru-Verify (E-EV)

The echo-echo verify mode measures between 3 reflections. Similar to E-E mode, this technique is commonly used to eliminate errors from surface coatings and also to make measurements in multiple layered materials. The primary benefit of this mode, is that a comparison is made, between the 2nd and 3rd echoes, to verify that a peak jump has not occurred, providing an additional level of confidence to the measurement. The disadvantage is that 3 reflections are needed which requires the use of gates with controllable thresholds to adjust for sensitivity over a given measurement range.

Dual Element Transducer in Echo to Echo mode

Pulse Echo Coating Mode – Coating On (PECT)

A custom hybrid combination mode using properties from the basic modes along with a group of special techniques and theoretical wave phenomena’s to measure coating and material thicknesses at the same time, while still retaining the ability to locate flaws and pits in materials. Therefore, the best description for this hybrid mode is Pulse-Echo Coating mode.

Coating Mode – Coating Only (CT)

Once again, this is a custom hybrid combination mode using special techniques to effectively measure the thickness of coatings that are either adhered to metallic surfaces or in standalone form. In this mode a two point calibration must be performed. If the user will be measuring coating that has been applied to a metal surface, the calibration must be performed using coating samples coupled to a metal surface when calibrating. To explain further, a drop of couplant must be applied in between the coating samples and metal surface. If the coating has not been applied to a metal surface, the calibration should be performed accordingly.

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Pulse-Echo Temperature Compensated Mode – Temp Comp (PETP)

This is a custom mode that combines pulse-echo and electronic zero techniques to automatically adjust for temperature changes in the transducer as a result of an increasing/decreasing temperature gradient in the test material. Note: rough surface conditions can have an effect on the overall accuracy in this mode. If the surface condition is in question, the pulse-echo mode should be used in conjunction with performing an off block automatic zero as the temperature gradient changes.

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CHAPTER FIVE SELECTING THE MEASUREMENT MODE

5.1 The setup library

The DFX-8 contains 64 user configurable 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 cover some of the more typical applications commonly used with this type of instrument. These setups can be recalled, modified, and overwritten to one of 64 setup locations. Therefore, these factory setups can also be considered a good starting point to be modified for custom applications. The PC software includes a default setup file that can be uploaded to the gauge at any time to restore factory settings. However, it is recommended that the user consider saving modified setups to an empty location rather than overwriting the factory setups

in the DFX-8. 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. The DFX-8 has been optimized for cast materials. Cast iron applications require 1 - 5MHz frequencies, and cast aluminum requires a 10MHz frequency. Plastics typically require lower frequencies depending on the thickness and make-up of the material. Larger diameters offer greater penetration power because of the crystal size, for difficult to measure materials.

Corrosion & Pit Detection in steel and cast materials

Use pulse-echo mode whenever attempting to locate pits and flaws. Typically a 5MHz transducer, or higher, will be used for these types of applications. Use low frequencies for greater penetration and use higher frequencies for better resolution.

Measuring Material & Coatings

The pulse-echo coating mode should be used when both material and coating thickness are required, while still requiring the ability to detect flaws and pits. A special coating style transducer is required for use in this mode. There are a variety of coating transducers in various frequencies available from Dakota.

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Thru Paint & Coatings

Often times, 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. Users will often use pulseecho mode and echo-echo mode in conjunction when performing inspections on coated materials.

Thru coating measurements require special high damped transducers. The most common transducers are the 3.5, 5, and 7.5MHz hi damped transducers. These transducers are suitable for use in both pulse-echo and echo-echo modes. This conveniently enables the user to accurately measure overall material thickness using the thru Coating mode, and then conveniently switch to pit detection mode without changing transducers. The ¼” 5MHz Hi damped transducer is the most commonly used transducer for standard thru coating applications.

Coating Only The coating only mode should be used when the application calls for coating

measurements only and the user is not interested in the thickness of the material the coating has been applied to. This mode can also be used as a standalone coating thickness gauge, where the coating has not been applied to another material surface.

An auto identified coating probe must be attached to the DFX-8 in order to enable

this mode.

Thin materials

Use pulse echo mode and a high frequency transducer for these types of applications. The most common transducers are the 7.5MHz and 10MHz models with extra resolution. The higher frequencies provide greater resolution and a lower minimum thickness rating overall.

High temperature

Use and select a special 2.25MHz and 5 MHz High temperature transducer for these types of applications. Both pulse-echo and echo-echo modes will also work for these applications. However, echo-echo mode will eliminate error caused by temperature variations in the delay line of the transducer.

Noisy Material

Materials such as titanium, stainless steel, and aluminum may have inherent surface noise issues. This is a signal that appears at the surface of the material when using a dual element delay line probe. Select a higher frequency transducer to reduce this noise – 7.5MHz and higher for better resolution.

