Dakota Ultrasonics MMX-7 Operating Manual v2.0
OPERATION MANUAL
DAKOTA ULTRASONICS
0
MMMMXX--77
Data Logging Ultrasonic Thickness Gauge
vv22..0
P/N P-160-0004 Rev 3.0, April 2019
CONTENTS
CHAPTER ONE INTRODUCTION ...................................................................... 1
DISCLAIMER ......................................................................................................................... 1
1.1
CHAPTER TWO QUICK STARTUP GUIDE ....................................................... 2
2.1
MMX-7 OVERVIEW ............................................................................................................... 2
2.2
SELECTING THE TRANSDUCER TYPE ..................................................................................... 4
2.3
PROBE ZERO & CALIBRATION ............................................................................................... 5
MEASURE .......................................................................................................................... 10
2.4
CHAPTER THREE KEYBOARD, MENU, & CONNECTOR REFERENCE ...... 13
3.1
MENU KEY (OPERATION & SUB MENUS) .............................................................................. 13
3.2
PROBE – MENU .............................................................................................................. 15
3.3
CAL – MENU .................................................................................................................. 15
3.4
DISP (DISPLAY) – MENU ............................................................................................ 16
SETUP – MENU ............................................................................................................. 16
3.5
3.6
DATA – MENU ............................................................................................................... 17
3.7
UTIL (UTILITIES) – MENU ................................................................................................ 17
3.8
XFER (TRANSFER) – MENU ............................................................................................ 18
3.9
CLR (CLEAR) KEY ........................................................................................................ 18
MEAS (MEASUREMENT MODE) KEY ............................................................................... 18
3.10
3.11
OK KEY ....................................................................................................................... 19
3.12
ESC KEY ..................................................................................................................... 19
3.13
ARROW KEYS ............................................................................................................... 19
3.14
ENTER KEY ................................................................................................................. 19
MULTI MODE KEY ...................................................................................................... 19
3.15
3.16
ON/OFF KEY .............................................................................................................. 20
3.17
TOP & BOTTOM END CAPS ............................................................................................... 21
CHAPTER FOUR PRINCIPALS OF ULTRASONIC MEASUREMENT ........... 22
4.1
TIME VERSUS THICKNESS RELATIONSHIP ............................................................................. 22
4.2
SUITABILITY OF MATERIALS ................................................................................................. 22
RANGE OF MEASUREMENT AND ACCURACY .......................................................................... 22
4.3
4.4
COUPLANT ......................................................................................................................... 22
4.5
TEMPERATURE ................................................................................................................... 23
4.6
MEASUREMENT MODES ...................................................................................................... 23
CHAPTER FIVE SELECTING THE MEASUREMENT MODE ......................... 26
5.1 THE SETUP LIBRARY ........................................................................................................... 26
5.2
WHICH MODE & TRANSDUCER DO I USE FOR MY APPLICATION? ............................................ 26
5.3
FACTORY SETUP CHART .................................................................................................... 27
CHAPTER SIX MAKING MEASUREMENTS ................................................... 28
6.1
SELECTING THE TRANSDUCER TYPE ................................................................................... 28
6.2
PROBE ZERO ..................................................................................................................... 30
6.3
MATERIAL CALIBRATION ..................................................................................................... 32
CHAPTER SEVEN USING THE DISPLAY OPTIONS ..................................... 41
7.1
DISPLAY VIEWS .................................................................................................................. 42
CHANGING DISPLAY OPTIONS ............................................................................................. 44
7.2
7.3
ADJUSTING THE DISPLAY .................................................................................................... 45
7.4
GAIN ................................................................................................................................. 48
CHAPTER EIGHT THRU PAINT MEASUREMENT TECHNIQUE................... 51
8.1
INTRODUCTION TO THRU PAINT MEASUREMENT .................................................................. 51
USING THRU PAINT MODE .................................................................................................. 51
8.2
CHAPTER NINE ADDITIONAL FEATURES OF THE MMX-7 ......................... 52
9.1
HIGH SPEED SCAN ............................................................................................................. 52
9.2
