OKOndt GROUP UTG-8 User manual

ULTRASONIC THICKNESS GAUGE
UTG-8
Quick start guide
www.oko-ndt.com

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CONTENTS
P.
1 PURPOSE.................................................................................................................................................2
2 MAIN SPECIFICATIONS ....................................................................................................................3
3 COMPOSITION AND OPERATION.................................................................................................6
4 SETTING-UP PROCEDURE............................................................................................................ 14
5 OPERATION PROCEDURE............................................................................................................. 22
6 INFORMATION ABOUT MANUFACTURER ............................................................................ 24

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1PURPOSE
1.1 UTG-8 ultrasonic thickness gauge is intended for:
―measuring the thickness of various materials with only one-side access to
them;
―measuring the propagation velocity of ultrasonic waves in different metals
with a known thickness.
1.2 The thickness gauge can be applied in various industries for measuring the
wall thickness of vessels, pipes, body parts, sheets, etc., including the ones with
corroded surfaces, during production and operation.
1.3 The thickness gauge is serviced by one operator.
It is allowed to use the thickness gauge only after the present operation manual
has been carefully read.

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2MAIN SPECIFICATIONS
2.1 Main parameters and dimensions
2.1.1 The thickness gauge consists of an electronic unit and piezoelectric
transducer.
2.1.2 The range of thickness measurements (for steel) varies from 0.6 to
500 mm.
2.1.3 The range of thickness measurements (for steel) by different transducers
corresponds to the values indicated in Table 1.
Table 1 –Transducer designations and measurement ranges
Transducer designation
Measurement range (for steel), mm
.250” 5 MHz
.500” 5 MHz
.187” 7.5 MHz
.250” 7.5 MHz
.187” 10 MHz
1.2 ÷ 150 mm
1.2 ÷ 500 mm
1.0 ÷ 50 mm
0.6 ÷ 150 mm
1.0 ÷ 50 mm
2.1.4 The measurement range of ultrasonic waves propagation velocity varies
from 1250 to 10000 m/s.
2.1.5 Value of the smallest indication digit is as follows:
―for measuring the ultrasound propagation velocity –1.0 m/s;
―for measuring the product thickness of less than 199.99 mm –0.01 mm;
―for measuring the product thickness of more than 200.00 mm –0.1 mm.
2.1.6 Time of the thickness gauge operation mode setup is up to 10 s.
2.1.7 Power supply of the thickness gauge is provided by three alkaline “ААА”
batteries (1.5 V) or nickel-cadmium cells (1.2 V).
2.1.8 Time of continuous thickness gauge operation on alkaline batteries and
with backlighting switched off is about 200 hours, on nickel-cadmium cells –about
120 hours.
2.1.9 Overall dimensions of electronic unit of the thickness gauge are no more
than 35 mm × 70 mm × 125 mm.

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2.1.10 The thickness gauge weight with one piezoelectric transducer (without
spare parts, accessories and bag) is no more than 0.176 kg.
2.2 Specifications
2.2.1 The limits of allowable basic absolute error for thickness measurement
are ± (0.03 + 0.002·Hx) mm, where Hx is a numeric thickness value expressed in
millimeters.
2.2.2 The limits of allowable relative error for ultrasound propagation velocity
measurement are ± 1.5 % of the measured value.
2.2.3 The limits of allowable complementary error of the thickness gauge for
thickness measurement, which occurs due to the variation of ambient temperature
by every 10 °Сfrom the temperature range limits (20 ± 5) °Сin the operating
temperature interval are ± 0.5·ΔН, where ΔН is a value of absolute thickness
measurement error expressed in mm.
2.2.4 The limits of allowable complementary error of the thickness gauge for
thickness measurement from a rough surface side, which occurs due to the surface
roughness Rz= 40 µm, are no more than ± 0.5·ΔН.
2.2.5 The limits of allowable complementary error of the thickness gauge,
occurred due to the surface roughness Rz = 160 µm for .187” 7.5 MHz, .500” 5 MHz,
.187” 10 MHz transducers, and Rz = 80 µm for .250” 5 MHz, .250” 7.5 MHz transducers
during the thickness measurement from a smooth surface side, are no more than
± 0.5·ΔН.
2.2.6 The limits of allowable complementary error of the thickness gauge for
measuring the thickness of curved surfaces with the curvature radius of 10 mm for
.187” 7.5 MHz, .250” 7.5 MHz transducers, and curvature radius of 20 mm for
.250” 5 MHz, .187” 10 MHz transducers, are ± 0,5·ΔН.
2.2.7 The limits of allowable complementary error of the thickness gauge for
measuring the thickness of nonparallel surfaces with the out-of-parallelism of 3 mm
on the reference length of 20 mm, are ± 0,5·ΔН, mm, in the range from 1 to 10 mm,
and ± (0.2 + 0.01Hx) mm, where Hx is a numeric thickness value expressed in
millimeters, in the range from 10 to 50 mm.
2.2.8 When operated, the thickness gauge is resistant to the effect of the
following climatic factors:
―ambient air temperature from - 20 to + 50 °С;
―relative air humidity up to 95 % at 35 °С, without condensation;
―atmospheric pressure from 84 to 106.7 kPa.
2.2.9 The degree of thickness gauge case protection against the ingress of
solids and water corresponds to IР64.

