Dakota Ultrasonics PX7 Operating Manual

OPERATION MANUAL

P/N P

-

130

-

0002

Rev

1.60,

January

200

8

DAKOTA ULTRASONICS MODEL PX-7 DL PRECISION THICKNESS GAUGE

Dakota Ultrasonics

Copyright  2008 Dakota Ultrasonics. All rights reserved.

No part of this publication may be reproduced, translated into another
language, stored in a retrieval system, or transmitted in any form or by any
means; electronic, mechanical, photocopying, recording, or otherwise,
without the prior written consent of Dakota Ultrasonics.

Every precaution has been taken in the preparation of this publication.
Dakota Ultrasonics assumes no responsibility for errors or omissions.
Neither is any liability assumed for damages resulting from the use of
information contained herein.

Any brand or product names mentioned herein are used for identification
purposes only, and are trademarks or registered trademarks of their
respective holders.

1500 Green Hills Road, #107 Scotts Valley, CA 95066 USA

Tel [phone] Fax [phone]

www.dakotaultrasonics.com

PX-7 DL Ultrasonic Thickness Gauge

CONTENTS

INTRODU CTION
OPERATION

THE KEYPAD
THE DISPLAY
THE TRANSDUCER
MAKING MEASUREMENTS
CONDITION AND PREPARATION OF SURFACES
CALIBRATION
PX-7 DL MODES & FEATURES

RS232 PORT & DATA LOGGER
TRANSDUCER SELECTION
APPENDIX A: PRODUCT SPECIFICATIONS
APPENDIX B: APPLICATION NOTES

1
3
3
7

9
10
12
13
16
21
28
31
33

APPENDIX C: SOUND VELOCITIES OF COMMON MATERIALS
WARRANTY INFORMATION

35
37
42

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INTRODUCTION

The Dakota Ultrasonics model PX-7 DL is a precision Ultrasonic
Micrometer. Based on the same operating principles as SONAR, the PX-7
DL is capable of measuring the thickness of various materials with

accuracy as high as ± 0.0001 inches, or ± 0.001 millimeters. The principle
advantage of ultrasonic measurement over traditional methods is that
ultrasonic measurements can be performed with access to only one side of
the material being measured.

This manual is presented in three sections. The first section covers
operation of the PX- 7 DL, and explains the keypad controls and display.
The second section provides guidelines in selecting a transducer for a
specific application. The last section provides application notes and a table
of sound velocity values for various materials.

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:

• Dakota Ultrasonics, 1500 Green Hills Road, #107
Scotts Valley, CA 95066 USA

• Telephone: [phone]

• Facsimile: [phone]

• www.dakotaultrasonics.com

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OPERATION

The PX-7 DL interacts with the operator through the membrane keypad
and the LCD display. The functions of the various keys on the keypad are
detailed below, followed by an explanation of the display and its various
symbols.

The Keypad

This key is used to turn the PX-7 DL on and off. When the tool is
turned ON, it will first perform a brief display test by illuminating all of the
segments in the display. After one second, the tool will display the internal
software version number and the current file location and status. After
displaying the version number, the display will show ".0000" (or "0.000" if
using metric units), indicating the tool is ready for use.

The PX-7 DL is turned OFF by pressing the ON/OFF key. The tool has
a special memory that retains all of its settings even when the power is off.
The tool also features an auto-powerdown mode desi gned to conserve
battery life. If the tool is idle for 5 minutes, it will turn itself off.

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The IN/MM key is used to switch back and forth between English and
metric units. This key may be used at any time, whether the tool is
displaying a thickness (IN or MM) or a velocity value (IN/µs or M/s).

The CAL key is used to enter and exit the PX-7 DL's calibration mode.
This mode is used to adjust the sound-velocity value that the PX-7 DL will
use when calculating thickness. The tool will either calculate the sound­velocity from a sample of the material being measured, or allow a known
velocity value to be entered directly. Refer to page 13 for an explanation of
the two CAL functions available.

The MODE key is used to toggle through the various features and
settings of the PX-7 DL ( alarm, diff, scan, gate, back light, and beeper ).

The MODE key is used in conjunction with the arrow and send keys to
enable/disable the features and settings. Refer to page 16 for a further
explanation of the different modes.

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The UP arrow key has three functions. When the PX-7 DL is in
calibration mode, this key is used to increase numeric values on the
display. An auto-repeat funct ion is built in, so that when the key is held
down, numeric values will increment at an increasing rate. When MODE is
activated, the UP arrow key scrolls through the various features and
settings of the PX-7 DL. When the data logging feature has been act ivated
by pressing the MEM key, the UP arrow is used to scroll through the
various files, storage locations, and functions of the data logger. Refer to
page 22 for further information regarding the use of the UP arrow key and
the data logger.