ALARM MODE .................................................................................................................... 53
9.3
DIFFERENTIAL MODE .......................................................................................................... 55
KEY CLICK ......................................................................................................................... 56
9.4
9.5
SET DATE & TIME .............................................................................................................. 57
9.6
SHOW DATE & TIME ........................................................................................................... 59
9.7
FREEZE & CAPTURE ........................................................................................................... 59
CHAPTER TEN DATA STORAGE – SETUP, EDIT, & VIEW FILES ............... 62
10.1
INTRODUCTION TO THE GRID FILE FORMAT ........................................................................ 62
CREATING A NEW GRID .................................................................................................... 63
10.2
10.3
STORING A READING ........................................................................................................ 71
10.4
VIEWING STORED READINGS ............................................................................................. 72
10.5
DELETING GRIDS (FILES) .................................................................................................. 74
10.6
EDITING A GRID (FILE) ...................................................................................................... 77
CHANGING THE ACTIVE FILE - OPEN .................................................................................. 79
10.7
10.8
CLOSING AN ACTIVE FILE - CLOSE .................................................................................... 81
CHAPTER ELEVEN SETUPS – CREATE, STORE, EDIT, & RECALL .......... 84
11.1
INTRODUCTION TO SETUPS............................................................................................... 84
11.2
OPENING A SETUP ........................................................................................................... 84
11.3 SAVING A SETUP .............................................................................................................. 86
11.4
DELETING A SAVED SETUP ............................................................................................... 90
11.5
USING THE DEFAULT SETUP ............................................................................................. 92
SELECTING A LANGUAGE .................................................................................................. 93
11.6
CHAPTER TWELVE USING THE UTILITY SOFTWARE ................................ 94
12.1
COMPUTER SYSTEM REQUIREMENTS ................................................................................ 94
12.2
INSTALLING DAKVIEW ....................................................................................................... 94
12.3
COMMUNICATING WITH THE MMX-7 .................................................................................. 94
12.4
LINE POWER .................................................................................................................... 94
UPGRADING THE MMX-7 .................................................................................................. 94
12.5
APPENDIX A - VELOCITY TABLE .................................................................. 96
APPENDIX B - SETUP LIBRARY .................................................................... 98
CHAPTER ONE
INTRODUCTION
The Dakota Ultrasonics model MMX-7 is a digital ultrasonic thickness gauge with
time based B-Scan and alpha numeric data logger. Based on the same operating
principles as SONAR, the MMX-7 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 Disclaimer
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.
CHAPTER TWO
QUICK STARTUP GUIDE
Turn the MMX-7 on and off using the switch located on the bottom right corner of the
keypad. When MMX-7 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 MMX-7 Overview
In order to understand how to operate the MMX-7, it’s best to start off with an
understanding of what it is we’re looking at exactly. The MMX-7 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 MMX-7 is reliably measuring the same value 250 times per second
(250 Hz).
B. Battery Icon – Indicates the amount of battery life the MMX-7 has remaining.
C. Velocity – The material velocity value the MMX-7 is currently using or
calibrated for. Displayed in both English or Metric units, depending on what
units the gauge is set for.
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MMX-7 Ultrasonic Thickness Gauge
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 Value – Extra large font size for viewing ease.
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. Digital Material Thickness Value – Smaller font size when the B-Scan
display view is enabled.
I. Minimum Material Thickness – Part of the scan feature. Displays the
minimum thickness value found during a scan.
J. Maximum Material Thickness – Part of the scan feature. Displays the
maximum thickness value found during a scan.
K. 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.
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2.2 Selecting the Transducer Type
The MMX-7 is equipped with a transducer list of all of the dual element transducer
options that can be connected to the gauge. These are dual element transducers
with different diameters and frequencies, depending on the material and application
requirements. Transducers with an HD (high damped) designation are commonly
used in conjunction with E-E (echo-echo) through paint modes, while CPZT
(composite) are used for additional output with materials that are difficult to pass
sound through. Finally, the majority of the transducers listed in the table are standard
diameter/frequency transducers used in P-E (pulse-echo) mode. By selecting the
transducer type from a predefined list, the MMX-7 can recall specific properties about
the transducer.
