NDT NDT-710 User manual

NDTINTERNATIONAL, INC.
711 S. Creek Road [phone]
West Chester, PA 19382 FAX [phone]
www.ndtint.com E-mail: [e-mail]
Operating Instruction Manual
Revision 2
NDT-710 Ultrasonic Thickness Gauge

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NDT- 710 Ultrasonic Thickness Gauge
Operating Instructions Rev. 2
Table of Contents Page No.
Basic Introduction to Ultrasonic Thickness Gauging:
How Does It Work? ..................................................... 2
What Materials Can Be Measured? ........................... 3
Things To Consider .................................................... 4
Dual Transducers ....................................................... 5
The NDT-710 Thickness Gauge:
Specifications ............................................................. 6
Operation .................................................................... 7
Calibration .................................................................. 7
Using A Special Application Transducer and
Sensitivity Adjustment ...................................... 8
Battery replacement .................................................... 9
Maintenance ............................................................... 10
Optional Accessories .................................................. 10
Velocity and Conversion Table ........................................... 11
Thickness Reference Blocks ............................................... 12
Warranty ................................................................................ 13

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A Basic Introduction to Ultrasonic Thickness Gauging
Ultrasonic thickness gauging is a widely used technique for measuring the thickness of a
material from one side. The first commercial ultrasonic gauges, using principles derived from
sonar, were introduced in the late 1940's. Small portable instruments dedicated to a wide
variety of applications became common in the 1970's.
Sound energy can be generated over a broad frequency spectrum. Audible sound, for example,
is restricted to a low frequency range with a typical upper limit of twenty thousand cycles per
second (or 20 Kilohertz or KHz). Ultrasound is sound beyond the limit of human hearing;
frequencies that are too high to be detected by the human ear. Thickness gauges for industrial
use operate at frequencies in the Megahertz range, typically from 1 to 20 MHz.
Ultrasound at high frequencies, because of the very short wave-length, has the advantage that it
can be used to make very accurate thickness measurements on most engineering materials.
Even more important, measurements can be made from one side only as the ultrasound waves
inside a material will bounce back from the opposite surface (like an echo). Thus thickness
measurements can be made instantly and accurately when the other side of the test part is
impossible or difficult to reach, with no need to cut parts for access. Ultrasonic thickness
measurements will save material, time, and labor costs.
HOW DOES IT WORK?
All ultrasonic measurements require two components: an electronic device (the gauge itself)
and an ultrasonic transducer. In order to make a thickness measurement the gauge transmits a
pulse of electrical energy to the transducer, which then converts this energy into high frequency
sound waves. This ultrasound enters the test material at the point of contact and propagates
through the material until it reflects from the opposite surface. Some reflected sound will travel
back to the point of entry, where it’s detected by the same transducer. In essence, the
transducer listens for the echo from the opposite side. In turn, the transducer converts sound
energy into electrical energy. The electronic circuitry of the gauge then precisely measures the
time interval between the initial pulse (or reference pulse) and the echo from the back wall.
Typically, this time interval is a few millionths of a second. The gauge computes actual
thickness of the test material by multiplying the time interval by the speed of sound in the
material and then dividing this by two in order to compensate for the round-trip transit time.
It is important to note that the velocity of sound in the test material is an essential part of this
computation. Different materials transmit sound at different velocities, and the sound velocity in
some materials will change significantly with temperature or composition. Therefore it is always
necessary to calibrate an ultrasonic instrument to the speed of sound of the test material at
hand. Accuracy of a measurement will be only as good as this calibration.

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It is practically impossible to efficiently transmit ultrasound from the transducer to the object to
be measured without the aid of a suitable coupling medium, usually referred to simply as
couplant. Couplants frequently used for thickness gauging are water, oil, gel, glycerin, and
propylene glycol. In practice, a small amount of couplant is applied between the transmitting
face of the transducer and the test surface.
WHAT MATERIALS CAN BE MEASURED?
Virtually any engineering material can be measured ultrasonically. Ultrasonic thickness gauges
can be set up for metals, plastics, ceramics, composites, epoxies, and glass. Liquid levels and
biological samples can also be measured. Materials generally not suited for conventional
ultrasonic gauging include wood, paper, concrete, and foam products. Online or inprocess
measurement of extruded plastics or rolled metal is often possible, as are layers or coatings in
multi layer materials.
THINGS TO CONSIDER
For any ultrasonic gauging application, the choice of gauge and transducer will depend on the
material to be measured, thickness range and accuracy requirements, geometry and
temperature, and any special conditions that may be present. Listed below, in order of
importance, are brief descriptions of some of the conditions that should be considered.

