ABQINDUSTRIAL TI-25MX User manual

MODEL TI-25MX
ULTRASONIC THICKNESS GAUGE
Operating Manual
Distributed by: ABQ Industrial LP USA
Tel: [phone] eFax: [phone]
Web: https://www.abqindustrial.net E-mail: [email protected]

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TABLE OF CONTENTS
1.0 Introduction .......................................................................................................................... 01
1.1 Disclaimer......................................................................................................................
2.0 Keypad, Menu, Display & Connectors ............................................................................... 03
2.1 ON/OFF/ENTER Key0
2.2 PRB 0 Key
2.3 CAL Key
2.4 GAIN Key
2.5 SCANKey
2.6 +/- INCREMENT/DECREMENT Keys
2.7 MATL Key….
2.8 MENU Key…
2.9 The Display
2.10 The Transducer
2.11 Top End Cap
3.0 Principals of Ultrasonic Measurement ............................................................................... 9
3.1 Time versus thickness relationship
3.2 Suitability of materials
3.3 Range of measurement and accuracy
3.4 Couplant
3.5 Temperature
3.6 Measurement modes
4.0 Selecting the measurement mode........................................................................................ 12
4.1 Which Mode and Transducer do I use for my applications?
5.0 Making measurements ......................................................................................................... 14
5.1 Probe Zero
5.2 Material Calibration
6.0 Additional features ............................................................................................................... 20
6.1 GAIN
6.2 Hight-speed Scan
6.3 Unit
6.4 Lite
6.5 Zero
6.6 Probe Diameter
6.7 Lock
6.8 Factory Defaults
7.0 Appendix A - Velocity Table................................................................................................. 25
8.0 Appendix B- Application Notes ........................................................................................... 26
9.0 Warranty ............................................................................................................................... 28

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1.0 INTRODUCTION
The Checkline model TI-25MX is a basic dual element thickness gauge with the ability
to locate blind surface pitting and internal defects/aws in materials. Based on the same
operating principles as SONAR, the TI-25MX is capable of measuring the thickness
of various materials with accuracy as high as ± 0.001 inches, or ± 0.01 millimeters.
The principle 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 Disclaimer
Inherent in ultrasonic thickness measurement is the possibility that the instrument will
use the second rather than the rst echo from the back surface of the material being
measured. This may result in a thickness reading that is TWICE what it should be.
Responsibility for proper use of the instrument and recognition of this phenomenon rest
solely with the user of the instrument. Other errors may occur from measuring coated
materials where the coating is insufciently 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.

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2.0 KEYPAD, MENU, DISPLAY & CONNECTORS
The Keypad
2.1 ON/OFF/ENTER Key
The ON/OFF/ENTER key powers the unit ON or OFF. Since the same key is
also used as an ENTER key, the gauge is powered off by pressing and holding
down the key until the unit powers off.
Once the gauge is initially powered on, this key will function as the ENTER key, similar
to a computer keyboard. This key will be used to select or set a menu option.
NOTE: Unit will automatically power off when idle for 5 minutes. All current settings
are automatically saved prior to powering off.
2.2 PRB 0 Key
The PRB 0 key is used to “zero” the TI-25MX in much the same way that a
mechanical micrometer is zeroed. If the gauge is not zeroed correctly, all of the
measurements that the gauge makes may be in error by some xed value. Refer
to section 5.1 for a further explanation of this important feature.
2.3 CAL Key
The CAL key is used to enter and exit the TI-25MX’s calibration mode. This
mode is used to adjust the sound velocity value that the TI-25MX will use when
calculating thickness. The tool will either calculate the sound-velocity from a
sample of the material being measured, or allow a known velocity value to be entered
directly. This provides increased linearity between transducers. Refer to section 5.2 for
an explanation on the various calibration options.