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2.2.10 The thickness gauge in its transportation packing is resistant to the effect
of the following climatic factors:
―ambient air temperature from - 40 to + 55 °С;
―relative air humidity up to 98 % at 35 °С.
2.2.11 The mean expected time to first failure of the thickness gauge is no less
than 32000 hours.
Failure criterion is non-conformity to para 2.1.3, 2.2.1.
2.2.12 The mean total lifetime of the thickness gauge without transducers till its
limit state, taking into account the spare parts and maintenance in accordance with
the regulatory documents, is no less than five (5) years.
The limit state criterion for the thickness gauge is economic inexpedience of its
repair in order to restore the instrument performance.
2.2.13 The mean total lifetime of transducers is no less than six (6) months*.
* if testing is carried out on surfaces, whose roughness does not exceed Rz 80,
and maintenance is performed according to para 8.1.

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3COMPOSITION AND OPERATION
3.1 Outer appearance of the thickness gauge is illustrated on Fig. 1.
Fig. 1–Outer appearance of UTG-8 thickness gauge
3.2 Functions of keys:
« » - this key is used to turn the thickness gauge ON and OFF.
When the gauge is turned ON, it will first perform a brief display test by
illuminating all of the segments in the display. After one second, the gauge will
display the internal software version number. After that, the display will show
"0.000" (or "0.00" if metric units were used for measurements before the last
switch-off of the instrument), indicating the gauge is ready for use.
The thickness gauge is turned OFF by pressing the ON/OFF key. All settings are
saved after the gauge has been turned off.
The gauge also features an auto-powerdown mode designed to conserve the
battery life. If the gauge is idle for 5 minutes, it will automatically turn itself off.
« » - this key is used to “zero” the thickness gauge (delay calibration in the
wedge of piezoelectric transducer together with hardware delays).

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The correctness of the above operation affects the measurement accuracy.
“Zero” calibration procedure is detailed in para. 6.6 of this Manual.
« » - the CAL key serves to enter and exit the calibration mode. This mode
is used to adjust the ultrasound velocity value that will be applied for thickness
calculation. Calibration can be performed based on a known thickness, known
ultrasound velocity, or on two points.
The procedure of thickness gauge calibration with a known ultrasound velocity
is detailed in para 6.7 of this Manual.
The procedure of thickness gauge calibration with an unknown ultrasound
velocity is detailed in para 6.8 of this Manual.
The procedure of thickness gauge two-point calibration is detailed in para 6.9
of this Manual.
« » - the IN/MM key is used to switch back and forth between metric and
inch units. This key may be used at any time, whether the gauge is displaying a
thickness (in or mm) or ultrasound velocity value (in/µs or m/s).
« » - the UP arrow key has two functions. When the thickness gauge is in
calibration mode, this key is used to increase numeric values on the display. In
normal mode, this key takes the gauge into scanning mode.
Detailed description of the scanning mode can be found in para 7.7 of this
Manual.
« » - the DOWN arrow key has two functions. When the thickness gauge is
in calibration mode, this key is used to decrease numeric values on the display. In
normal mode, it serves for setting up one of the three display backlight modes –
“Off” / “Auto” / “On”.
“Off” will be displayed when the backlight is switched off.
In the “Auto” mode, the backlight will illuminate when the gauge is actually
making a measurement.
“On” will be displayed when the backlight is set to stay on.