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Materials
Material is the most important determinant in final selection of gauge and transducer. Certain
materials, including most metals, glass, and ceramics, are excellent for sound propagation and
lend themselves to a wide range of measurement modes and transducer frequencies.
Other materials, such as plastics, absorb ultrasound more quickly and have a limited
measurable maximum thickness range. They are generally measured with gauges that utilize
contact type transducers. Rubber, fiberglass, and composites are even more attenuating and
often require gauges with special high penetration pulser/receivers and low frequency
transducers.
Thickness
Thickness ranges will also dictate the type of gauge and transducer to be selected. In general,
thin materials require high frequency transducers and thick or attenuating materials require
lower frequencies. Very thin material may not be within the range of a gauge utilizing contact
transducers; a delay line transducer may then be the answer. Similarly, gauges with delay line
and immersion transducers have limited maximum thickness capabilities primarily due to
potential interference from a multiple of the interface echo.
Geometry
A contract transducer is preferred for most ultrasonic measurements, unless sharp curvature or
small part size makes contact measurements impractical. As the surface curvature of the test
piece increases, the coupling efficiency from the transducer to the test piece is reduced. In
general, as the surface curvature increases, the size of the contact transducer should be
reduced. Extreme curvature or inaccessibility of the test surface requires a system with a delay
line or an immersion transducer.
Temperature
Contact transducers can be safely used on material surfaces up to 120 F (50 C). Thickness
measurements with contact transducers on material surfaces in excess of these temperatures
will result in transducer failure. Transducers with special heat resistant delay lines are
recommended on hot or warm surfaces above +180 F.
Accuracy
It should be considered that many factors may affect accuracy: sound attenuation and
scattering, sound velocity variations, poor coupling, surface roughness, non-parallelism,
curvature, echo polarity, etc. Selection of the best possible combination of gauge and
transducer should take into account all these factors. With proper calibration, measurements
can usually be made to an accuracy of 0.001 inch or 0.01 mm.

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Dual Transducers
The most common application for thickness measurements involves "dual" or "pitch-catch"
transducers. This is the type used with the NDT-710 thickness gauge. These employ separate
transmitter and receiver transducer elements mounted on a delay line. The two-transducer
elements are slightly angled towards each other, creating a “V” shaped sound path beneath the
surface of the part. Although measurement with dual transducers is not as accurate as with
other types of measurements, they provide better performance on rough or corroded surfaces
as found in pipelines, storage tanks, pressure vessels, structural support beams, and most
other metal components exposed to the weather and extremes in temperature, pressure and
humidity.

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Specifications:
The NDT-710 Ultrasonic Thickness Gauge is a Pulse/Echo type ultrasonic instrument that
uses a hand held dual element transducer to measure the thickness of metallic and nonmetallic
materials.
Measurement Range: 0.030 to 19.999 inches in carbon steel. This is dependent upon
the transducer used and the material measured. The standard kit
transducer will read to a minimum of 0.040"
Resolution: ± 0.001" (± 0.01 mm) up to 1.000 inches (25.3 mm)
± 1% from 1.000 to 19.999 inches
Velocity: 0.0197 to 0.3936 in/µ second (500 to 10,000 m/s)
V-Path Correction: The microprocessor automatically adjusts for linearity
Display: 4 ½ digit LCD display
Backlit Display: Set to "AU" - will light when transducer is coupled to material,
and will to shut off automatically after 10 seconds of non use.
Set to "ON" - backlight will come on when gauge is turned on
and remain on until gauge shuts off.
Set to "OFF" - backlight will remain off.
Temperature Range: +10 to +120F (-10 to +50C)
Size: 1.4" H. x 3.1" W. x 5.7" L.
Weight: 11 ounces
Features:
Automatic Zero adjust circuit for fast calibration
Automatic shut-Off 2 minutes last measurement or key pressed
Retains the last reading in memory
Battery life is approximately 75 hours continuous use from one 9 volt alkaline battery
with backlight turned OFF
Low battery level indicator in display
Coupling indicator
The backlit display liquid crystal display (LCD) gives easy-to-see thickness
readings in most lighting conditions
Keypad has built-in 0.250" thick calibration block
The standard kit includes the NDT-710 gauge, a 0.25" element diameter (.41" contact
face diameter) x 5.0 MHz dual element transducer with comfort grip housing on 4-foot
long top-exiting cable with LEMO #00 plug connectors, a 4 oz. bottle of top quality
ultrasonic couplant, operation manual and a padded accessory bag.

