MITECH MT150 User manual

Ultrasonic Thickness Gauge
MT150/160
User’s Manual
MITECH CO., LTD.
www.mitech-ndt.com
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CONTENTS
1 Overview............................................................................................................................................................. 3
1.1 Product Specifications.............................................................................................................................3
1.2 Main Functions......................................................................................................................................... 4
1.3 Measuring Principle................................................................................................................................. 4
1.4 Configuration.............................................................................................................................................4
1.5 Operating Conditions...............................................................................................................................5
2 Structure Feature............................................................................................................................................. 5
2.1 Main Screen.............................................................................................................................................. 5
2.2 Keypad Definitions...................................................................................................................................6
3 Preparation........................................................................................................................................................ 6
3.1 Transducer Selection...............................................................................................................................6
3.2 Condition and Preparation of Surfaces................................................................................................ 8
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....................................................................................................................................... 11
4.8 Memory Management........................................................................................................................... 12
4.9 Data Printing........................................................................................................................................... 12
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.......................................................................................................................................................... 13
6 Transport and Storage..................................................................................................................................13
Appendix A Sound Velocities........................................................................................................................ 14
Appendix B Applications Notes.................................................................................................................... 14
User Notes...........................................................................................................................................................17
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1 Overview
The model MT150/MT160 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
Display：4.5 digits LCD with EL backlight.
Measuring Range：(0.75～300)mm (in Steel).
Sound Velocity Range: (1000~9999) m/s.
Resolution：MT150: 0.1mm; MT160: 0.1mm/0.01mm
Accuracy：±（0.5%Thickness+0.04）mm, depends on materials and conditions
Units: Metric/Imperial unit selectable.
Four measurements readings per second for single point measurement, and ten per second for
Scan Mode.
Memory for up to 20 files (up to 99 values for each file) of stored values.
Power Source：Two “AA” size, 1.5 Volt alkaline batteries. 100 hours typical operating time (EL
backlight off).
Communication：RS232 serial port for MT160. No communication port for MT150.
Outline dimensions：150mm×74mm×32 mm.
Weight：245g
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1.2 Main Functions
Capable of performing measurements on a wide range of material, including metals, plastic,
ceramics, composites, epoxies, glass and other ultrasonic wave well-conductive materials.
Transducer models are available for special application, including for coarse grain material and
high temperature applications.
Probe-Zero function, Sound-Velocity-Calibration function
Two-Point Calibration function.
Two work modes: Single point mode and Scan mode.
Coupling status indicator showing the coupling status.
Battery information indicates the rest capacity of the battery.
Auto sleep and auto power off function to conserve battery life.
Optional software to process the memory data on the PC for MT160.
Optional thermal mini-printer to print the measured data via RS232 port for MT160.
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. 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
MT160.
13
Print cable
1
14
DataPro Software
1
15
Communication
Cable
1
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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
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
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.
Unit: Current unit system. MM or IN for thickness value. M/S or IN/μS for sound velocity.
Battery Information: Display the rest capacity of the battery.
Information Display: Displays the measured thickness value, the sound velocity and shows
hints of current operation.
POWER: 2 X 1.5V
SN:
ULTRASONIC
THICKNESS GAUGE
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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 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
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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 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)
20mm
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）
30mm
For high temperature
(lower than 300℃)
measurement.
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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 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. 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.
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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.
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.
1Perform a Probe-Zero.
2Apply couplant to the sample piece.
3Press 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.
4Having achieved a stable reading, remove the transducer. If the displayed thickness changes
from the value shown while the transducer was coupled, repeat step 3.
5Press the key to activate the calibration mode. The MM (or IN) symbol should begin
flashing.
6Use the key and the key to adjust the displayed thickness up or down, until it
matches the thickness of the sample piece.
7Press 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.
8Press 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.
1Press the key to activate the calibration mode. The MM (or IN) symbol should begin
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flashing.
2Press the key again, so that The M/S (or IN/μS) symbols are flashing.
3Use 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.
4Press the key to exit from the calibration mode. The gauge is now ready to perform
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.
1Perform a Probe-Zero.
2Apply couplant to the sample piece.
3Press 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.
4Having achieved a stable reading, remove the transducer. If the displayed thickness changes
from the value shown while the transducer was coupled, repeat step 3.
5Press the key. The MM (or IN) symbol should begin flashing.
6Use the key and the key to adjust the displayed thickness up or down, until it
matches the thickness of the sample piece.
7Press the key. The display will flash 1OF2. Repeat steps 3 through 6 on the second
calibration point.
8Press 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.
9Press 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
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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 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
MT160 has selectable display resolution, which is 0.1mm and 0.01mm. This function is not
available for MT150, which is fixed to 0.1mm.
Press down the key while turning on the gauge will switch the resolution between “High” and
“Low”.
4.7 Changing Units
On the measurement mode, press the key to switch back and forth between imperial and
metric units.
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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:
1Press the key to activate the data logging functions. It will display the current file name
and the total record count of the file.
2Use the key and the key to select the desired file to set as current file.
3Press 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.
1Press the key to activate the data logging fuctions. It will display the current file name and
the total record count of the file.
2Use the key and the key to scroll to the file that will be cleared of all measurements.
3Press the key on the desired file. It will automatically clear the file, and display “-DEL”.
4Press 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:
1Press the key to activate the data logging functions. It will display the current file name
and the total record count of the file.
2Use the key and the key to select the desired file.
3Press the key to enter the selected file. It will display the current record number (for
example, L012) and the record content.
4Use the key and the key to select the desired record.
5Press the key on the desired record. It will automatically delete this record, and display
“-DEL”.
6Press the key to exit the data logging functions and return to measurement mode.
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
MT160, and not for MT150.
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.
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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
MT160 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 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
Keep it away from vibration, strong magnetic field, corrosive medium, dumpiness and dust.
Storage in ordinary temperature.
With original packing, transport is allowed on the third grade highway.
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Appendix A Sound Velocities
Material
Sound Velocity
in/µs
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
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
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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 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.
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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.
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User Notes
Warranty：
The product is guaranteed for one year since purchased. Log www.mitech-ndt.com or follow our
company official public platform to register for maintenance. Please fill the blanks as required, if the
product is not registered for maintenance, it will follow the date of manufacturer.
When applying for maintenance, please visit our official website, www.mitech-ndt.com or official
accounts, submit “online reporting to repair” sheet.
In accordance with the international relevant regulations, the following are not within the scope of free
warranty,
Damage caused by man-made or improper keeping;
Self-dismantle or non-special repair shop dismantle;
Do not follow the requirement of service registration or warranty expired;
Consumable parts.
Service promise：
MITECH users have lifelong maintenance service
Free maintenance, inspection, software upgrade and etc.
Add ：Room E506B, YingChuangDongLi Park, 1# of ShangDi East Road, Haidian District, Beijing,
China
Post code：100094
Website：www.mitech-ndt.com
Email：[e-mail]
Tel：[phone]
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