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DFX-8 Ultrasonic Thickness Gauge

Restricted access

Measuring materials with extreme curvatures or restricted access, higher frequencies with smaller diameters should be considered. The smallest diameter uses 3/16” crystals with a contact area of .250”. Custom transducers are available on request.

5.3 Factory Setup Chart

Num Name Comment 1 Gn/AGC Velocity

1 Enter Custom Name 2 … 3 … 4 … 5 … 6 … … …

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CHAPTER SIX MAKING MEASUREMENTS

The steps involved in making measurements are detailed in this section. The

following sections outline how to setup and prepare your DFX-8 for field use.

An automatic or manual zero must always be performed. The auto zero is an off block electronic zero that does not require a zero reference block. This will most always be the zero option of choice, as it makes the zeroing process very easy and convenient to perform. However, If the manual zero option is enabled, the probe zero must be measured on the reference disk (battery disk) attached to the top of the instrument. The zero compensates for variations in the transducer. In all modes the sound velocity must be determined. The sound velocity is used to convert the transit time to a physical length. The sound velocity can be selected from a material chart in

the manual, selected from a material list in the DFX-8, or for greater precision

determined from a sample of the test material that has been mechanically measured. To enter the velocity from a table, look up the material on the chart in the appendix of this manual and refer to the section below on Calibration to a Known Velocity. To determine the velocity of a single sample, refer to the Material Calibration section on page 57.

When measuring curved materials, it is more accurate to calibrate from two test points, one at the minimum limit of the target thickness and one at the maximum limit.

In this case the reference disk mounted to the DFX-8 is not used. This is called two-

point calibration and is described on page 59.

6.1 Auto Probe Recognition & Selecting the Transducer Type

The first step in using the DFX-8 is to plug the transducer into the gauge and power the unit up. The DFX-8 has a special built-in automatic probe recognition feature that

will check to see if the probe plugged into the gauge is an auto recognized probe

type. If so, the DFX-8 will display a message indicating the transducer type and ask

the user for confirmation to use the identified probe. If the transducer is not an auto

recognized probe, the DFX-8 will display a message indicating the transducer type

has not been recognized, and force the user to select a transducer type from a list of transducers according to frequency and diameter. Whether the transducer is auto

recognized or selected from a predefined list, the DFX-8 will recall specific properties about the transducer. Note: Once the transducer has been selected, the DFX-8 will store and recall this transducer type every time the DFX-8 is powered on/off. The

type will only change if the user physically selects another type from the list, or selects a previously saved setup. Therefore, if you have previously gone through this section and selected the transducer you are using, proceed to the next section. Use the following steps to select your transducer type. Note: If the transducer is not identified on power up, be sure the transducer type selected is the same as the transducer plugged into the DFX-8. Failure to do this will result in erroneous measurements:

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In this first example the transducer was automatically identified:

Probe Automatically Recognized

1) Press the OK key once to use the identified probe, or ESC to display a list of

optional transducers. Note: if the DFX-8 recognizes a specific transducer,

the user should always select OK to use the identified probe. The only time an alternative probe should be selected from a list is if the user switched probes following initial power up and recognition, or the DFX-8 has somehow identified the probe in error..

2) Assuming the DFX-8 recognized the probe and the OK key was pressed, the DFX-8 will advance to a Zero Probe menu. If the transducer was

identified as a special transducer capable of measuring coating thickness, a

menu will be displayed allowing the user the ability to toggle the coating

thickness display on/off as follows:

3) Press the UP and DOWN arrow keys on the left button wheel to toggle

the coating option on/off.

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4) Wipe all couplant from the transducer face and proceed to the Probe Zero

section that follows.

In this second example the transducer was not identified and will force the user to select the transducer type from a predefined list of transducers:

Selecting the Transducer Type

5) Press the OK or ESC keys to display the factory list of transducer types (by

diameter and frequency).

6) Press the UP and DOWN arrow keys on the left button wheel to scroll

through the transducer list until the appropriate type is highlighted.

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DFX-8 Ultrasonic Thickness Gauge

7) Press the ENTER key to select the transducer type and display overwrite

existing probe screen.

8) Press the OK key to overwrite the existing probe type with the newly

selected probe type. The zero probe screen will be displayed. Proceed to

the zero probe section that follows.