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3.3 Display
To show information on the display, the thickness gauge uses 4 main digits and
some additional indicators, the functions of which are described below.
Fig. 2–Outer appearance of display
When the gauge is displaying thickness measurements, the display will hold the
last value measured, until a new measurement is made.
Besides, when the battery charge is low, “” icon starts flashing in the upper
left corner of the display. If this happens, it is necessary to replace (or recharge)
the battery.
This indicator shows the stability of thickness measurement (16
vertical bars). If the measurement is stable, more than a half of
such vertical bars should be displayed.
When the “in” symbol is on, all thickness measurements are
made in inches. The maximum thickness that can be displayed is
19.999 inches.
When the “mm” symbol is on, all thickness measurements are
made in millimeters. The maximum thickness (for steel) that
can be displayed is 600 mm.
When the “in/us” symbol is on, the velocity of ultrasonic waves
is measured in inches-per-microsecond.

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When the “m/s” symbol is on, the velocity of ultrasonic waves is
measured in meters-per-second.
Numeric (main) field of the display consists of five digits. This
field is used to show numerical values, as well as simple words in
different operation modes of the thickness gauge.
When performing the manual thickness measurement, “M”
indicator is illuminated on the display.
When switching on the scanning mode, “S” indicator is
illuminated on the display.
“H1”indicator appears after pressing button, which serves
for calibration of ultrasound velocity at a known thickness (1
point calibration). For details, please refer to para 6.8 of this
Manual.
“H2”indicator appears during the 2 point calibration. For details,
please refer to para 6.9 of this Manual.
“Z” indicator appears during zero calibration (wedge).

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“V” indicator appears during the calibration at a known
ultrasound velocity in a test object. For details, please refer to
para 6.7 of this Manual.
“Prb0” symbol is on, after the zero calibration has been finished.
For details, please refer to para 6.6 of this Manual.
“Auto” symbol indicates that automatic display backlight mode is
switched ON. For details, please refer to para 6.5 of this Manual.
“On” symbol indicates that permanent display backlight mode is
switched ON. For details, please refer to para 6.5 of this Manual.
“Off” symbol indicates that display backlight mode is switched
OFF. For details, please refer to para 6.5 of this Manual.
“1-OK” symbol indicates the two point calibration, namely
calibration of the 1st point. For details, please refer to para 6.9 of
this Manual.
“2-OK” symbol indicates the two point calibration, namely
calibration of the 2nd point. For details, please refer to para 6.9 of
this Manual.
Battery charge indicator.

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3.4 Operation principle of the thickness gauge is based on ultrasonic pulse-
echo method of measurement, which utilizes the property of ultrasonic waves to
reflect from interface of media with different acoustic impedances.
Piezoelectric plate of dual element transducer generates an ultrasonic pulse
through a delay line (wedge) in the direction of outer surface of a product, whose
thickness is to be measured. The ultrasonic pulse propagates in the product up to the
opposite surface, reflects from it, goes in reverse direction, and having passed the
delay line (wedge), it is accepted by receiving piezoelectric plate. Time of ultrasound
propagation from one surface of a product to another and back depends on the
product thickness:
, (1)
where Н–thickness of test product;
С–velocity of ultrasound propagation in the product’s material;
t –time of ultrasound propagation from one surface to another and back.
3.5 Schematic structure of the thickness gauge is shown on Fig.3.
3.6 The thickness gauge consists of a piezoelectric transducer and electronic
unit.
3.6.1 Piezoelectric transducer
Transducer types, ranges of thickness values to be measured, and dimensions of
work surfaces are listed in Table 1.
3.6.2 The electronic unit induces a high-voltage sounding pulse in order to
excite the transducer, amplify the signal exiting the transducer, generate and
measure a time interval, which corresponds to the time of ultrasound propagation
from one edge of a test product to another, as well as mathematical processing of
obtained data, storage of variable and intermediate measurement results, control of
operation modes, and display of measurement results in thickness units.