The DOWN arrow key has three functions. When the PX-7 DL is in the
CAL mode, this key is used to decrease numeric values on the display. An
auto-repeat function is built in, so that when the key is held down, numeric
values will decrement at an increasing rate. When MODE is activated, the

DOWN arrow scrolls through the various features and settings of the PX- 7
DL. When the data logging feature has been activated by pressing the

MEM key, the UP arrow is used to scroll through the various files, storage
locations, and functions of the data logger. Refer to page 22 for further
information regarding the use of the DOWN arrow key and the data logger.

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The MEM key en ables/disables the data logging feature of the PX-7 DL.
This key is used in conjunction with the UP/DOWN arrows, SEND, AND
CLR keys (hi-lighted in green). The combination of these keys control the

data logging features of the PX-7 DL. Refer to the section on data logging
page 22.

The CLR key is specifically used with the data logging feature of the
PX-7 DL. This key clears the contents of an entire file, or individual storage
locations. The CLR key is also used to send an obstruct (ObSt) to an
individual storage location. The ObSt symbol would indicate that a the
user was unable to take a reading at a particular location. Refer to the
section on data logging page 22.

The SEND key is used for sending data to internal storage locations,
and external peripheral devices ( serial printer / computer ). The SEND key
is also used to select data logging functions in the PX-7 DL page 22.

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The Display

The numeric portion of the display consists of 4 complete digits
preceded by a leading "1", and is used to display numeric values, as well
as occasional simple words, to indicate the status of various settings.
When the PX-7 DL is displaying thickness measurements, the display will
hold the last value measured, until a new measurement is made.
Additionally, when the battery voltage is low, the entire display will begin to
flash. When this occurs, the batteries should be replaced.

These eight vertical bars form the Stability Indicator. When the PX-7
DL is idle, only the left -most bar and the underline will be on. While the
gauge is taking a measurement, six or seven of the bars should be on. If

fewer than five bars are on, the PX-7 DL is having difficulty achieving a
stable measurement, and the thickness value displayed will most likely be
erroneous.

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When the IN symbol is on, the PX-7 DL is displaying a thickness value
in inches. The maximum thickness that can be displayed is 1.999 inches.

When the MM symbol is on, the PX- 7 DL is displaying a thickness value
in millimeters. If the displayed thickness exceeds 19.999 millimeters, the
decimal point will shift automatically to the right, allowing values up to 99.99
millimeters to be displayed.

When the IN symbol is on, in conjunction with the /µs symbol, the PX-7
DL is displaying a sound-velocity value in inches- per-microsecond.

When the M symbol is on, in conjunction with the /s symbol, the PX- 7
DL is displaying a sound-velocity value in meters-per-second.

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The Transducer

The transducer is the "business end" of the PX-7. It transmits and
receives ultrasonic sound waves that the PX-7 uses to calculate the
thickness of the material being mea sured. The transducer connects to the
PX-7 via the attached cable, and one coaxial connector.

The transducer must be used correctly in order for the PX-7 to produce
accurate, reliable measurements. Below is a short description of the

transducer, followed by instructions for its use.

The diagram above is a side view of a typical single element delay line
transducer. This delay line is fastened to the transducer with a retainer
ring. A drop of couplant is applied between the delay line and transducer
body. The transducer body contains one crystal element that is
responsible for conducting ultrasonic sound into and back from the material
being measured. When the transducer is placed against the material being
measured, it is the area directly beneath the delay line that is being
measured.

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When measuring, press against the top of the transducer with the
thumb or index finger to hold the transducer in place. Moderate pressure is
sufficient, as it is only necessary to keep the transducer stationary, and the
delay line seated flat against the surface of the material being measured.

Making Measurements

In order for the transducer to do its job, there must be no air gaps
between the wear-face and the surface of the material being measured.
This is accompli shed with the use of a "coupling" fluid, commonly called
"couplant". This fluid serves to "couple", or transfer, the ultrasonic sound
waves from the transducer, into the material, and back again. Before
attempting to make a measurement, a small amount of couplant should be
applied to the surface of the material being measured. Typically, a single
droplet of couplant is sufficient.

After applying couplant, press the transducer (wearface down) firmly
against the area to be measured. The Stability Indicator should have six or
seven bars darkened, and a number should appear in the display. If the
PX-7 has been set to the correct sound velocity (see page 13), the number
in the display will indicate the actual thickness of the material directly
beneath the transducer.

