Aktek AT300 User manual

Reliable Measurement and Control
ULTRASONIC THICKNESS
GAUGE
AT300
USER MANUAL

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1 Overview................................................................................................3
1.1 Product Specifications................................................................3
1.2 Main Functions.............................................................................3
1.3 Measuring Principle.....................................................................3
1.4 Configuration................................................................................4
1.5 Operating Conditions..................................................................4
2 Structure Feature................................................................................. 4
2.1 Measurement Screen .................................................................5
2.2 Keypad Definitions ......................................................................5
3 Preparation............................................................................................5
3.1 Transducer Selection..................................................................5
3.2 Condition and Preparation of Surfaces....................................7
4 Operation...............................................................................................8
4.1 Power On/Off................................................................................8
4.2 Probe Zero....................................................................................8
4.3 Sound Velocity Calibration.........................................................9
4.4 Making Measurements.............................................................10
4.5 Scan mode.................................................................................. 11
4.6 Changing Resolution................................................................. 11
4.7 Changing Units ..........................................................................12
4.8 Memory Management...............................................................12
4.9 Data Printing...............................................................................13
4.10 Beep Mode...............................................................................13
4.11 EL Backlight..............................................................................13
4.12 Battery Information..................................................................13
4.13 Auto Power Off.........................................................................13
4.14 System Reset...........................................................................13
4.15 Connecting to a Computer.....................................................13
5 Servicing..............................................................................................14
6 Transport and Storage.......................................................................14
Appendix A Sound Velocities...............................................................14
Appendix B Applications Notes...........................................................15

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1 Overview
The model AT300 is a digital ultrasonic thickness gauge. Based on the same operating
principles as SONAR, the instrument is capable of measuring the thickness of various
materials with accuracy as high as 0.1/0.01 millimeters. It is suitable for a variety of metallic
and non-metallic materials.
1.1 Product Specifications
1) Display：4.5 digits LCD with EL backlight.
2) Measuring Range：0.75～300mm (in Steel).
3) Sound Velocity Range: 1000~9999 m/s.
4) Resolution：AT300: 0.1/0.01mm
5) Accuracy：±（0.5%Thickness+0.04）mm, depends on materials and conditions
6) Units: Metric/Imperial unit selectable.
7) Four measurements readings per second for single point measurement, and ten per
second for Scan Mode.
8) Memory for up to 20 files (up to 99 values for each file) of stored values.
9) Power Source：Two “AA” size, 1.5 Volt alkaline batteries. 100 hours typical operating
time (EL backlight off).
10) Communication：RS232 serial port for MAT300.
11) Outline dimensions：150×74×32 mm.
12) Weight：245g
1.2 Main Functions
1) Capable of performing measurements on a wide range of material, including metals,
plastic, ceramics, composites, epoxies, glass and other ultrasonic wave well-conductive
materials.
2) Transducer models are available for special application, including for coarse grain
material and high temperature applications.
3) Probe-Zero function, Sound-Velocity-Calibration function
4) Two-Point Calibration function.
5) Two work modes: Single point mode and Scan mode.
6) Coupling status indicator showing the coupling status.
7) Battery information indicates the rest capacity of the battery.
8) Auto sleep and auto power off function to conserve battery life.
9) Optional software to process the memory data on the PC forAT300
10) Optional thermal mini-printer to print the measured data via RS232 port forAT300
1.3 Measuring Principle
The digital ultrasonic thickness gauge determines the thickness of a part or structure by
accurately measuring the time required for a short ultrasonic pulse generated by a
transducer to travel through the thickness of the material, reflect from the back or inside
surface, and be returned to the transducer. The measured two-way transit time is divided by
two to account for the down-and-back travel path, and then multiplied by the velocity of
sound in the material.

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The result is expressed in the well-known relationship:
2
tv
H

Where：H－Thickness of the test piece.
v－Sound Velocity in the material.
t－The measured round-trip transit time.
1.4 Configuration
Table 1-1
No
.
Item
Quantity
Note
Standard
Configur
ation
1
Main body
1
2
Transducer
1
Model:
N05/90°
3
Couplant
1
4
Instrument Case
1
5
Operating Manual
1
6
Alkaline battery
2
AA size
7
8
Optional
Configur
ation
9
Transducer: N02
See
Table3-1
10
Transducer: N07
11
Transducer: HT5
12
Mini thermal
printer
1
Only for
AT300
13
Print cable
1
14
DataPro Software
1
15
Communication
Cable
1
1.5 Operating Conditions
Operating Temperature: －20～＋60℃;
Storage Temperature：-30℃～＋70℃
Relative Humidity ≤90％；
The surrounding environment should avoid of vibration, strong magnetic field, corrosive
medium and heavy dust.
2 Structure Feature
POWER: 2 X 1.5V
SN:
ULTRASONIC
THICKNESS GAUGE