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PET –piezoelectric transducer;
SPG –sound pulse generator;
K –keypad;
LCD –liquid crystal display;
A –amplifier;
TIM –time interval meter;
PS –power supply.
Fig. 3- Schematic structure of UTG-8 thickness gauge
3.7 The thickness gauge can be operated in the following modes:
−“Measurement” –basic operation mode of the gauge. The product thickness is
measured in this mode;
−“0 calibration” –this mode is designed to compensate the time of ultrasound
propagation in the transducer wedge during thickness measurement;
−“V calibration” –this mode is intended for setting up the velocity (V) of
ultrasound propagation in the material of test product;
−“T calibration” –this mode is used to determine the velocity of ultrasound
propagation in the material of test product at a known thickness (T);
−“Two point calibration” –this mode is designed to compensate the time of
ultrasound propagation in the transducer wedge (estimating the delay in the
transducer wedge) and to determine the velocity of ultrasound propagation in the
material of test product by two thickness calibration gages.
LCD
TIM
A
SPG
PET
K
Electronic unit
Microprocessor
PS

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3.8 Design
Electronic circuit of the thickness gauge is assembled on a PCB, housed in a
plastic case. Power supply source comprised by three (3) ‘ААА’ battery cells is placed
inside the case.
The bottom panel of the case includes a 5-mm thick probe disc (Fig. 4). The top
panel of the case includes connectors for transducers (Fig. 5).
Fig. 4 –Bottom panel of the thickness gauge
Fig. 5 –Top panel of the thickness gauge

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4SETTING-UP PROCEDURE
4.1 Test object surface preparation
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, thickness measurements. The surface being measured should be clean
and free of any small particles, 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, sanders or
grinding machines may be used, after which the test surface should be cleaned of
resulting abrasive dust and chips.
Extremely rough surfaces, such as castings, will prove most difficult to measure
due to diffusion of ultrasonic waves.
Besides, rough surfaces contribute to excessive wear of the transducer,
particularly in situations where the transducer is "scrubbed" along the test surface.
Therefore, the transducers should be checked for wear on a regular basis.
4.2 Transducer selection
The thickness gauge is inherently capable of performing measurements on a
wide range of various materials. 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 important properties of transducers 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, so that a strong, stable echo-
signal is received by the thickness gauge.
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.
Furthermore, as ultrasound travels through any material, it is partly absorbed or
scattered. The higher grain coarseness of the material, the more ultrasonic energy is
scattered.
The higher the frequency of ultrasonic waves, the more ultrasonic energy is
absorbed and scattered. While it may seem that using a lower frequency transducer
might be better in every instance, a higher frequency transducer would be the best
choice for testing objects with small thicknesses.
The physical constraints of measuring environment may also determine a
transducer's suitability for a given job. Some transducers may simply be too large to

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be used in tightly confined areas. Besides, the choice of a transducer can also be
affected by the curvature of tested surface, since the establishment of ultrasonic
contact between a transducer and tested surface is of paramount importance while
making the measurements.
The choice of a proper transducer often becomes an issue of finding a
compromise between different characteristics. A need may arise to try different
transducers in order to find the one which would best suit a specific job.
4.3 Transducer connection
Choose a proper transducer for the required thickness range of products to be
tested. Plug the connecting cable “Transducer/Thickness gauge” in the connector on
the thickness gauge (Fig. 5).
The connecting cable “Transducer/Thickness gauge” is structurally included
into the transducer set.
4.4 Switching the thickness gauge ON
Switch the thickness gauge ON (by pressing button) and make sure that
the battery is not exhausted (“ ” icon should not be flashing).
In case the batteries (or cells) are discharged, replace them with new ones (see
para 8.2) or charge the batteries using an external charging device (not included into
the thickness gauge delivery set).
When the battery charge is low, “” icon will start flashing in the upper left
corner of the display:
Fig. 6
Note - When switched on, the thickness gauge is automatically placed in the
“Measurement” mode, saving all the settings, which were active before its prior
turning off.

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4.5 Selection of display backlight mode
By successive pressing of button, select the desired display backlight
mode:
-“Auto” –the backlight will illuminate when the gauge is actually making a
measurement;
-“On” –this mode will be displayed when the backlight is set to stay on;
-“Off” –this mode will be displayed when the backlight is switched off.
Note - It should be borne in mind that the selected display backlight mode
affects the continuous operation time of the thickness gauge.
4.6 Zero calibration
ATTENTION!
Zero calibration (time compensation of ultrasound propagation in the
transducer wedge) is important for correct thickness measurement. If the gauge is
not "zeroed" correctly, all measurements the gauge makes will be erroneous by some
fixed percentage. When the UTG-8 is "zeroed", this fixed error value is measured and
automatically corrected for in all subsequent measurements.
For zero calibration, please perform the following actions:
1) Plug an appropriate transducer into the thickness gauge using the
connecting cable.
2) Switch the thickness gauge ON by pressing button.
3) Apply a few droplets of couplant onto the built-in 5mm thick probe disc
(Fig. 4).
4) Press the transducer against the probe disc, making sure that the
transducer sits flat against the probe disc surface. The display should show some
thickness value, and the Stability Indicator should have nearly all its bars illuminated.
Fig. 7