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If the Stability Indicator has fewer than five bars darkened, or the numbers
on the display seem erratic, first check to make sure that there is an
adequate film of couplant beneath the transducer, and that the transducer
is seated flat against the material. If the condition persists, it may be
necessary to select a different transducer (size or frequency) for the
material being measured. See page 28 for information on transducer
selection.

While the transducer is in contact with the material that is being
measured, the PX-7 will perform four measurements every second,
updating its display as it does so. When the transducer is removed from
the surface, the display will hold the last measurement made.

IMPORTANT

Occasionally, a small film of couplant will be drawn out between the
transducer and the surface as the transducer is removed. When this
happens, the PX-7 DL may perform a measurement through this couplant
film, resulting in a measurement that is larger or smaller than it should be.
This phenomenon is obvious when one thickness value is observed while
the transducer is in place, and another value is observed after the
transducer is removed.

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Condition and Preparation of Surfaces

In any ultrasonic measurement scenario, the shape and roughness of
the test surface are of paramount importance. Rough, uneven surfaces
may limit the penetration of ultrasound through the material, and result in
unstable, and therefore unreliable, measurements. The surface being
measured should be clean, and free of any small particulate matter, rust, or
scale. The presence of such obstructions will prevent the transducer from
seating properly against the surface. Often, a wire brush or scraper will be
helpful in cleaning surfaces. In more extreme cases, rotary sanders or
grinding wheels may be used, though care must be taken to prevent
surface gouging, which will inhibit proper transducer coupling.

Extremely rough surfaces, such as the pebble-like finish of some cast
iron, will prove most difficult to measure. These kinds of surfaces act on
the sound beam like frosted glass on light:, the beam becomes diffused
and scattered in all directions.

In addition to posing obstacl es to measurement, rough surfaces
contribute to excessive wear of the transducer, particularly in situations
where the transducer is "scrubbed" along the surface.

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Calibration

In order for the PX- 7 DL to make accurate measurements, it must be
set to the correct sound-velocity for the material being measured. Different
types of material 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 tool is not set to the correct sound-velocity, all of the measurements the
tool makes will be erroneous by some fixed percentage. The one point
calibration is the simplest and most commonly used calibration procedure -

optimizing linearity over large ranges. The PX-7 DL provides two simple
methods for setting the sound-velocity, described in the following pages.

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Calibration to a known thickness

NOTE: This procedure requires a sample piece of the specific

material to be measured, the exact thickness of which is known,
e.g. from having been measured by some other means.

1) Make sure the PX-7 DL is on.

2) Apply couplant to the sample piece.

3) Press the transducer against the sample piece, making sure that
the transducer sits flat against the surface of the sample. The
display should show some (probably incorrect) thickness value,
and the Stability Indicator should have nearly all its bars on.

4) Having achieved a stable reading, remove the transducer. If the
displayed thickness changes from the value shown while the
transducer was coupled, repeat step 3.

5) Press the CAL key. The IN (or MM ) symbol should begin flashing.

6) Use the UP and DOWN arrow keys to adjust the displayed
thickness up or down, until it matches the thickness of the sample
piece.

7) Press the CAL key again. The IN/µs (or M/s) symbols should
begin flashing. The PX-7 DL is now displaying the sound velocity

value it has calculated based on the thickness value that was
entered in step 6.

8) Press the CAL key once more to exit the calibration mode. The
PX-7 DL is now ready to perform measurements.

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Calibration to a known velocity

NOTE: This procedure requires that the operator know the sound-

velocity of the material to be measured. A table of common
materials and their sound-velocities can be found in Appendix C.

1) Make sure the PX-7 DL is on.

2) Press the CAL key to enter calibration mode. If the IN (or MM)
symbol is flashing, press the CAL key again, so that the IN/µs (or
M/s) symbols are flashing.

3) Use the UP and DOWN arrow keys to adjust the displayed velocity
up or down, until it matches the sound-velocity of the material to be
measured.

4) Press the CAL key once more to exit the calibration mode. The
PX-7 DL is now ready to perform measurements.

NOTE: At any time during the calibration procedure (IN, MM, IN/ µs, or

M/s flashing in the display), pressing the CLR key will restore the tool to the
factory default sound-velocity for steel (0.233 IN/ µs).

To achieve the most accurate measurements possible, it is generally
advisable to always calibrate the PX-7 DL to a sample piece of known
thickness. Material composition (and thus, its sound-velocity) sometimes
varies from lot to lot and from manufacturer to manufacturer. Calibration to
a sample of known thickness will ensure that the tool is set as closely as
possible to the sound velocity of the material to be measured.

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PX-7 DL Modes & Features

The Back light

The back light of the PX-7 DL can be set to three different positions
on/off/auto. The following steps outline the procedure for changing the
settings of the back light:

1) Press ON/OFF key to power up the PX-7 DL.