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2.4 GAIN Key
The TI-25MX has an adjustable gain feature for additional versatility to control
the overall output of the gauge, to compensate for various materials and
applications. There are ve gain settings (VLOW, LOW, MED, HIGH, VHI).
The gain range is 40dB – 52dB in 3dB increments. Refer to section 6.1for
details regarding the GAIN feature.
2.5 SCAN Key
The TI-25MX offers a high speed scan feature. This feature allows for
scanning larger areas on a given test material, while still offering reasonable
representation of thickness over the area scanned. Refer tsection 6.2 for an
explanation on the scan feature.
2.6 +/- Increment/Decrement Key’s
The +/- Keys are used to increment/decrement values,
navigate menus, and select menu options.
2.7 MATL Key
The MATL Key is used to select a common basic material type from a short list
of 9 materials and 2 programmable custom materials for calibration. Refer to
section 4.1 for an explanation on selecting a basic material type.
2.8 MENU Key
The MENU key is used to access and set all of the additional features of the
TI-25MX that are not at the top level of the keypad with a dedicated key. The
features and setting are outlined below:
Menu Feature Items
Unit Lite Zero Probe
English On Manual .187
Metric Off Auto .250
Options .500
Lo
Med
High

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Here’s a quick overview of navigating through the various features in
MENU:
1. Press the MENU key once to enter the sub menu items
2. Press the +and –keys to toggle through the features.
3. To enable or edit the status of any feature, press the ENTER key.
4. The edit icon will start blinking to indicate that the TI-25MX is currently in EDIT
mode.
5. Press the +and –keys to toggle through the setting options.
6. Press the ENTER key to accept changes and return to the top level of features,
or the MENU key at any time to abort changes and return the measurement screen.
2.9 The Display
The TI-25MX uses a custom glass
LCD backlit low temperature display
for use in a variety of climate
conditions. It contains graphic icons,
as well as both 7 and 14 segment
display areas. Let’s take a closer
look and what all these things are
telling us:
NOTE: This display is used for
multiple gauge models in the
TI series. As a result, some of
the icons and segments that are
illuminated during boot up, may not be applicable to your specic model, and will never
be illuminated during operation. The icons and segments that will be used with the
TI-25MX are shown in the diagram above.
A. Edit: This icon will be displayed, and blinking, to let a user know when they are in
an edit mode to change a value or setting.
B. Large 7 segment: The thickness measurement, velocity or alpha message will be
displayed in this area.
C. Measurement Modes: This icon indicates the measurement mode. The TI-25MX
operates exclusively in pulse-echo (P-E) mode only.
D. Stability/Repeatability Indicator: This is used in conjunction with the thickness
measurement as a reference for the validity of the measurement. The TI-25MX
takes multiple measurements per second, and when all the vertical bars are
illuminated, it’s a reference that the same thickness value is reliably being measured
multiple times per second.
E. Battery: Indicates the amount of battery life the TI-25MX has remaining.
F. Backlight : When this icon is illuminated, it indicates the backlight is on.

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G. Small 7 Segment: The material velocity, speed the sound wave travels through a
given medium/material, is displayed in this area, informing the user what material
the TI-25MX is currently calibrated too. This area is also used for alpha messages
in the menu and edit modes.
H. Units: This combination of icons are illuminated in different sequences to inform
the user what measurement units are currently being displayed in the small 7
segment area.
I. Small 14 Segment: Displays the current gain setting of the TI-25MX. MED is the
default, with the options of VLOW, LOW, MED, HIGH, VHI (40dB to 52db gain
range with MED at 46dB).
J. Units: This combination of icons are illuminated in different sequences to inform
the user what measurement units are currently being displayed in the large 7
segment area.
K. Small 14 Segment: The material type is displayed in this area. If it is set to a
value of one of the materials in our material list, it will be displayed in alpha
characters indicating the material type. Otherwise it will be set to CUST, indicating
custom material type.
L. Features: The icons illuminated in this row across the bottom of the LCD display
which features are currently enabled. For a complete list of the menu features in
the TI-25MX, Refer to section 2.0 for a list. The TI-25MX can be locked once
calibrated, to avoid accidently changing the calibration. When this icon is
illuminated, the TI-25MX is in lock mode. Refer section 6.7 for an explanation on
locking the TI-25MX.
2.10 The Transducer
The transducer is the “business end” of the TI-25MX. It transmits and receives
ultrasonic sound waves that the TI-25MX uses to calculate the thickness of the material
being measured. The transducer connects to the TI-25MX via the attached cable, and
two coaxial connectors. When using transducers manufactured by Checkline, the
orientation of the dual coaxial connectors is not critical: either plug may be tted to
either socket in the TI-25MX.
The transducer must be used correctly in order for the TI-25MX to produce accurate,
reliable measurements. Below is a short description of the transducer, followed by
instructions for its use.