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1 The main body 2 Keypad 3 LCD display 4 Pulser socket 5 Receiver socket 6 Probe
zero disc 7 Communication port 8 Label 9 Battery cover 10 Probe
2.1 Main Screen
1, Coupling Status: Indicate the coupling status. While the gauge is taking a measurement,
the coupling status should be on. If it is not on or not stable, the gauge is having difficulty
achieving a stable measurement, and the thickness value displayed will most likely be
erroneous.
2, Unit: Current unit system. MM or IN for thickness value. M/S or IN/μS for sound velocity.
3, Battery Information: Display the rest capacity of the battery.
4, Information Display: Displays the measured thickness value, the sound velocity and
shows hints of current operation.
2.2 Keypad Definitions
Turn the instrument
on/off
Sound velocity
calibration
Turn on/off the EL
backlight
Enter
Probe-Zero
operation
Plus;
Turn on/off Scan
mode
Unit switch between
Metric and Imperial
system
Minus;
Turn on/off the
beep mode
Data Save or Data
Delete
3 Preparation
3.1 Transducer Selection
The gauge 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 measurement. 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

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energy into the material being measured such that a strong, stable echo is received by the
gauge. 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 “1/2 inch” transducer will emit a stronger signal
than a “1/4 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 effects reduce the strength of the waves,
and thus, the gauge’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. Thus, a higher frequency transducer would be a
better choice for detecting the exact location of small pits or flaws in the material being
measured.
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
wearface. Measuring on a curved surface, such as an engine cylinder wall, 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, high temperature transducers must be used. These transducers are built
using special materials and techniques that allow them to withstand high temperatures
without damage. Additionally, care must be taken when performing a “Probe-Zero” or
“Calibration to Known Thickness” with a high temperature transducer.
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.
The transducer is the “business end” of the instrument. It transmits and receives
ultrasonic sound waves that the instrument uses to calculate the thickness of the material
being measured. The transducer connects to the instrument via the attached cable, and two
coaxial connectors. When using transducers, the orientation of the dual coaxial connectors
is not critical: either plug may be fitted to either socket in the instrument.
The transducer must be used correctly in order for the instrument to produce accurate,
reliable measurements. Below is a short description of the transducer, followed by
instructions for its use.
Left figure is a bottom view of a typical transducer. The two semicircles of the wearface

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are visible, as is the barrier separating them. One of the semicircles is responsible for
conducting ultrasonic sound into the material being measured, and the other semicircle is
responsible for conducting the echoed sound back into the transducer. When the transducer
is placed against the material being measured, it is the area directly beneath the center of
the wearface that is being measured.
Right figure is a top view of a typical transducer. Press against the top 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 wearface seated flat against the
surface of the material being measured.
Table 3-1 Transducer Selection
Model
Freq
MHZ
Diam
mm
Measuring
Range
Lower
limit
Description
N02
2.5
14
3.0mm～
300.0mm（In
Steel）
40mm (in
Gray Cast
Iron HT200)
20
for thick, highly
attenuating, or
highly scattering
materials
N05
5
10
1.2mm～
230.0mm（In
Steel）
Φ20mm
×3.0mm
Normal
Measurement
N05
/90°
5
10
1.2mm～
230.0mm（In
Steel）
Φ20mm
×3.0mm
Normal
Measurement
N07
7
6
0.75mm～
80.0mm
（In Steel）
Φ15mm
×2.0mm
For thin pipe wall
or small
curvature pipe
wall
measurement
HT5
5
14
3～200mm
（In Steel）
30
For high
temperature
(lower than
300℃)
measurement.
3.2 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 obstacles to measurement, rough surfaces contribute to excessive