6.2 Probe zero

The next step is to perform a probe zero. The zero function is a very important and necessary function that must be done prior to calibration. It should be done on a

regular basis. In fact, the DFX-8 has been programmed to force this issue at regular intervals during operation if it hasn’t been done. If the DFX-8 is not zeroed correctly, all the measurements taken may be in error by some fixed value. When the DFX-8 is using the auto zero (electronic zero), the DFX-8 can be in any measurement mode. However, when the manual zero is being used, the DFX-8 must be in pulse-echo mode in order to perform the zero. The DFX-8 will also see to it that this occurs by simply forcing the gauge into this mode when zero. Therefore, if the DFX-8 is in the echo-echo measurement mode and a manual zero is being performed, the DFX-8 will

put the gauge into pulse-echo mode automatically before performing the zero. While

this is a very convenient feature of the DFX-8, the user should be sure to check the measurement mode following calibration to be sure the DFX-8 is in the desired mode.

The following steps outline both of these techniques.

The DFX-8 is equipped with two zero options:

1) Off Block Zero (Automatic Probe Zero) – When this feature is enabled the

DFX-8 will do an electronic zero automatically, eliminating the need for a zero

disk or block.

2) On Block Zero (Manual Probe Zero) – When this feature is enabled the transducer must be placed on the probe zero disk (battery cover located on the top of the unit.

Both zero procedures are outlined as follows:

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Performing an Auto Probe Zero (Off Block)

Coating Probe Identified Coating Probe Not Identified

1) Be sure all couplant has been removed from the face of the transducer.

2) Press the OK key to perform the automatic probe zero, or ESC key to

cancel the zero operation.

3) The screens illustrated above will be briefly displayed followed by the main

measurement screen. The DFX-8 is ready to be calibrated.

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DFX-8 Ultrasonic Thickness Gauge

Performing a Manual Probe Zero (On Block)

Note: When the zero probe option is set to manual, the probe zero disk

(battery cap) located on the top of the gauge will be used as a zero standard

and the warning screen illustrated above will be displayed.

1) Press the OK or ESC keys to enter the main measurement screen and

begin the manual zero process.

2) Apply a drop of couplant on the transducer and place the transducer in

steady contact with the probe zero disk and obtain a steady reading.

3) 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 PRB menu is highlighted and displaying the submenu items.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel.

4) Press the UP and DOWN arrow keys on the left button wheel to scroll

through the sub menu items until ZERO PROBE is highlighted.

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Coating Probe Identified Coating Probe Not Identified

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

6) If a coating transducer was identified use the UP and DOWN arrow

keys on the left button wheel to toggle coating on/off.

7) Press the OK key to complete the probe zero function, or ESC key to cancel

the probe zero function.

8) Remove the transducer from the probe zero disk, and proceed to the

calibration section.

Note: The value that is displayed will change depending on the current velocity

setting in the DFX-8. Disregard the number that is displayed. It is not

important. What is important is accurately performing the steps outlined above

to insure reliability of the probe zero calculation.

6.3 Material Calibration

In order for the DFX-8 to make accurate measurements, it must be set to the correct

sound velocity of the material being measured. Different types of materials have different inherent sound velocities. For example, the velocity of sound through steel is about 0.233 inches per microsecond, versus that of aluminum, which is about

0.248 inches per microsecond. If the gauge is not set to the correct sound velocity, all of the measurements the gauge makes will be erroneous by some fixed percentage.

The One Point calibration is the simplest and most commonly used calibration method - optimizing linearity over large ranges. The Two Point calibration allows for

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DFX-8 Ultrasonic Thickness Gauge

greater accuracy over small ranges by calculating the probe zero and velocity. The

DFX-8 provides four simple methods for setting the sound-velocity outlined below:

Known Velocity

If the material velocity is known, the user may wish to simply enter the velocity

number into the DFX-8, rather than have the DFX-8 calculate the velocity value using

a known thickness on a material sample. 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.

Alternatively, press the LEFT and RIGHT arrow keys multiple times

using the left button wheel.

2) Press the UP and DOWN arrow keys multiple times using the left button

wheel to scroll through the sub menu items until VELOCITY is highlighted.

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

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4) Press the UP and DOWN arrow keys multiple times using the left button

wheel to scroll the highlighted value.

5) Press the LEFT and RIGHT arrow keys multiple times using the left

button wheel 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.

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Known Thickness

Sometimes the sound velocity of a material is unknown. In this case a sample with one or two known thicknesses can be used to determine the sound velocity. As

previously discussed, the DFX-8 has a one or two point calibration option. The one

point calibration option is most suited for linearity over large ranges, as noted above. The user should also consider calibrating on high side of the intended measurement range, when using the one point option, minimize overall error. For example, if the measurement range is .100” (2.54mm) to 1.0” (25.4mm), the user should calibrate on a known thickness sample close to 1.0” (25.4mm). Note: It’s always handy to carry a

set of mechanical calipers to use in conjunction with the DFX-8 for calibration in the

field:

One Point Calibration