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This is a bottom view of a typical transducer. The two semicircles of the wear face
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 wear face that is being measured.
This is a top view of a typical transducer. Press against the top with the thumb or index
nger to hold the transducer in place. Moderate pressure is sufcient, as it is only
necessary to keep the transducer stationary, and the wear face seated at against the
surface of the material being measured.
Measuring
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” uid, commonly called “couplant”. This uid 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 sufcient.
After applying couplant, press the transducer (wear face down) rmly against the area
to be measured. The Stability Indicator should have six or seven bars darkened, and a
number should appear in the display. If the TI-25MX has been properly “zeroed” (see
page 14) and set to the correct sound velocity (see page 16), the number in the display
will indicate the actual thickness of the material directly beneath the transducer.
If the Stability Indicator has fewer than ve bars darkened, or the numbers on the
display seem erratic, rst check to make sure that there is an adequate lm of couplant
beneath the transducer, and that the transducer is seated at against the material. If the
condition persists, it may be necessary to select a different transducer (size or frequency)
for the material being measured. See page 12 for information on transducer selection.

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While the transducer is in contact with the material that is being measured, the TI-25MX
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.
2.11 Top End Cap
The top end cap is where all connections are made to the TI-25MX. The diagram above
shows the layout and description of the connectors.
Transducer Connectors
Refer to Diagram: The transducer connectors and battery cover/probe zero disk are
located on the TI-25MX’s top end cap. The transducer connectors are of type Lemo
“00”.
NOTE: There is no polarity associated with connecting the transducer to the TI-25MX,
it can be plugged into the gauge in either direction.
Probe Zero Disk & Battery Cover
Refer to Diagram: The Battery cover is the large round disk shown in the diagram.
NOTE: This same disk is also used as a probe zero reference disk. Simply remove the
cover when replacing the batteries (2 AA cells). When performing a manual probe zero
function, simply place the transducer on disk making rm contact. Important: Be sure
the battery polarity is correct, which can be found on the back label of the TI-25MX.
NOTE: Rechargeable batteries can be used, however they must be recharged outside of
the unit in a standalone battery charger.

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3.0 PRINCIPALS OF ULTRASONIC MEASUREMENT
3.1 Time versus thickness relationship
Ultrasonic thickness measurements depend on measuring the length of time it takes for
sound to travel through the material being tested. The ratio of the thickness versus the
time is known as the sound velocity. In order to make accurate measurements, a sound
velocity must be determined and entered into the instrument.
The accuracy of a thickness measurement therefore depends on having a consistent
sound velocity. Some materials are not as consistent as others and accuracy will be
marginal. For example, some cast materials are very granular and porous and as a result
have inconsistent sound velocities.
While there are many different ultrasonic techniques to measure thickness, which will
be discussed below, all of them rely on using the sound velocity to convert from time to
thickness.
3.2 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 difcult include some cast materials, concrete, wood, berglass,
and some rubber.
3.3 Range of measurement and accuracy
The overall measurement capabilities, based on the wide variety of materials, is
determined by the consistency of the material being measured
The range of thickness that can be measured ultrasonically depends on the material type
and surface, as well as the technique being used and the type of transducer. The range
will vary depending on the type of material being measured.
Accuracy, is determined by how consistent the sound velocity is through the sound path
being measured, and is a function of the overall thickness of the material. For example,
the velocity in steel is typically within 0.5% while the velocity in cast iron can vary by
4%.
3.4 Couplant
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 frequencies used in ultrasonic thickness measurement do not travel through air
efciently. By using a liquid couplant between the transducer and test piece the amount
of ultrasound entering the test piece is much greater.