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Operation
1) Connect the dual element transducer to the connector sockets at the top of the
gauge.
2) Turn the NDT-710 gauge on by pressing the ON/OFF key at the upper left of the
keypad. If the gauge has already been calibrated it will display the last reading
taken; otherwise the gauge will display "PROB" (problem). When this appears
proceed with the Zero Calibration Procedure. The "PROB" indicator will also be
displayed when the NDT-710 is turned on after installation of a new battery and
may indicate a battery connection or a probe cable problem.
Power will remain on for approximately two (2) minutes after the last thickness
reading is taken of from the last key is pressed.
3) Couple the transducer to the calibration block using an acceptable couplant material.
The coupling indicator ( : ) turns off when the transducer is properly coupled to
the test piece.
4) Apply pressure to hold the transducer flat against the surface of the calibration
block or test piece.
5) Observe the thickness reading at the point where the transducer is in contact with
the calibration block or test piece.
6) Use the (INCH / MM) key to switch between inch (19.999 max) and millimeter
(199.99 max) units.
Note: Always clean and apply couplant to all surfaces to be measured.
Large deposits of couplant remaining on the transducer may cause an erratic
display when the transducer is not coupled to the product.
Zero Calibration Procedure
This procedure must be performed every time the transducer is changed, whether the
replacement is the same type or not. This Zero calibration will compensate for the
varying thickness of the delay line built into every dual element transducer.
1) Connect the transducer to the NDT-710 Gauge and press the (ON / OFF) key.
2) Make sure the surface of the calibration disk on the panel is clean.
3) Apply a thin layer of ultrasonic couplant to the calibration disk.
4) Press the (CAL) key: (CAL) will appear on the LCD display.
5) Couple the transducer to the calibration disk with steady pressure, and hold until the
LCD displays ( - - - - ). Once this display appears the gauge is calibrated and is
ready to measure carbon steel material.

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Calibration to a Known Thickness
To measure materials other than carbon steel follow this procedure. A calibration standard of
the same material and of known thickness is required. For best results, the thickness should be
equal to or slightly greater than the thickness of the part to be measured. The standard Zero
Calibration step, explained previously, must be done prior to this calibration.
1) Apply a thin layer of couplant to the calibration standard. Place the transducer on the
standard and make sure the reading is stable. The reading obtained will not
necessarily match the known thickness of the calibration standard.
2) Uncouple the transducer from the same and use the UP (▲) or DOWN ( ▼) keys to
adjust the LCD display until it shows the same thickness as the sample block.
3) You are now ready to measure. This adjustment is saved in memory and will not
change until the Zero Calibration step is repeated.
Using A Special Application Transducer - Sensitivity Adjustment
When using other than the standard transducer provided with the NDT-710 gauge it may
be necessary to make an adjustment to the sensitivity pot. This adjustment may be
necessary when using these special application transducers:
Part No. 710-2HT High Temperature Transducer
710-3 Low Range Transducer
710-4 High Power Transducer
710-7 Small Diameter, Higher Resolution Transducer
710-8 Pencil Type Transducer
It should not be necessary when using these transducers:
Part No. 710-1 Standard Transducer
710-1HT High Temperature Transducer
710-5 Small Contact Diameter Transducer
710-6 Low Profile Transducer
Sensitivity adjustment is performed as follows:
1) Connect the transducer to the gauge and turn gauge ON.
2) Remove the small black cap located to the right of the transducer connectors at
the top of the gauge.
3) Locate the small slotted pot just inside the case.
4) Using a small screwdriver, turn the pot full Counter Clockwise (CCW).
NOTE: Full movement of this pot is about ¾ of a turn.
5) With the transducer on the gauge keypad 0.250" calibration block, push (CAL).

