Elcometer SG80 User manual

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Model SG80
Sonic Gauge
Operating Instructions

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This product meets the Electromagnetic Compatibility Directive.
These operating instructions are available for download on our website www.elcometerndt.com.
The following trademark is a registered trademark of Elcometer Limited, Edge Lane, Manchester, M43 6BU. United
Kingdom:
All other trademarks acknowledged.
© Elcometer Limited 2011. All rights reserved. No part of this document may be reproduced, transmitted, transcribed,
stored (in a retrieval system or otherwise) or translated into any language, in any form or by any means (electronic,
mechanical, magnetic, optical, manual or otherwise) without the prior written permission of Elcometer Limited.
TMA-0507 Issue 01
Text with cover : 23164

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Contents
1 About your Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 The Keypad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 The Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Setting up the Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6 Measurement - Taking Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7 Scan mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10 Technical Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
12 Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
13 Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
14 Condition and Preparation of Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
15 Application Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
16 Sound Velocities of Common Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

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Thank you for purchasing this Elcometer NDT product. Welcome to Elcometer NDT.
The Model SG80 Velocity Gauge is a world beating product. With the purchase of this gauge you now have
access to the worldwide service and support network of Elcometer NDT. For more information visit our
website at www.elcometerndt.com.
1 ABOUT YOUR GAUGE
The Model SG80 is a sonic gauge that measures with extreme versatility. It has the ability to measure the
thickness of a material while maintaining the ability to locate pits, flaws and defects in the material. Based
on the same operating principles as SONAR, the Model SG80 is capable of measuring the thickness of
various materials with accuracy as high as 0.01 millimetres (0.001 inches). The principal advantage of
ultrasonic measurement over traditional methods is that ultrasonic measurements can be performed with
access to only one side of the material being measured.
1.1 STANDARDS
Your gauge can be used in accordance with the following Standards and test methods; ASTM E 797,
EN 14127 and EN 15317.
1.2 WHAT THIS BOX CONTAINS
Model SG80, Bottle of couplant, Battery (2 x), Carrying case, Test certificate, Operating instructions.
Note: The box does not include a transducer; these must be ordered separately. To order a transducer,
contact Elcometer NDT or your local Elcometer NDT supplier.

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1.3 PACKAGING
The gauge is packed inside its carry case within a cardboard box. Please ensure that the packaging is
disposed of in an environmentally sensitive manner. Consult your Local Environmental Authority for further
guidance.
To maximise the benefits of your new Elcometer NDT gauge, please take some time to read these
Operating Instructions. Do not hesitate to contact Elcometer NDT or your Elcometer NDT supplier if you
have any questions.

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2 THE KEYPAD
Key Functions
Press to switch the gauge on or off.
When switching off, the gauge retains all of its settings.
If the gauge is idle for 5 minutes, it will switch itself off.
Press to change units (metric/imperial)
This key has two functions:
• Gauge in calibration mode: Increases numeric values on the display (press and hold to
increase quickly).
• Gauge not in calibration mode: Switches the Scan measurement mode on and off.
This key has two functions:
• Gauge in calibration mode: Decreases numeric values on the display (press and hold to
decrease quickly).
• Gauge not in calibration mode: Switches the display backlight between three settings;
on, off and auto (in auto mode the backlight automatically illuminates while the gauge is
making a measurement and switches off after several seconds, conserving battery life).
Press to zero the gauge.
Press to calibrate the gauge.
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3 GETTING STARTED
3.1 FITTING BATTERIES
Your gauge may be used with dry cell batteries or rechargeable
batteries. 2 x LR6 (AA) alkaline batteries are supplied with this gauge.
When the battery voltage is low the entire display will start to flash. When
this occurs the batteries should be replaced.
To fit or replace batteries:
1. Locate battery compartment cover at top of gauge.
2. Unscrew battery compartment cover.
3. Referring to battery polarity instructions on rear of gauge, insert bat-
teries into gauge ensuring correct polarity.
4. Replace battery compartment cover.
Note: Remove the batteries from the gauge if it is to remain unused for
a long period of time. This will prevent damage to the gauge in the event
of malfunction of the batteries.
3.2 CHOOSING THE TRANSDUCER
When you purchased your gauge you should have also purchased a
suitable transducer for your application. If you have not yet done so, refer
to “Transducers” on page 22, which will help you identify the correct
transducer type. Alternatively contact Elcometer NDT, your local
Elcometer NDT supplier or visit www.elcometerndt.com
Battery
compartment
cover
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3.3 FITTING THE TRANSDUCER
The transducer transmits and receives ultrasonic sound
waves that the gauge uses to calculate the speed of sound in
the material being measured.
The transducer connects to the gauge via the attached cable,
and two coaxial connectors. When using transducers
manufactured by Elcometer NDT, the orientation of the dual
coaxial connectors is not critical; either plug may be fitted to
either socket.
The transducer must be used correctly in order for the gauge to produce accurate, reliable measurements.
The illustration shows the two semicircles of the wearface and
the barrier separating them on a typical transducer.
One of the semicircles transmits ultrasonic sound into the
material being measured, and the other semicircle receives
the sound echoes back into the transducer. When the
transducer is placed against the material being measured, it is
the area directly beneath the centre of the wearface that is
being measured.
3.4 SWITCHING ON/OFF
To switch on or off, press the on/off key .
The gauge will switch off automatically after 5 minutes of inactivity.
Wearface