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wear of the transducer, particularly in situations where the transducer is “scrubbed” along
the surface. Transducers should be inspected on a regular basis, for signs of uneven wear
of the wearface. If the wearface is worn on one side more than another, the sound beam
penetrating the test material may no longer be perpendicular to the material surface. In this
case, it will be difficult to exactly locate tiny irregularities in the material being measured, as
the focus of the sound beam no longer lies directly beneath the transducer.
4 Operation
4.1 Power On/Off
The instrument is turned on by pressing the key.
The gauge can be turned off by pressing the key while it is on. The tool has a
special memory that retains all of its settings even when the power is off.
4.2 Probe Zero
The key is used to “zero” the instrument in much the same way that a mechanical
micrometer is zeroed. If the gauge is not zeroed correctly, all the measurements that the
gauge makes may be in error by some fixed value. When the instrument is “zeroed”, this
fixed error value is measured and automatically corrected for all subsequent measurements.
The instrument may be “zeroed ” by performing the following procedure.:
1) Plug the transducer into the instrument. Make sure that the connectors are fully
engaged. Check that the wearface of the transducer is clean and free of any debris.
2) Press the key to activate the probe zero mode.
3) Use the key and the key to scroll to the probe model currently being used. Be
sure to set the right probe model to the instrument. Otherwise, there will be erroneous.
4) Apply a single droplet of ultrasonic couplant to the face of the metal probe-disc.
5) Press the transducer against the probe disc, making sure that the transducer sits flat
against the surface.
6) Remove the transducer from the probe disc.
At this point, the instrument has successfully calculated its internal error factor, and will
compensate for this value in any subsequent measurements. When performing a “probe
zero”, the instrument will always use the sound velocity value of the built-in probe-disc, even
if some other velocity value has been entered for making actual measurements. Though the
instrument will remember the last “probe zero” performed, it is generally a good idea to
perform a “probe zero” whenever the gauge is turned on, as well as any time a different
transducer is used. This will ensure that the instrument is always correctly zeroed.
Press while in probe zero mode will stop current probe zero operation and return to
the measurement mode.

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4.3 Sound Velocity Calibration
In order for the gauge 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. 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 procedure
optimizing linearity over large ranges. The Two-point calibration allows for greater accuracy
over small ranges by calculating the probe zero and velocity.
Note: One and Two point calibrations must be performed on material with the paint or
coating removed. Failure to remove the paint or coating prior to calibration will result in a
multi material velocity calculation that may be different from the actual material velocity
intended to be measured.
4.3.1 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) Perform a Probe-Zero.
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 thickness value, and
the coupling status indicator should appear steadily.
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 key to activate the calibration mode. The MM (or IN) symbol should begin
flashing.
6) Use the key and the key to adjust the displayed thickness up or down, until it
matches the thickness of the sample piece.
7) Press the key again. The M/S (or IN/μS) symbols should begin flashing. The gauge
is now displaying the sound velocity value it has calculated based on the thickness
value that was entered.
8) Press the key once again to exit the calibration mode and return to the
measurement mode. The gauge is now ready to perform measurements.
4.3.2 Calibration to a known velocity
Note: This procedure requires that the operator knows the sound velocity of the material to
be measured. A table of common materials and their sound velocities can be found in
Appendix A of this manual.
1) Press the key to activate the calibration mode. The MM (or IN) symbol should begin
flashing.
2) Press the key again, so that The M/S (or IN/μS) symbols are flashing.
3) Use the key and the key to adjust the sound velocity value up or down, until it
matches the sound velocity of the material to be measured. You can also press the
key to switch among the preset commonly using velocities.
4) Press the key to exit from the calibration mode. The gauge is now ready to perform

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measurements.
To achieve the most accurate measurements possible, it is generally advisable to
always calibrate the gauge 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 gauge is set
as closely as possible to the sound velocity of the material to be measured.
4.3.3 Two Point Calibration
Note: This procedure requires that the operator has two known thickness points on the test
piece that are representative of the range to be measured.
1) Perform a Probe-Zero.
2) Apply couplant to the sample piece.
3) Press the transducer against the sample piece, at the first/second calibration point,
making sure that the transducer sits flat against the surface of the sample. The display
should show some (probably incorrect) thickness value, and the coupling status
indicator should appear steadily.
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 key. The MM (or IN) symbol should begin flashing.
6) Use the key and the key to adjust the displayed thickness up or down, until it
matches the thickness of the sample piece.
7) Press the key. The display will flash 1OF2. Repeat steps 3 through 6 on the second
calibration point.
8) Press the key, so that The M/S (or IN/μS) symbols are flashing. The gauge will now
display the sound velocity value it has calculated based on the thickness values that
were entered in step 6.
9) Press the key once more to exit the calibration mode. The gauge is now ready to
perform measurements within this range.
4.4 Making Measurements
When the tool is displaying thickness measurements, the display will hold the last value
measured, until a new measurement is made.
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 accomplished 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 coupling status indicator should appear, and a digit number should
appear in the display. If the instrument has been properly “zeroed” and set to the correct
sound velocity, the number in the display will indicate the actual thickness of the material
directly beneath the transducer.
If the coupling status indicator does not appear, not stable, or the numbers on the
display seem erratic, firstly check to make sure that there is an adequate film of couplant