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Note - Zero calibration of the thickness gauge should be performed only on the
built-in 5mm thick probe disc.
5) Remove the transducer from the probe disc and press button.
After that, the display will show a message (Fig. 8) about the successful zero
calibration, along with a shortly-displayed measured value of ultrasound propagation
delay in the transducer wedge (in µs), which will be used for subsequent
measurements.
Fig. 8
Notes:
1 Calibration can be also done with a transducer placed on the surface of a
calibration block.
2 After the calibration is completed, “zero” value (time delay) will be saved to
the memory of the thickness gauge, and will be used for further measurements.
ATTENTION!
Before starting the operation, always perform the wedge delay calibration.
4.7 Thickness gauge calibration at a known ultrasound velocity (“V
calibration”)
Note - This procedure requires that the operator know the ultrasound velocity
of the material to be tested.
For the thickness gauge calibration at a known ultrasound velocity, please
perform the following actions:
1) Plug an appropriate transducer into the thickness gauge using the
connecting cable.
2) Switch the thickness gauge ON by pressing button.
3) Carry out zero calibration in accordance with para 6.6. Press twice
button. The “m/s” or “in/us” symbols will start flashing on the display, with “V”

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symbol illuminated, and the main indicator will show the ultrasound velocity value
(Fig. 9).
Fig. 9
4) Using and keys, adjust the displayed velocity up or down, until it
matches the actual (true) ultrasound velocity of the material to be measured.
5) Press key once again to exit the calibration mode.
6) The thickness gauge is now ready to perform measurements.
Note - After the calibration is completed, the ultrasound velocity value will be
saved to the memory of the thickness gauge, and will be used for further
measurements.
4.8 Thickness gauge calibration at an unknown ultrasound velocity (“One point
calibration”)
Note - For the thickness gauge to perform accurate measurements, the velocity
of ultrasonic waves in the material of a test object should be set up correctly.
Since the material composition (and thus, its ultrasound velocity) may vary from
lot to lot and from manufacturer to manufacturer, the calibration to a sample of
known thickness made of the same material as a test object will ensure the most
accurate measurements.
For the calibration to a known thickness, please perform the following actions:
1) Plug an appropriate transducer into the thickness gauge using the
connecting cable.
2) Switch the thickness gauge ON by pressing button.
3) Carry out zero calibration in accordance with para 6.6.
4) Press the transducer against the sample of a known thickness prior wetted
with couplant, 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 more than a half of its vertical bars on.

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5) Press key, after which the main indicator will show the thickness value,
the “H1” symbol will appear on the display, and the “mm” symbol will start flashing.
6) Remove the transducer from the sample piece.
7) Using and keys, adjust the displayed thickness up or down, until
it matches the actual (true) thickness of the sample piece.
8) Press key, after which the calculated ultrasound velocity of the
calibration sample will be displayed in the main indicator field, the “V” symbol will
appear, and in a short period of time the “V” symbol will change to “M” symbol, the
“m/s” symbol will change to “mm” symbol, and the main indicator field will show the
resulting measured thickness (Fig. 10).
Fig. 10
The thickness gauge is now ready to perform measurements.
Note - After the calibration is completed, the ultrasound velocity value will be
saved to the memory of the thickness gauge, and will be used for further
measurements.
4.9 Two point calibration of the thickness gauge
Note - Two sample pieces of a known thickness are required to perform the two-
point calibration of the thickness gauge.
For the two-point calibration, please perform the following actions:
1) Plug an appropriate transducer into the thickness gauge using the
connecting cable.
2) Switch the thickness gauge ON by pressing button.
3) Press the transducer against the 1st sample of a known thickness prior
wetted with couplant, making sure that the transducer sits flat against the surface of
the 1st sample. The Stability Indicator should have nearly all vertical bars on.