1) Press the MODE key to activate features and settings.

2) Press the UP / Down arrow keys to scroll to the LItE symbol.

3) Press the SEND key to toggle the status of the back light
on/off/auto.

4) Press the MODE key once again to return to measurement mode.

Scan Mode

While the PX-7 DL excels at making single point measurements, it is

sometimes desirable to examine a larger region, searching for the thinnest
point. The PX-7 DL includes a feature, called Scan Mode, which allows it

to do just that.

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In normal operation, the PX-7 DL performs and displays four
measurements every second, which is quite adequate for single
measurements. In Scan Mode, however, the tool performs eight
measurements every second, but does not display them. While the

transducer is in contact with the material being measured, the PX-7 DL is
keeping track of the lowest measurement it finds. The transducer may be
"scrubbed" across a surface, and any brief interruptions in the signal will be
ignored. When the transducer loses contact with the surface for more than
a second, the PX-7 DL will display the smallest measurement it found.

When the PX-7 DL is in measurement mode, press the MODE key to
activate the features and settings. The display will begin flashing ALAr
(alarm), followed by the status - on/off. Use the UP and DOWN arrow keys
to scroll to SCAn mode. Press the SEND key to toggle scan mode on/off.
While scanning, the display will show a moving series of dashes instead of
a thickness value. When the transducer is removed from the material

being scanned, the PX-7 DL will (after a brief pause) display the smallest
measurement it found.

Alarm Mode

The Alarm Mode feature of the PX-7 DL allows the user to set an
audible and visual parameter when taking measurements. If the
measurement falls below a nominal value, set by the user, a red light will
be illuminated on the front panel of the gauge and the beeper sounded.
This improves the speed and efficiency of the inspection process by
eliminating constant viewing of the actual reading displayed. The following
procedures outline how to enable and set up this feature:

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Using the Beeper

1) Press ON/OFF key to power up the unit.

2) Press MODE key to activate features and settings.

3) Press the UP or DOWN arrow keys to scroll to bEEP.

4) Press the SEND key to toggle the status of the beeper on/off.

5) Press the MODE key once again to return to measurement mo de.

Alarm Mode

1) Press ON/OFF key to power up the PX-7 DL.

2) Press the MODE key to activate features and settings.

3) Mode will start with ALAr feature and current status.

4) Press send key to toggle ALAr status on/off.

5) Status ON - A nominal value will be displayed with the units IN/MM
flashing.

6) Press the UP or DOWN arrow keys to scroll to the desired nominal
thickness value.

7) Press the SEND key to select the desired nominal value and return
to mode menu.

8) Press the MODE key once again to return to measurement mode.

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Measurement Modes

The PX-7 is equipped with three measurement mode options (echo­echo, interface- echo, or auto). In echo-echo mode, the gauge has the
ability to read thin metals down to .006 inches (.15 millimeters). The echo­echo mode also allows the user to measure the thickness of metals that
have been previously coated or painted on the surface. This enables the
user to determine the thickness of the metal without having to remove the
paint. In interface-echo mode, the gauge has the ability to read plastics
and thicker materials. The PX-7's auto mode will automatically switch
between modes according to the different materials being measured.
Finally, the plas mod can be used to measure thin plastics using a special
graphite tip. The following section outlines how to switch between
measurement modes:

Measurement Modes

1) Press ON/OFF key to power up the PX-7 DL.

2) Press the MODE key to activate features and settings.

3) Press the UP or DOWN arrow keys to scroll to GAtE.

4) Press the SEND key to toggle between the different measurement
modes ( E-E, I-E, AutO, and PLAS ).

5) Press the MODE key once again to return to measurement mode.

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Differential Mode

In the Quality Control environment, it is sometimes necessary to know
the difference between a nominal (target) thickness value and an actual
thickness value. This feature is also included in the PX-7 DL. With the
Differential Mode enabled, the PX-7 DL will display the positive or negative
difference from an entered nominal value. The following steps ou tline the
procedure for setting up this feature:

Differential Mode

6) Press ON/OFF key to power up the PX-7 DL.

7) Press the MODE key to activate features and settings.

8) Press the UP or DOWN arrow keys to scroll to dIFF.

9) Press the SEND key to toggle the staus of the differential mode
on/off.

10)Status ON - A nominal value will be displayed with the units IN/MM
flashing.

11)Press the UP or DOWN arrow keys to scroll to the desired nominal
thickness value.

12)Press the SEND key to select the desired nominal value and return
to mode menu.

13)Press the MODE key once again to return to measurement mode.