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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.
While the transducer is in contact with the material that is being measured, the
instrument 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.
Note：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 gauge 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. In
addition, measurements through very thick paint or coatings may result in the paint or
coating being measured rather than the actual material intended. The responsibility for
proper use of the instrument, and recognition of these types of phenomenon, rests solely
with the user of the instrument.
4.5 Scan mode
While the gauge excels at making single point measurements, it is sometimes desirable
to examine a larger region, searching for the thinnest point. The gauge includes a feature,
called Scan Mode, which allows it to do just that.
In normal operation, the gauge performs and displays four measurements every
second, which is quite adequate for single measurements. In Scan Mode, however, the
gauge performs ten measurements every second, and displays the readings while scanning.
While the transducer is in contact with the material being measured, the gauge 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 two seconds, the gauge will display the smallest
measurement it found. When the transducer is removed from the material being scanned,
the gauge will display the smallest measurement it found.
When the scan mode is turned off, the single point mode will be automatically turned on.
Turn on/off the scan mode by the following steps:
Press the key to switch the scan measurement mode on and off. It will display the
current condition of the scan mode on the main screen.
4.6 Changing Resolution
AT300 has selectable display resolution, which is 0.1mm and 0.01mm. This function is
not available for other models, which is fixed to 0.1mm.
Press down the key while turning on the gauge will switch the resolution between
“High” and “Low”.

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4.7 Changing Units
On the measurement mode, press the key to switch back and forth between
imperial and metric units.
4.8 Memory Management
4.8.1 Storing a reading
There are twenty files (F00-F19) that can be used to store the measurement values
inside the gauge. At most 100 records (thickness values) can be stored to each file. By
simply pressing the key after a new measurement reading appears, the measured
thickness value will be saved to current file. It is added as the last record of the file. To
change the destination file to store the measured values, follow the steps:
1) Press the key to activate the data logging functions. It will display the current file
name and the total record count of the file.
2) Use the key and the key to select the desired file to set as current file.
3) Press the key to exit the data logging functions at any time.
4.8.2 Clearing selected 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 L00. The procedure is outlined in the following steps.
1. Press the key to activate the data logging fuctions. It will display the current file
name and the total record count of the file.
2. Use the key and the key to scroll to the file that will be cleared of all
measurements.
3. Press the key on the desired file. It will automatically clear the file, and display
“-DEL”.
4. Press the key, at any time, to exit the data logging functions and return to
measurement mode.
4.8.3 Viewing/deleting stored record
This function provides the user with the ability to view/delete a record in a desired file
previously saved in memory. Following is the steps:
1. Press the key to activate the data logging functions. It will display the current file
name and the total record count of the file.
2. Use the key and the key to select the desired file.
3. Press the key to enter the selected file. It will display the current record number (for
example, L012) and the record content.
4. Use the key and the key to select the desired record.
5. Press the key on the desired record. It will automatically delete this record, and
display “-DEL”.
6. Press the key to exit the data logging functions and return to measurement mode.

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4.9 Data Printing
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. This
function is only available for AT300, and not for other models.
1. Before printing, please insert one connection plug of the print cable (Optional parts) into
the socket on the up-left of the main body, and insert the other plug into the
communication socket of the mini-printer.
2. Press the key to activate the data logging functions.
3. Use the key and the key to select the desired file.
4. Press the key to print the selected file. This operation will send all the data in
current file to the mini printer via RS232 port and print them out.
5. Press the key to exit the data logging functions and return to measurement mode.
4.10 Beep Mode
When the beep is set to 【On】，it would make a short hoot while press the key each
time, on each measurement, or the measured value exceeds the tolerance limit.
Press the key to switch the beep mode on and off. It will display the current beep
mode on the main screen.
4.11 EL Backlight
With the background light, it is convenient to work in the dark condition. Press key
to switch on or switch off the background light at any moment as you need after power on.
Since the EL light will consume much power, turn on it only when necessary.
4.12 Battery Information
Two AA size alkaline batteries are needed as the power source. After several hours’
usage of the preset batteries, the battery symbol on the screen will be shown as .
The more of dark part indicates the more close to fill. When the battery capacity runs out,
the battery symbol will be shown as and will begin to flash. When this occurs, the
batteries should be replaced.
Please take out the batteries when not working during a long period of time.
4.13 Auto Power Off
The instrument features an auto power off function designed to conserve battery life. If
the tool is idle for 5 minutes, it will turn itself off. While the voltage of the battery is too low
this function will also work.
4.14 System Reset
Press down the key while powering on the instrument will restore factory defaults.
All the memory data will be cleared during system reset. The only time this might possibly
helpful is if the parameter in the gauge was somehow corrupted.
4.15 Connecting to a Computer
AT300 is equipped with a RS232 serial port. Using the accessory cable, the gauge has
the ability to connect to a computer, or external storage device. Measurement data stored in
the memory of the gauge can be transferred to the computer through the RS232 port.
Detailed information of the communication software and its usage refer to the software