Note: Once the transducer has been selected, the MMX-7 will store and recall this
transducer type every time the MMX-7 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. 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:
Selecting the Transducer Type
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 PRB menu is highlighted and displaying the submenu items.
2) Use the UP and DOWN arrow keys to scroll through the sub menu items
until TYPE is highlighted.
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MMX-7 Ultrasonic Thickness Gauge
3) Press the ENTER key to display the table/list of transducers.
4) Use the UP and DOWN arrow keys to highlight the transducer type currently
connected to the gauge.
5) Press the ENTER key to load the transducer type and display the
confirmation screen.
6) Press the OK key to overwrite the existing probe type, or ESC to cancel.
2.3 Probe Zero & Calibration
The next steps are to perform a probe zero and calibrate the MMX-7 to the material
and transducer selected. If the sound velocity is unknown, the MMX-7 can be
calibrated to a known thickness sample. The procedures are outlined as follows:
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Performing a Probe Zero
Note: The probe zero disk (battery cap) is located on the top end cap of the
gauge. The warning screen will be displayed following the selection and
overwrite of a new transducer.
1) Press the OK key 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.
3) With the “zero probe” hot menu cell highlighted by default, press the ENTER
key to display the confirmation screen, followed by pressing the OK key to
perform the zero.
Note: If the “zero probe” cell is not highlighted, press the MEAS or ESC keys
to highlight.
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MMX-7 Ultrasonic Thickness Gauge
4) Alternatively, 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.
5) Press the UP and DOWN arrow keys to scroll through the sub menu items
until ZERO PROBE is highlighted.
6) Press the ENTER key to display the confirmation screen.
7) Press the OK key to complete the probe zero process, or ESC key to cancel
zeroing.
8) Remove the transducer from the probe zero disk, and proceed to the
calibration section.
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Note: The value that is displayed will change depending on the current velocity
setting in the MMX-7. 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, the most common single point calibration
option will covered in this section.
Note: It would be very handy to carry a set of mechanical calipers to use in
conjunction with the MMX-7 for calibration in the field.
Known Thickness
Note: Be sure a probe zero has been performed prior to calibration.
1) Physically measure an exact sample of the material, or a specific location
directly on the material 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 measured. Be sure
the measurement 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
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MMX-7 Ultrasonic Thickness Gauge
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 MATL 1PT 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.
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.
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2.4 Measure
The MMX-7 is now ready to measure. There are two different measurement view
options each with a specific purpose – Digits & 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.
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: Displays the digital thickness value using a large font size. This view is
useful when the MMX-7 is being used as a basic thickness gauge.
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
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MMX-7 Ultrasonic Thickness Gauge
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 B-
Scan Start (B-ST) and Depth (B-DEP) will potentially need adjustment in order to
optimize the zoom if the MMX-7 has been set to B-Scan.
Use the following steps to adjust these settings directly from the measurement
screen as follows:
Note: The B-Start and B-Depth are also used to adjust the parameters of Scan
Bar.
Adjusting B-Start & B-Depth
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 B-ST and B-
DEP 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.
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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.
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-START & B-DEPTH can also be adjusted from the tabbed menu
item DISP. However, using the hot menu keys is the most convenient method.
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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 8 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.
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 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, 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:
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MMX-7 A/B Scan Thickness Gauge
3.2 Probe – Menu
ZERO PROBE: The MMX-7 is zeroed in much the same way that a mechanical
micrometer is zeroed. If the MMX-7 is not zeroed correctly, all of the measurements
made using the MMX-7 may be in error by some fixed value. The MMX-7 is
equipped with an optional automatic or manual zero feature. Refer to the section on
page 30, for an explanation of this important procedure.
TYPE: Enables the user to select the type of transducer being used from a chart of
transducer types. This provides increased linearity between transducers. Refer to
page 4 for a further explanation.
MEASURE MODE: Toggles between the measurement modes; pulse-echo (P-E) and
echo-echo (E-E). Refer to page 23 for further info.