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6) Observe that the display shows ( : CAL ).
7) Turn the sensitivity adjustment pot gradually, in a Clockwise (CW) direction, until the
display changes to ( - - - - ), which indicates proper calibration of the transducer
to the gauge.
8) Place the transducer on various other known thickness samples to verify the
transducer measurement range. It may be necessary to make a fine adjustment
CCW or CW to obtain the maximum correct range.
9) Once set, replace the small black cap. The gauge will then be calibrated for
optimum accuracy and range for that transducer.
LCD Display Backlight
1) To turn on the backlight press the (CAL) key and the up arrow key (▲) at the same
time. (OFF) will appear in the display signifying that the backlight is off.
2) While holding (CAL), press (▲) again and (ON) will appear signifying that the
backlight is on continuously.
3) Press (▲) again and (AU) will appear in the display signifying that the backlight in
automatic mode. In this mode the backlight will come on when the transducer is
coupled to material and will to shut off automatically after 10 seconds of non-use.
This mode will extend battery life.
Battery Replacement
1) The Low Battery indicator is a small arrow ( ←) which will appear in the upper
left of the display window, above the coupling indicator. This lights when the
battery drops below the proper operating level.
2) The battery should be replaced within two hours after the indicator lights. If not,
the readings can become unreliable.
3) Slide the battery cover on the bottom of the shell to the rear.
4) Remove battery holder from battery compartment and remove old battery.
5) Insert new 9VDC battery observing proper polarity. Reversed batteries may
cause permanent damage.
NOTE: Some older gauges used (4) "AAA" batteries.
6) Install the battery cover.
ALWAYS CARRY A SPARE BATTERY.

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Maintenance
1) DO NOT WRAP THE TRANSDUCER AROUND THE GAUGE. This will damage
the LEMO connector sockets.
2) Check the transducer cable regularly for cuts or abrasions and that connectors are
securely attached.
3) The LCD is made of glass and may break if the gauge is dropped. Be careful.
4) Keep the gauge clean. DO NOT clean the gauge with any solvents or abrasives.
Use a mild glass or window cleaner applied with a soft rag.
Optional Accessories:
Nylon Instrument Case with Neck and Wrist Straps Part No. 710-IC
Replacement Padded Nylon Carry Bag Part No. 710-CC
Transducers:
Standard 0.25" element diameter (.41" contact area) x 5.0 MHz provides a
measurement range of 0.040" to 12.000" Part No. 710-1
High Temperature 0.25" element diameter (7/16" contact diameter) x 5.0 MHZ
transducer - for temperature use up to 500 oF (260 oC),
provides a measurement range of 0.150" to 6.000" Part No. 710-1HT
High Temperature 0.50" element diameter (0.63" contact diameter) x 2.25 MHz
transducer - for temperature use up to 500 oF (260 oC),
provides a measurement range of 0.150" to 6.000" Part No. 710-2HT
Low Range 0.25" element diameter (0.38" contact diameter) x 7.5 MHz transducer
provides a measurement range of 0.030" to 2.000" Part No. 710-3
High Power 0.50" element diameter (0.62" contact diameter) x 2.25 MHz transducer
provides a measurement range of 0.200" to 10.000" Part No. 710-4
Small Diameter 0.18" element diameter (0.25" contact area) x 5.0 MHz transducer
provides a measurement range of 0.040" to 2.000" Part No. 710-5
Low Profile, same as P/N 710-1, but with side exiting cable Part No. 710-6
Small Diameter/High Resolution 0.18" element diameter (0.25" contact area)
x 7.5 MHz transducer (range of 0.030" to 2.000") Part No. 710-7
Pencil Type, 0.25" element dia. x 5.0 MHz (0.38" contact diameter), 0.040"
to 6.000" range, in 3" long housing Part No. 710-8
Reference blocks (traceable to NIST), nickel-plated steel:
4-step (0.250" to 1.000") Part No. 4SB
5-step (0.100" to 0.500") Part No. 5SB
6-step (0.040", 0.100" to 0.500") Part No. 6SB
Also available in 7075 aluminum or 304 stainless steel and in metric dimensions
Ultrasonic Couplant:
4 oz. or 12 oz. plastic squeeze bottles, ULTRAGEL-II (-10 to +210 F.) in cases of one
dozen bottles per case or by the gallon in collapsible plastic container.
High temperature couplants (+600 and +900 F.) available in 4 oz. tubes only