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4 THE DISPLAY
Note: The display will hold the last value measured, until a new measurement is made.
Note: When the battery voltage is low, the entire display will begin to flash. When this occurs, the batteries
should be replaced.
Stability indicator
• One vertical bar - no
readings are being taken
• Less than 5 bars - read-
ing is unstable and may
be inaccurate
• More than 5 bars - read-
ing is stable
Units (IN, MM, IN/µs, M/s)
Measurement value/Text
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5 SETTING UP THE GAUGE
5.1 TRANSDUCER - ZEROING
Setting the zero point for the transducer is important for the same reason that setting the zero on a
mechanical micrometer is important. If the zero point of the transducer is not set correctly, all of the
measurements the gauge makes will be in error by some fixed number. When the zero point of the
transducer is set, this fixed error value is measured and automatically corrected for in all subsequent
measurements.
Though the gauge will remember the last zero point, it is generally a good idea to set the zero point
whenever the gauge is switched on, as well as any time a different transducer is used. This will ensure that
the zero point of the instrument is always correct.
The zero probe routine must be done prior to calibration.
1. Switch on the gauge and connect the transducer.
2. Remove all couplant from the face of the transducer and check that the
wearface of the transducer is clean and free of any debris.
3. Apply a drop of couplant on the transducer and place the transducer in
steady contact with the probe zero disk (the battery cover located on
the top of the unit), and obtain a steady reading.
The display should show a thickness value, and nearly all the bars of
the stability indicator should be illuminated.
Note: The value that is displayed will change depending on the current
velocity setting in your gauge. Disregard the value displayed; it is not
important. What is important is accurately performing these steps to
ensure reliability of the zero calculation.
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4. While the transducer is firmly coupled to the disc, press .
The display will show ‘Prb0’ while it is calculating its zero point. When the probe zero is completed the
measurement screen is displayed.
5. Remove the transducer from the probe zero disk.
Your gauge should now be calibrated.
5.2 CALIBRATING
In order for the gauge to make accurate measurements, it must be calibrated to the sound-velocity of the
material being measured.
Different types of material have different sound-velocities. For example, the velocity of sound through steel
is 5918 m/s (about 0.233 in/µs) and the velocity of sound through aluminium is 6350 m/s (about
0.248 in/µs). 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.
There are two methods of calibrating your gauge:
Known thickness calibration: The gauge is calibrated by setting it to a single known thickness (one-point)
or two known thicknesses (two-point):
• One-point calibration is the simplest and most commonly used calibration procedure - optimising line-
arity over large ranges.
• Two-point calibration allows for greater accuracy over small ranges.
Known velocity calibration: The sound-velocity of the material being measured is entered directly into the
gauge.
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To achieve the most accurate measurements possible, it is generally advisable to calibrate the gauge to a
sample piece of known thickness. Material composition(andthus,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.
5.2.1 Known Thickness Calibration
If the sound velocity of a material is unknown, a sample of known thicknesses can be used to determine the
sound velocity.
Note: Known thickness calibration 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.
One-point Thickness Calibration: You should always calibrate on the high side of the intended range of
material thicknesses you will be measuring. For example, if you are measuring material ranging from
2.54 mm to 25.4 mm (.100" to 1.0"), you should calibrate on a known thickness sample close to 25.4 mm
(1.0").
Note: Before you start this calibration procedure, perform a probe zero.
1. Physically measure an exact sample of the material or a location directly on the material to be meas-
ured using a set of calipers or a digital micrometer.
2. Apply a drop of couplant on the transducer and place the transducer in steady contact with the sample
or the material being tested. Be sure that the reading is stable and the repeatability indicator, in the top
left corner of the display, is fully lit and stable.
3. Having achieved a stable reading, remove the transducer. If the displayed value changes from the
value shown while the transducer was coupled, repeat the previous step.