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manual.
5 Servicing
When the hardness tester appears some other abnormal phenomena, please do not
dismantle or adjust any fixedly assembled parts. Fill in and present the warranty card to us.
The warranty service can be carried on.
6 Transport and Storage
1) Keep it away from vibration, strong magnetic field, corrosive medium, dumpiness and
dust. Storage in ordinary temperature.
2) With original packing, transport is allowed on the third grade highway.
Appendix A Sound Velocities
Material
Sound Velocity
In/us
m/s
Aluminum
0.250
6340-6400
Steel, common
0.233
5920
Steel, stainless
0.226
5740
Brass
0.173
4399
Copper
0.186
4720
Iron
0.233
5930
Cast Iron
0.173-0.229
4400－5820
Lead
0.094
2400
Nylon
0.105
2680
Silver
0.142
3607
Gold
0.128
3251
Zinc
0.164
4170
Titanium
0.236
5990
Tin
0.117
2960
Epoxy resin
0.100
2540
Ice
0.157
3988
Nickel
0.222
5639
Plexiglass
0.106
2692
Polystyrene
0.092
2337
Porcelain
0.230
5842
PVC
0.094
2388
Quartz glass
0.222
5639
Rubber, vulcanized
0.091
2311
Teflon
0.056
1422
Water
0.058
1473

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Appendix B Applications Notes
Measuring pipe and tubing.
When measuring a piece of pipe to determine the thickness of the pipe wall, orientation
of the transducers is important. If the diameter of the pipe is larger than approximately 4
inches, measurements should be made with the transducer oriented so that the gap in the
wearface is perpendicular (at right angle) to the long axis of the pipe. For smaller pipe
diameters, two measurements should be performed, one with the wearface gap
perpendicular, another with the gap parallel to the long axis of the pipe. The smaller of the
two displayed values should then be taken as the thickness at that point.
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 100℃, 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 on a sample
piece of known thickness, which is at or near the temperature of the material to be
measured. This will allow the gauge 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 transducer. These transducers are built using
materials which can withstand high temperatures. Even so, it is recommended that the
probe be left in contact with the surface for as short 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

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impede accurate measurement of total material thickness, it does provide the user with
positive indication of air gaps in the laminate.
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.
Couplants
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 used in ultrasonic thickness measurement does not travel through air efficiently.
A wide variety of couplant materials may be used in ultrasonic gauging. Propylene
glycol is suitable for most applications. In difficult applications where maximum transfer of
sound energy is required, glycerin is recommended. However, on some metals glycerin can
promote corrosion by means of water absorption and thus may be undesirable. Other
suitable couplants for measurements at normal temperatures may include water, various oils
and greases, gels, and silicone fluids. Measurements at elevated temperatures will require
specially formulated high temperature couplants.
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 while in standard pulse-echo mode. This may result in a thickness reading that is
TWICE what it should be. The Responsibility for proper use of the instrument and
recognition of these types of phenomenon rests solely with the user of the instrument.
NOTE: Because of AKTEK’s policy of improving their products, the AT300 would
be revised and improved. Please inform us about misunderstandings or errors
which you may find in this manual comparing it to the device you bought. Do not
hesitate to contact us to suggest how to improve our devices. Thank You.
Aktek Endüstriyel Ekipman ve Enstrümantasyon Ltd.Şti.
Perpa Tic. Merkezi A-Blok Kat:11 No:1582
Okmeydanı-İstanbul-Türkiye
Phone: [phone] Fax: [phone]
www.aktek.com.tr [e-mail]