GAIN: Active only if the measure mode is set to pulse-echo (P-E), and is used to
increase/decrease the overall amplitude of the signal. The gain can be adjusted
using a three position switch with LOW, MED, HI settings. MED is set to 46 dB, with
a 3 dB cut or boost. Consider it as similar to turning the volume up or down on a
stereo receiver. Refer to page 48 for further info.
AGC: Active only if the measure mode is set to echo-echo (E-E), and is used to
increase/decrease the over amplitude of the signal. The gain can be adjusted using
a three position switch with LOW, MED, HI settings. The AGC target is defined as
MED, with a 3 dB cut/boost. Refer to page 48 for further info.
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 38 for
further info.
MATL 1PT:
automatically calculate the velocity by entering a known sample thickness. Refer to
page 35 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 37 for further info.
Performs a single point calibration. This option allows the user to
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VELOCITY: Function to calibrate the MMX-7 by setting the velocity to a known
material velocity. Refer to page 32 for further info.
3.4 DISP (display) – Menu
VIEW:
page 42 for further info.
B-START:
view. Adjusts the range of the scan bar in digits view. Refer to page 43 for further
info.
B-DEPTH: Provides the user the ability to change the overall depth of the viewable
measurement area. Adjusts the range of the scan bar in digits view. Refer to page
46 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 46 for further info.
UNITS: Toggle between English or Metric units. The readout will change from
inches to millimeters (0.001” / 0.01mm).
BACKLIGHT: Selectable OFF, ON, AUTO, or INVERT backlight option.
CONTRAST: Adjustable display contrast for variable light conditions.
Selectable BSCAN (cross section), and DIGITS (large digits) views. Refer to
Provides the user the ability to change the start position of the B-SCAN
3.5 SETUP – Menu
OPEN:
These setups can be recalled and used at any time. Refer to page 84 for further info.
SAVE: Provides the user with the ability to save a custom setup that has been
modified or created by the user. Refer to page 86 for further info.
DELETE: Provides the user with the ability to delete specific setups previously save
in memory. Refer to page 90 for further info.
Displays a list of factory and user defined setups currently stored in memory.
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MMX-7 A/B Scan Thickness Gauge
DEFAULT SETUP: Loads a basic default setup. Use only as a last resort when the
setups in the MMX-7 have been corrupted and a computer is not accessible. Refer to
page 92 for further info.
LANGUAGE: Provides the user the ability to select different languages for the MMX-
7. Refer to page 93 for further info.
3.6 DATA – Menu
NEW:
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
63 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 77 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 79 for further
info.
CLOSE: Provides the user the ability to close a currently opened grid or sequential
log file. Refer to page 81 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 74 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 75 for further info.
Allows the user the ability to create a new alpha numeric grid, or sequential
3.7 UTIL (utilities) – Menu
SCAN MODE:
overall sample rate from 65 to 200 measurements per second, depending on the
current measurement mode used. Refer to page 52 for further info.
This function enables a high speed scan mode that increases the
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ALARM: Toggles alarm mode on, off, or audible. Refer to page 53 for further info.
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 53 for further info.
ALARM LOW:
measurement falls below this value, a red light will illuminate and sound the internal
beeper. Refer to page 53 for further info.
DIFFERENTIAL:
will display +/- the difference from the nominal value entered. Refer to page 55 for
further info.
KEY CLICK: Give the user the ability to set the level of the key press beeper, OFF,
QUIET, or LOUD. Refer to page 56 for further info.
SET DATE: Gives the user the ability to set the internal date and time stamp in the
MMX-7. Refer to page 57 for further info.
SHOW DATE: Gives the user the ability to display the date and time in the waveform
area of the MMX-7. The options are OFF, DATE, TIME, BOTH. Refer to page 59 for
further info.
Gives the user the ability to set the LO limit parameter. If the
Gives the user the ability to set a nominal value and the MMX-7
3.8 XFER (transfer) – Menu
UPGRADE GAUGE: Enables the user the ability to upgrade the MMX-7 to the most
current firmware revision. Latest version posted on www.dakotaultrasonics.com.