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RS232 Serial Port & The Data Logger

The PX-7 DL is equipped with an RS232 serial port. Using the
accessory cable (part# N-306-0010), the PX-7 DL has the ability to connect
to a computer, or external storage device. The following section outlines
the procedure for connecting the PX-7 DL to a computer, and how to collect
data using any standard communications program:

Connecting To a Computer

1) Connect the accessory cable (part# N-306- 0010) to the 2 pin jack
located on the bottom of the PX-7 DL, and the 9 pin connector to a
serial port on the computer.

2) Start the communications software that will be used to collect the
measurements (i.e. Dakota Ultrasonics DakView, Microsoft
Windows 3.1 - Terminal, or 95/98 - HyperTerminal).

3) Setup the communications software using the following
parameters: Data Bits - 8, Parity - None, Stop Bits - 1, Baud
Rate 1200 (to print a report), or 9600 to transfer data file.

§ Note: Step 3 is not required when Using DakView software.

§ Note: A report can be printed to a communications program (i.e.

HyperTerminal), or printed to a serial printer using 8.5" x 11" paper.

4) Set the communications software COMM port to the port number
that the PX-7 DL is connected - direct comm1, comm 2, etc.

5) Proceed to the section USING THE DATA LOGGER .

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Note: Communications software packages generally have the ability

to capture the screen data to a common text file. This text file,
containing the measurements, can then be imported into any
common spreadsheet program (i.e. Excel , Quattro Pro,
Lotus123) for further reporting requirements.

Using The Data Logger

The PX-7 DL is equipped with an on board data logging feature.

This will prove to be a valuable reporting tool for inspection
purposes. It will increase efficiency by reducing the time it takes to
manually record the measurements during the inspection process.

The PX-7 DL can then be connected to a computer or serial printer
to save and print the results of the inspect ion.

The PX-7 DL has a storage capacity of 1000 measurements.

The PX-7 DL has 10 files consisting of 100 sequential storage
locations in each file. The procedure for using the data logger is
outlined in the following steps:

1) Press ON/OFF key to power up the PX- 7 DL.

2) Press the MEM key to activate the data logger.

§ Note: The display will flash FILE / F-01 (or the last file used)

symbol. Remember, there are 10 files F-01 thru F- 10.

3) Press the SEND key to enter file setup.

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Using the Data Logger (con't)

• The cu rrent file will be diplayed ( F-01, F-03, etc. )

4) Press the UP / DOWN arrow keys to scroll to the file ( 1- 10 ) that

will be used to record the measurements.

5) Press the SEND key once again to select the file.

• Note: The display will flash the FILE / F-04 ( The selected file

)symbol.

6) Press the MEM key, once again, to advance to the storage

locations in the file selected.

• Note: The display will flash the current storage location ( L007,

L039, etc. ), followed by the status of the location. The storage
location can contain one of three possible things: a) a
measurement that was previously stored. b) A clear location,
indicated by the CLr symbol. c) Obstruct ( ObSt ), indicating that a
measurement could not be obtained.

7) Press the UP / DOWN arrow keys to adv ance to the desired cell

location.

8) Take a measurement and press the SEND key to store a reading in

the desired location.

• The data logger will automatically advance to the next storage

location in sequential order.

9) Repeat step 8 as required.

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Clearing a Storage Location

The user may require a storage location, that is currently full, be over
written. This procedure is outlined in the following steps:

• Note: Assuming the steps in Using The Data Logger have been

completed, and step 8 is being repeated.

1) Press the UP / DOWN arrow keys to move to the location to be

over written.

• Note: If the user attempts to write to a location that is currently full,

the display will flash the FuLL symbol.

2) Press the CLR key to delete the contents of the storage location.

The display will flash the storage location ( L011, L099, etc. ) and
the CLr symbol.

3) Take another measurement, and press the SEND key to write to

the same storage location just cleared.

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Clearing an Entire File

The user may require the contents of an entire file be completely
cleared of all measurements. This would allow the user to start a new
list of measurements starting at storage location L001. The procedure
is outlined in the following steps:

1) Press the ON/OFF key to power up the PX-7 DL.

2) Press the MEM key to activate the data logging functions and

settings.

3) Press the SEND key to enter file setup.

4) Press the UP / DOWN arrow keys to scroll to the file that will be

cleared of all measurements.

5) Press the SEND key once again to select the file.

• Note: The display will flash the FILE / F-05 ( The file selected by

the user ) symbol.

6) Press the UP / DOWN arrow keys to scroll to the flashing CLr / F-

05 ( The file selected by the user ) symbol.

7) Press the SEND key to select the clear file option. The symbol (

CLr? ) will be displayed.

8) Press the CLR key to confirm and clear the contents of the entire

file.