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4. Press .
On the display, MM (or IN) starts flashing on and off.
5. Use the and arrows to adjust the displayed thickness until it matches the thickness of the
sample of material.
6. Press again.
On the display, M/s (or IN/µs) starts flashing on and off.
The gauge now displays the sound velocity value it has calculated based on the thickness of the sam-
ple piece.
7. Press to exit the calibration routine.
Your gauge is now ready to perform measurements.
Two-point Thickness Calibration: For improved accuracy over a smaller measurement range, conduct a
two-point calibration. For example, if the measurement range is 2.03 mm to 6.35 mm (.080" to 0.250"),
perform the first calibration on a known thickness sample close to 6.35 mm (.250"), followed by the second
calibration close to 2.03 mm (.080").
Note: Before you start this calibration procedure, perform a probe zero.
1. Physically measure an exact sample of the material or a location directly on the material to be meas-
ured using a set of calipers or a digital micrometer. Measure two samples/locations.
2. Apply a drop of couplant on the transducer and place the transducer in steady contact with the first
sample/location of the material being tested. Be sure that the reading is stable and the repeatability
indicator, in the top left corner of the display, is fully lit and stable.
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3. Having achieved a stable reading, remove the transducer. If the displayed value changes from the
value shown while the transducer was coupled, repeat the previous step.
4. Press .
On the display, MM (or IN) will start flashing on and off.
5. Use the and arrows to adjust the displayed thickness until it matches the thickness of the
sample of material.
6. Press .
The display flashes 1OF2.
7. Repeat steps 2 to 6, this time with the transducer in contact with the second sample/location of the
material being tested.
The gauge displays the sound velocity value it has calculated based on the thicknesses of the sample
piece.
Your gauge is now ready to perform measurements.
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5.2.2 Known Velocity Calibration
If the material velocity is known, you can enter the velocity value directly into the gauge. A list of the sound
velocities of common materials is given at the end of this instruction manual.
Note: Before you start this calibration procedure, perform a probe zero.
1. Apply a drop of couplant on the transducer and place the transducer in steady contact with the sample
or the material being tested. Be sure that the reading is stable and the repeatability indicator, in the top
left corner of the display, is fully lit and stable.
2. Press .
On the display, M/s (or IN/µs) will start flashing on and off.
3. Use the and arrows to adjust the displayed sound-velocity until it matches the known
sound-velocity of the sample of material.
4. Press .
The display will show the thickness value calculated for the material.
5. Press to exit the calibration routine.
Your gauge is now ready to perform measurements.
Note: During the calibration procedure when M/s (or IN/µs) is flashing, if you press , the factory default
sound-velocity for steel will be restored (5920 m/s or 0.2330 in/µs).
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6 MEASUREMENT - TAKING READINGS
Disclaimer: Inherent in ultrasonic thickness measurement is the possibility that the instrument will use the
second rather than the first echo from the back surface of the material being measured. This may result in
a sound-velocity reading that is HALF what it should be.
Responsibility for proper use of the instrument and recognition of this phenomenon rests solely with the user
of the instrument.
Other errors may occur from measuring coated materials where the coating is insufficiently bonded to the
material surface. Irregular and inaccurate readings may result. Again, the user is responsible for proper use
and interpretation of the measurements acquired.
6.1 BEFORE YOU START
• Prepare the surface - see “Condition and Preparation of Surfaces” on page 24.
• Set the zero point of the transducer - see “Setting up the Gauge” on page 7.
• Select units; press to select metric (mm) or imperial (inches).
6.2 PROCEDURE
1. Apply couplant
For the gauge to work correctly there must be no air gap between the transducer and the surface of
the material to be measured. This is achieved using a couplant.
Before the transducer is placed on the surface, put a small amount of couplant on the surface of the
material. Typically a single drop is sufficient.
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2. Place transducer onto the surface of the material to be measured
Press the transducer wearface into the couplant. Moderate pressure on the top of the transducer using
the thumb or index finger is sufficient; it is only necessary to keep the transducer stationary and the
wearface seated flat against the surface of the material.
3. Read display
If six or seven bars of the stability indicator are showing, the display will be reading the correct sound-
velocity of the material directly beneath the transducer.
If the stability indicator has fewer than five bars showing, or the numbers on the display seem erratic,
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.
The gauge will perform a number of measurements every second when the transducer is in contact
with the surface of the material. The display is updated as each reading is taken.
4. Remove transducer from surface
The display will show 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 can
be seen when one sound-velocity value is observed while the transducer is in place, and another value is
observed after the transducer is removed. If this happens, take the reading again using less couplant.