ABOUT: Provides the user with Dakota Ultrasonics contact information and the
MMX-7 firmware version. Refer to the Dakota Ultrasonics web site for information on
the latest firmware versions available for download.
3.9 CLR (clear) Key
The primary functions of the CLR key is to clear a measurement from a grid file cell
location, set an obstruct, or 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.
3.10 MEAS (measurement mode) Key
The MEAS key returns the MMX-7 to the primary measurement screen/view. Press
at any time to view the main screen.
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MMX-7 A/B Scan Thickness Gauge
3.11 OK Key
The primary function of the OK key is confirmation of a change or selection.
Additionally, the OK key also toggles the Hot Menu area to a large digits display
while in measurement mode. If the MMX-7 is displaying a grid log, the OK key
toggles an advance to row number option.
3.12 ESC Key
The ESC key is used in the MENU, MEAS, and EDIT functions as a back or escape
function. If the MMX-7 is displaying a grid or sequential log, the ESC key toggles the
display options: Digits or B-Scan views.
3.13 Arrow Keys
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, display and save measurements to grid file location.
3.15 MULTI MODE Key
The MULTI MODE key opens a measurement mode screen that lists all the modes
available for the transducer selected. The two modes available are pulse-echo (P-E)
and echo-echo (E-E). The high damped transducers will offer both modes, while the
majority will only offer pulse-echo. An additional menu item “capture To File” is also
available when pressing the MULTIMODE key. This allows a user to capture a
screenshot of any measurement screen, menu, or list to a .tif file stored on the
internal SD card.
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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 automatically saved prior to powering off.
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3.17 Top & Bottom End Caps
The top & bottom end panels are where all connections are made to the MMX-7. The
diagram above shows the layout and description of the connectors:
Transducer Connectors
Refer to Diagram: The transducer connectors and battery cover/probe zero disk are
located on the MMX-7 top end cap. The transducer connectors are of type Lemo
“00”.
Note: There is no polarity associated with connecting the transducer to the MMX-7.
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 manual probe zero
function, simply place the transducer on disk making firm contact. Important: Be
sure to follow the polarity labels located on the back label of the MMX-7.
Note: Rechargeable batteries can be used however they must be recharged outside
of the unit in a stand-alone battery charger.
USB-C Connector
Refer to Diagram: The USB-C connector, located on the bottom end cap, is a mini
type C female connector. It is designed to connect directly from the MMX-7 to a
standard USB type A port on a PC. The cable supplied with the MMX-7 is a USB
type C to a USB type A (pt# N-003-0330).
Note: This connector is also used to upgrade the MMX-7 with the latest version of
firmware.
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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 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
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MMX-7 A/B Scan 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 0F to 180F.
High temperature measurements
Special transducers and couplants are available for temperatures above 180F up to
650F 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 MMX-7 is
capable of operating in, the transducers required, and the reasons for using specific
modes:
Pulse-Echo Mode (Flaw & Pit detection) – (P-E)
Pulse-echo mode measures from the initial pulse (sometimes referred to as an
artificial zero) to the first echo (reflection). A manual probe zero can be performed
while in this mode by placing the transducer on the reference disk located at the top
end cap of the MMX-7 and selecting the ‘zero transducer’ option in the “PRB” menu,
or the ‘zero probe’ option in the hot menu items.
Errors can result from surface coatings and temperature gradients in pulse-echo
mode. Therefore, the zero process should be performed on a frequent basis.
This mode is commonly used to detect flaws and pits, as it only requires one
reflection and adjustable gate to improve sensitivity when measuring heavily
corroded metals.
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Dakota Ultrasonics
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 of 0.025 inches to 20
inches 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, and is useful during corrosion inspections to locate pits, porosity and
cracks during tank and pipeline inspections, for example.
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 applications with
temperature gradients. The disadvantage is that two echoes are required for
measurement. Certain materials can be difficult to pass sound through, making it
hard to successfully achieve multiple echoes.
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