9) Press the MEM key, at any time, to exit the data logging functions

and return to measurement mode.

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Clearing all Files

1) Press the ON/OFF key to power up the PX-7 DL.

2) Immediately press the CLR key. CLr? Will be displayed.

3) Press the CLR key once again to clear all files.

Sending All Files to a Computer

At the end of the inspection process, or end of the day, the user may
require the readings be transferred to a computer. The following steps
outline this procedure:

1) Refer to the section on Connecting to a Computer, page 21,

before proceeding.

2) Press the ON/OFF key to power up the PX-7 DL.

3) Press the MEM key to activate the data log ging functions and

settings.

4) Press the UP / DOWN arrow keys to scroll to the SEnd / ALL

symbol flashing on the display.

5) Press the SEND key to send all data files to the computer.

5) Press the MEM key to exit the data logging functions and return to

measurement mode.

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Printing a File

The user may wish to print an individual file to a serial printer or
computer. A file can, very simply, be printed to a communications
program on a PC ( i.e. Dakota Ultrasonics DakView, Windows 3.1 ­Terminal, Window 95/98 - HyperTerminal ), and then printed. The
procedure for printing a file is outlined below:

1) Refer to the section on Connecting to a Computer, page 21,

before proceeding.

2) Press the ON/OFF key to power up the PX-7 DL.

3) Press the MEM key to activate the data logging functions and

settings.

4) Press the SEND key to enter file setup.

5) Press the UP / DOWN arrow keys to scroll to the file to be printed (

F-01, F-05, etc. ).

6) Press SEND, once again, to select the file to be printed. The display

will flash the FILE / F-05 ( The file selected ) symbol.

7) Press the UP / DOWN arrow keys to scroll to the flashing Prnt / F-

05 ( The file chosen ), or LISt (tape printer) symbol.

8) Press the SEND key to print the contents of the file.

9) Press the MEM key, at any time, to exit the data logging functions

and return to measurement mode.

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TRANSDUCER SELECTION

The PX-7 is inherently capable of performing measurements on a wide
range of materials, from various metals to glass and plastics. Different
types of material, however, will require the use of different transducers.
Choosing the correct transducer for a job is critical to being able to easily
perform accurate and reliable measurements. The following paragraphs
highlight the important properties of transducers, which should be
considered when selecting a transducer for a specific job.

Generally speaking, the best transducer for a job is one that sends
sufficient ultrasonic energy into the material being measured such that a
strong, stable echo is received by the PX-7. Several factors affect the
strength of ultrasound as it travels. These are outlined below:

• Initial Signal Strength

The stronger a signal is to begin with, the stronger its return echo
will be. Initial signal strength is largely a factor of the size of the
ultrasound emitter in the transducer. A large emitting area will send
more energy into the material being measured than a small emitting
area. Thus, a so-called "1/4-inch" transducer will emit a stronger signal
than a "1/8-inch" transducer.

• Absorption and Scattering
As ultrasound travels through any material, it is partly absorbed. If

the material through which the sound travels has any grain structure,
the sound waves will experience scattering. Both of these effect s

PX-7 DL Ultrasonic Thickness Gauge

29

reduce the strength of the waves, and thus, the PX-7's ability to detect
the returning echo.

Higher frequency ultrasound is absorbed and scattered more than

ultrasound of a lower frequency. While it may seem that using a lower
frequency transducer might be better in every instance, low frequencies
are less directional than high frequencies.

• Geometry of the Transducer
The physical constraints of the measuring environment sometimes

determine a transducer's suitability for a given job. Some transducers
may simply be too large to be used in tightly confined areas. Also, the
surface area available for contacting with the transducer may be limited,
requiring the use of a transducer with a small cone tipped delay line.
Measuring on a curved surface, may require the use of a transducer
with a matching curved wearface.

• Temperature of the Material
When it is necessary to measure on surfaces that are exceedingly

hot, special delay lines may be neccessary. Additionally, care must be
taken when performing a "Calibration to Known Thickness" with a high
temperature application. See Appendix B for more information on
measuring materials with a high temperatures.

Selection of the proper transducer is often a matter of tradeoffs between
various characteristics. It may be necessary to experiment with a variety of
transducers in order to find one that works well for a given job. Dakota
Ultrasonics can provide assistance in choosing a transducer, and offers a
broad selection of transducers for evaluation in specialized applications.

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31

Physical

Weight: 10 ounces(with batteries).
Size: 2.5W x 4.5 H x 1.24 D inches
(63.5W x 114.3 H x 31.5 D mm).
Operating Temperature: -20 to 120 °F ( -30 to 50 °C)
Case: Extruded aluminum body / nickel plated aluminum end
caps.