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3.5 Temperature
Temperature has an effect on sound velocity. The higher the temperature, the slower
sound travels in a material. High temperatures can also damage transducers and present
a problem for various liquid couplants.
Since the sound velocity varies with temperature it is important to calibrate at the same
temperature as the material being measured.
Normal temperature range
Most standard transducers will operate from 0°F to 250°F.
High temperature measurements
Special transducers and couplants are available for temperatures above 250°F up to
1000°F with intermittent contact. It is necessary to cool the transducer by submerging it
in water between measurements.
Modes and temperature errors
In addition to errors caused by velocity changing with temperature, some modes
(measurement techniques) are affected more than others. For example, dual element
pulse-echo mode has larger errors due to changes in the temperature of the transducer.
However, multi-echo techniques offer temperature compensation help to minimize these
errors.
3.6 Measurement Modes
This section will cover the different measurements modes of the TI-25MX, the
transducers required, and the reasons for using specic modes:
Pulse-Echo (P-E) Mode:
Pulse-echo mode measures from the initial pulse (sometimes referred to as an articial
zero) to the rst echo (reection). In this mode, either an automatic or manual zero
can be performed depending on the zero probe setting. If the manual mode has been
selected, the transducer is placed on the reference disk located on top of the TI-25MX,
and the PRB 0 key pressed to establish a zero point for the transducer connected. If the
Auto Zero feature is enabled, simply pressing the PRB 0 key will perform an electronic
zero to establish the same zero point.
In pulse-echo mode, errors can result from surface coatings and temperature variations.
Since pulse-echo only requires one reection, it is the most sensitive mode for
measuring aw/defects when measuring heavily corroded metals.
V-Path Correction
Dual element delay line transducers have two piezoelectric elements focused towards
one another at a slight angle, mounted on a delay line. One element is used for
transmitting sound, while the other element receives the sound reection. The two

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elements and their delay lines are packaged in a single housing but acoustically isolated
from each other with an insulated sound barrier. This allows the transducer the ability
to achieve very high sensitivity for detecting small defects. Also, the surface of the test
material does not have to be as at in order to obtain good measurements.
Dual element transducers are normally used in pulse-echo mode for nding defects, and
in echo-echo mode for through coating measurements.
Dual element delay line transducers are have a usable range of 0.025” and up, depending
on the material, frequency, and diameter.
A limitation of dual element delay-line transducers is the V shaped sound path. Because
the sound travels from one element to another, the time versus thickness relationship
is non-linear. Therefore, a correction table in the instruments software is used to
compensate for this error.
Searching for small defects
Dual element delay line transducers are especially useful in searching for small defects.
In pulse-echo mode with high amplier gain, very small defects can be located. As a
result, this conguration is commonly used for corrosion inspections. The dual element
style transducer will nd wall deterioration, pits, cracks, and any porosity pockets
during tank and pipeline inspections.
Dual Element Transducer showing
V-path of signal

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4.0 SELECTING THE MEASUREMENT MODE
4.1 Which mode & transducer do I use for my application?
High penetration plastics and castings
The most common mode for these types of applications is pulse-echo. Cast iron
applications require 1 - 5MHz frequencies, and cast aluminum requires a 7 - 10MHz
frequency depending on the thickness. Plastics typically require lower frequencies
depending on the thickness and make-up of the material as well. Larger diameters offer
greater penetration power based on the size of the crystal.
Corrosion & Pit Detection in steel and cast materials
Pulse-echo mode is commonly used for locating pits and defects. Typically a 5MHz
transducer, or higher, will be used for these types of applications. Use low frequencies
for greater penetration and use higher frequencies for better resolution.
Measuring Material & Coatings
The pulse-echo coating mode should be used when both material and coating thickness
are required, while still requiring the ability to detect aws and pits. A special coating
style transducer is required for use in this mode. There are a variety of coating
transducers in various frequencies available from Electromatic.
Thru Paint & Coatings
Often times, users will be faced with applications where the material will be coated
with paint or some other type of epoxy material. Since the velocity of the coating is
approximately 3 times slower than that of steel, pulse-echo mode will result in an error
if the coating or paint is not completely removed.
Thin materials
Pulse echo mode and a high frequency transducer is commonly used for these types
of applications. The most common transducers are the 7.5MHz and 10MHz models
with extra resolution. The higher frequencies provide greater resolution and a lower
minimum thickness rating overall.