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7 SCAN MODE
In normal operation, your gauge performs and displays four measurements every second, which is quite
adequate for taking a measurement at a single point.
It is sometimes desirable however to examine a larger region, searching for the thinnest point. Your gauge
includes a feature, called Scan Mode, which allows it to do just that.
In Scan Mode, the gauge performs 16 measurements every second, but does not display them, instead the
display shows a moving series of dashes.While the transducer is in contact with the material being
measured, the gauge memorises the lowest measurement it finds. The transducer can 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 one second the gauge will display the lowest value it found.
To switch Scan Mode on/off:
When the gauge is not in calibration mode, press the arrow. A message will appear briefly in the
display confirming the operation.
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8 STORAGE
Your gauge has a Liquid Crystal Display. If the display is heated above 50°C (120°F) it may be
damaged. This can happen if the gauge is left in a car parked in strong sunlight.
Always store the gauge in its case when it is not being used.
If the gauge is to remain unused for long periods of time, remove the batteries and store them
separately. This will prevent damage to the gauge in the event of malfunction of the batteries.
9 MAINTENANCE
You own one of the finest velocity gauges in the world. If looked after, it will last a lifetime.
9.1 FAULTS
Your gauge is designed to give many years reliable service under normal operating and storage conditions.
The gauge does not contain any user-serviceable components. In the unlikely event of a fault, the gauge
should be returned to your local Elcometer NDT supplier or directly to Elcometer NDT. The warranty will be
invalidated if the instrument has been opened.
9.2 TRANSDUCER
The transducer will wear with repeated use. Transducer life depends on the number of measurements taken
and the manner in which readings are taken. To extend transducer life, always set the transducer down so
that it is perpendicular to the panel surface. Dragging the transducer along the surface will reduce the life
ofthe transducer. Replacementtransducers are available from your local Elcometer NDT supplier or directly
from Elcometer NDT.

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10 TECHNICAL SPECIFICATION
Measurement Rate Manual 4 readings per second
Scan mode 16 readings per second
Measuring Rangea
a. Measuring Range depends on material, surface conditions and the transducer selected.
Sound Velocity 1250 m/s to 10000 m/s (0.0492 in/µs to 0.3930 in/µs)
Thickness 0.63 mm to 500 mm (0.025” to 19.999”)
Measurement Resolution Sound Velocity 1 m/s (0.0001 in/µs)
Thickness 0.01 mm (0.001")
Velocity Calibration Range 1250 m/s to 10000 m/s (0.0492 in/µs to 0.3937 in/µs)
Weight (including batteries) 284 g (10 oz)
Dimensions (W x H x D) 63.5 mm x 114.3 mm x 31.5 mm (2.5” x 4.5” x 1.24”)
Gauge Operating Temperature -30°C to 50°C (-20°F to 120°F)
Case Aluminium case with gasket sealed end caps and waterproof
membrane keypad
Display 12.7 mm (0.5 “) high digits with LED backlight (on/off/auto).
Power Source Two 1.5 V AA alkaline or 1.2V rechargeable cells. Typically
operates for 200 hours on alkaline and 120 hours on
rechargeable cells(charger not included.)
Note: Alkaline batteries must be disposed of carefully to avoid
environmental contamination. Please consult your local
environmental authority for information on disposal in your
region. Do not dispose of any batteries in fire.