PX-7 DL Ultrasonic Thickness Gauge

APPENDIX A

Product Specifications

Keypad

Sealed membrane, resistant to water and petroleum products.

Power Source

Two “AA” size, 1.5 volt alkaline or 1.2 volt NiCad cells. 150 hours
typical operating time on alkaline, 100 hours on NiCad.

Display

Liquid-Crystal-Display, 4.5 digits, 0.500 inch high numerals. LED
backlight.

Measuring

Range: 0.0060 to 1.0000 inches (0.15 to 25.40 millimeters) - Steel
Resolution: 0.0001 inch (0.001 millimeter)
Accuracy: ±0.0001 inch (0.001 millimeter), depends on material

and conditions

Sound Velocity Range: 0.0492 to 0.3937 in/µs (1250 to 10000m/s)

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PX-7 DL Ultrasonic Thickness Gauge

33

APPENDIX B

Application Notes

• Measuring tubing

When measuring a piece of tubing for wall thickness, it may prove
beneficial to have multiple delay lines with different radiuses for different
tubing diameters. The delay lines can be easily radiused by placing a
piece of emery cloth around the tubing and moving the transducer back
and forth until a radius has formed on the tip of the delay line.

• Measuring hot surfaces

The velocity of sound through a substance is dependant upon its
temperature. As materials heat up, the velocity of sound through them
decreases. In most applications with surface temperatures less than about
200°F (100 °C), no special procedures must be observed. At temperatures
above this point, the change in sound velocity of the material being
measured starts to have a noticeable effect upon ultrasonic measurement.

At such elevated temperatures, it is recommended that the user perform
a calibration procedure (refer to page 13) on a sample piece of known
thickness, which is at or near the temperature of the material to be
measured. This will allow the PX-7 to correctly calculate the velocity of
sound through the hot material.

When performing measurements on hot surfaces, it may also be
necessary to use a specially constructed high -temperature delay line. It is
recommended that the probe be left in contact with the surface for as short

Dakota Ultrasonics

34

a time as needed to acquire a stable measurement. While the transducer
is in contact with a hot surface, it will begin to heat up, and through thermal
expansion and other effects, may begin to adversely affect the accuracy of
measurements.

• Measuring laminated materials

Laminated materials are unique in that their density (and therefore
sound-velocity) may vary considerably from one piece to another. Some
laminated materials may even exhibit noticeable changes in sound-velocity
across a single surface. The only way to reliably measure such materials is
by performing a calibration procedure on a sample piece of known
thickness. Ideally, this sample material should be a part of the same piece
being measured, or at least from the same lamination batch. By calibrating
to each test piece individually, the effects of variation of sound-velocity will
be minimized.

An additional important consideration when measuring laminates, is that
any included air gaps or pockets will cause an early reflection of the
ultrasound beam. This effect will be noticed as a sudden decrease in
thickness in an otherwise regular surface. While this may impede accurate
measurement of total material thickness, it does provide the user with
positive indica tion of air gaps in the laminate.

PX-7 DL Ultrasonic Thickness Gauge

35

in/us

m/s

Aluminum

0.250

6350

Brass

0.173

4394

Cast Iron

0.180

(apprx)

4572

Copper

0.184

4674

Epoxy resin

0.100

(apprx)

2540

Glass, crown

0.223

5664

Gold

0.128

3251

Iron

0.232

5893

Magnesium

0.228

5791

Nylon

0.102

(apprx)

2591

Platinum

0.156

3962

Polystyrene

0.092

2337

PVC

0.094

2388

Rubber, vulcanized

0.091

2311

Silver

0.142

3607

Steel, stainless

0.223

5664

Teflon

0.056

1422

Titanium

0.240

6096

Zinc

0.166

4216

APPENDIX C

Sound Velocities of some Common Materials

Material sound velocity

Bismuth 0.086 2184
Cadmium 0.109 2769
Constantan 0.206 5232

German silver 0.187 4750
Glass,flint 0.168 4267
Ice 0.157 3988
Lead 0.085 2159
Mercury 0.057 1448

Nickel 0.222 5639
Paraffin 0.087 2210
Plexiglass 0.106 2692
Porcelain 0.230 (apprx) 5842
Quartz glass 0.222 5639

Steel, common 0.233 5918
Stellite 0.275 (apprx) 6985
Tin 0.131 3327
Tungsten 0.210 5334
Water 0.058 1473

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PX-7 DL Ultrasonic Thickness Gauge

37

WARRANTY INFORMATION

• Warranty Statement •

Dakota Ultrasonics warrants the PX-7 DL against defects in materials and
workmanship for a period of five years from receipt by the end user. Additionally,
Dakota Ultrasonics warrants transducers and accessories against such defects for a
period of 90 days from receipt by the end user. If Dakota Ultrasonics receives notice of
such defects during the warranty period, Dakota Ultrasonics will either, at its option,
repair or replace products that prove to be defective.