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VELOCITY and CONVERSION FACTOR TABLE
Longitudinal Velocity Conversion Factor
Material Inch/µSec mm./µsec from Mild Steel
ALUMINUM .248 6.32 0.93
BERYLLIUM .507 12.9 0.45
BRASS .169 4.28 1.36
CADMIUM .109 2.78 2.11
CAST IRON .189 4.80 1.22
COPPER .183 4.66 1.26
DIAMOND .690 17.5 0.33
GLASS (Crown) .207 5.26 1.11
GLASS (Window) .267 6.79 0.86
GLYCERIN .076 1.92 3.03
GOLD .128 3.24 1.80
INCONEL .225 5.72 1.02
IRON .232 5.90 0.99
IRON (Cast) .189 4.80 1.22
LEAD .087 2.16 2.64
LUCITE .106 2.68 2.17
MAGNESIUM .248 6.31 0.93
MANGANESE .183 4.66 1.26
MOLYBDENUM .248 6.29 0.93
MONEL .237 6.02 0.97
NEOPRENE .063 1.60 3.65
NICKEL .222 5.63 1.04
NYLON 6, 6 .066 1.68 3.48
OIL (SAE 30) .685 1.74 0.34
PHENOLIC .559 1.42 0.41
PLATINUM .156 3.96 1.47
PLEXIGLAS (UVA) .109 2.76 2.11
PLEXIGLAS (UVA II) .107 2.73 2.15
POLYETHYLENE .105 2.67 2.19
POLYSTYRENE .105 2.67 2.19
POLYURETHANE .070 1.90 3.28
PORCELAIN .220 5.60 1.04
RUBBER (Butyl) .073 1.85 3.15
RUBBER (Vulcanized) .090 2.30 2.55
SILVER .142 3.60 1.62
STEEL (Mild) 4340 .233 5.85 1.00 (Factory Standard)
STAINLESS STEEL .225 5.80 1.02
TIN .131 3.32 1.76
TITANIUM .239 6.07 0.96
TUNGSTEN .204 5.18 1.13
WATER .584 1.48 0.39
ZINC .164 4.17 1.40
ZIRCALOY 2 .187 4.65 1.23
EXAMPLE: At factory setting, the NDT-710 Thickness Gauge reads 0.630" when measuring a
copper plate. Since the velocity of copper is less than that of steel, the actual thickness would be
less than the gauge display reading. Finding the appropriate material in the above table and
dividing the gauge reading by the conversion factor (1.26 for Copper) will convert the reading to
the actual material thickness. 0.630” divided by 1.26 = 0.500" (the Actual Thickness)

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5-Step Steel Thickness Calibration Block (Typical)
Note: The typical thickness reference block is supplied in Ni-plated C1018 steel
and is also available in 7075 Aluminum and 304 Stainless Steel.
A Metric version is also available in 2.5 mm steps in a thickness range
of 2.5 mm to 12.5 mm.

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Equipment Warranty
1. Electronic instrumentation manufactured by NDT International Inc. is warranted to be free
from defects in workmanship and material under normal use and service for a period of
one year from the date of shipment unless otherwise specified.
2. Instrumentation purchased from outside sources, to meet customer's special requirements,
is guaranteed by the original manufacturer's warranty only.
3. Ultrasonic transducers and angle beam wedges (shoes) are not covered by the standard
equipment warranty. Transducers are considered an expendable item, can be easily
damaged through misuse or exposure to extreme temperatures and can be worn out
through use on excessively rough surfaces. If transducers experience failure within the
first thirty days, and have not been exposed to excessive use, replacement will be
considered after examination by NDT International.
4. Warranty repairs are accomplished by NDT International or our authorized representative.
5. Goods or parts that are defective in workmanship and/or material will be repaired or replaced
free of charge, FOB authorized repair station, provided that the goods or parts are
returned, transportation charges prepaid, within the specified warranty period.
6. Materials returned for warranty repairs must have prior authorization. Obtain a Return
Material Authorization (RMA) number from NDT International or our authorized
representative prior to shipment. The RMA number must be used on all correspondence
and packing lists.
7. Ship prepaid to the address below, ATTN: Quality Assurance Mgr. - Repairs
8. Warranty repairs include all parts and labor. The cost of any travel and/or subsistence to
accomplish on-site warranty repairs, if requested by purchaser, is not a warranty item
and will be charged to the purchaser in accordance with normal company procedure.
9. The cost of repairing goods damaged during shipment is not covered by this warranty
unless specific allowances are made prior to shipment.
For service, repairs or calibration contact NDT at the following address:
NDTINTERNATIONAL, INC.
711 S. Creek Road
West Chester, PA 19382-8013 U.S.A.
Phone: [phone] FAX: [phone]
E-Mail: [email protected]

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NOTES and COMMENTS