Should Dakota Ultrasonics be unable to repair or replace the product within a
reasonable amount of time, the customer's alternative exclusive remedy shall be refund
of the purchase price upon return of the product.

• Exclusions •

The above warranty shall not apply to defects resulting from: improper or
inadequate maintenance by the customer; unauthorized modification or misuse; or
operation outside the environmental specifications for the product.

Dakota Ultrasonics makes no other warranty, either express or implied, with respect
to this product. Dakota Ultrasonics specifically disclaims any implied warranties of
merchantability or fitness for a particular purpose. Some states or provinces do not
allow limitations on the duration of an implied warranty, so the above limitation or
exclusion may not apply to you. However, any implied warranty of merchantability or
fitness is limited to the five-year duration of this written warranty.

This warranty gives you specific legal rights, and you may also have other rights
which may vary from state to state or province to province.

• Obtaining Service During Warranty Period •

If your hardware should fail during the warranty period, contact Dakota Ultrasonics
and arrange for servicing of the product. Retain proof of purchase in order to obtain
warranty service.

For products that require servicing, Dakota Ultrasonics may use one of the following
methods:

- Repair the product

- Replace the product with a re-manufactured unit

- Replace the product with a product of equal or greater performance

- Refund the purchase price.

• After the Warranty Period •

If your hardware should fail after the warranty period, contact Dakota Ultrasonics for
details of the services available, and to arrange for non-warranty service.

MATERIAL SAFETY DATA SHEET

N/A = not applicable or not available (To comply with 29 CFR 1910.1200)

SECTION 1 – PRODUCT IDENTIFICATION

Product Name: SOUNDSAFE
Generic Name: Ultrasonic Couplant
Manufacturer: Sonotech, Inc.
774 Marine Dr., Bellingham, WA 98225
[phone]

SECTION 2 – HAZARDOUS INGREDIENTS

This material does not contain any ingredients having

known health hazards in concentrations greater than 1%.

This material does not contain any known or suspected

carcinogens.

SECTION 4 – FIRE AND EXPLOSION

HAZARD DATA

Flash Point : none
Upper Exposure Limit: none
Lower Exposure Limit: none
Special Fire Fighting Procedures : N/A
Extinguishing media: N/A
Unusual Fire and Explosion Hazards : none

NFPA Hazardous Materials

Identification System (est)

Health……………………0
Flammability…………….0
Reactivity………………..0

SECTION 3 – PHYSICAL DATA

(nominal)

Boiling Point: >220 °F pH: 7.35 – 7.9
Freezing Point: <20°F Acoustic Imp.: 1.726x10
Vapor Pressure: N/A Vapor Density: N/A
Evaporation Rate: N/A Specific Gravity: >1.02
Solubility in Water: complete
Appearance and Odor: water white, opaque gel;
bland odor

6

SECTION 5 – REACTIVITY DATA

Stability: Stable
Conditions to Avoid: none
Incompatibility (Materials to Avoid): none known
Hazardous Polymerization: will not occur
Hazardous Decomposition or Byproducts: none known

SECTION 6 – HEALTH HAZARD AND FIRST AID DATA

Routes of Entry :
Skin: not likely Ingestion: not normally
Eyes: not normally Inhalation: no
Effects of Overexposure: Acute: May cause temporary

1

eye irritation

Chronic: none expected

SECTION 7 – STORAGE AND HANDLING

INFORMATION

Precautions to be taken in handling and storage: Store
between 20°F and 120 °F. Spills are slippery and should

be cleaned up immediately.
Steps to be taken in case material is released or spilled:
Pick up excess for disposal. Clean with water.
Waste disposal method: Dispose of in accordance with
federal, state, and local regulations.

1

SOUNDSAFE contains only food grade and cosmetic grade ingredients.

SONOTECH, INC.

Toll Free: 1-800-458-4254

774 Marine Dr., Bellingham, WA 98225

Telephone: [phone]

First Aid Procedures :
Skin: Remove with water if desired.
Eyes: Flush with water for 15 minutes.
Ingestion: For large quantities, induce vomiting and

call a physician.

Inhalation: N/A

SECTION 8 – CONTROL MEASURES

Respiratory Protection: not required
Ventilation: not required
Protective Gloves : on individuals demonstrating

sensitivity to SOUNDSAFE
Eye Protection: as required by working conditions
Other Protective Equipment : not required

Fax: [phone]