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High temperature
Special 5 MHz High temperature transducers are available for these types of
applications. Both pulse-echo and echo-echo modes will also work for these
applications. However, echo-echo mode will eliminate error caused by temperature
variations in the transducer.
Noisy Material
Materials such as titanium, stainless steel, and aluminum may have inherent surface
noise issues or mirroring effect. Higher frequency transducers 7 – 10MHz offer
improved resolution to avoid erroneous measurements.
Restricted access
Measuring materials with extreme curvatures or restricted access are best suited for
higher frequencies and smaller diameter transducers.

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5.0 MAKING MEASUREMENTS
The steps involved in making measurements are detailed in this section. The following
sections outline how to setup and prepare your TI-25MX for eld use.
An automatic or manual zero must always be performed. The auto zero is an ‘off block’
electronic zero that does not require a zero reference standard. This will most always be
the zero option of choice, as it makes the zeroing process very easy and convenient to
perform. However, the manual zero option offers better accuracy in terms of a reference
point. If the manual zero option is enabled, the probe zero must be measured on the
reference disk (battery disk) attached to the top of the instrument. The zero compensates
for variations in the transducer. In either mode the sound velocity must be determined,
and is used to convert the transit time to a physical length. The sound velocity can be
selected from a material chart in the manual, selected from a short list of common
materials in the TI-25MX, or for greater precision determined from a sample of the test
material that has been mechanically measured. To enter the velocity from a table, look
up the material on the chart in the appendix of this manual and refer to the section below
on Calibration to a Known Velocity. To determine the velocity of a single sample, refer
to the Material Calibration section in section 5.2.
When measuring curved materials, it’s more accurate to calibrate from two test points,
one at the minimum limit of the target thickness and one at the maximum limit. In this
case the reference disk mounted to the TI-25MX is not used. This is called two-point
calibration and is described section 5.2
5.1 Probe zero
Setting the zero point of the TI-25MX is important for the same reason that setting the
zero on a mechanical micrometer is important. It must be done prior to calibration, and
should be done throughout the day to account for any temperature changes in the probe.
If the TI-25MX is not zeroed correctly, all the measurements taken may be in error by
some xed value. The zero can only be performed with the measurement mode set to
pulse-echo (P-E). Therefore, if the TI-25MX is to use the echo-echo (E-E) measurement
mode and a manual zero is being performed, the TI-25MX will argue by briey
displaying the message “NO PRB0”.
IMPORTANT NOTE: The internal zero setting of the TI-25MX, used for the auto
zero mode, can be reset at anytime by performing a “manual zero”, and immediately
followed by performing an “auto zero”.
The TI-25MX is equipped with two zero options:
1. Off Block Zero (Automatic Probe Zero) – When this feature is enabled the
TI-25MX will do an electronic zero automatically, eliminating the need for a zero
disk or reference standard.

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2. On Block Zero (Manual Probe Zero) – When this feature is enabled the transducer
must be placed on the probe zero disk (battery cover) located on the top of the unit.
Both zero procedures are outlined as follows:
Performing an Auto Probe Zero (Off Block)
1. Be sure all couplant has been removed from the face of the transducer.
2. Press the key to perform the auto zero. “AUTO ZERO” will briey be
displayed on the screen, indicating the zero calculation is being
performed.
Performing a Manual Probe Zero (On Block)
NOTE: When the zero probe option is set to manual, the probe zero disk (battery cap)
located on the top of the gauge will be used as a zero standard.
1. Apply a drop of couplant on the transducer and place the transducer in
steady contact with the disk (battery cover) located at the top of the unit to obtain a
measurement.
2. Be sure all six repeatability/stability bars in the top left corner of the display are
fully illuminated and stable, and last digit of the measurement is toggling
only +/- .001” (.01mm).
3. Press the key to perform the manual zero. “PRB0” will briey be displayed
on the screen, indicating the zero calculation is being performed.
5.2 Material Calibration
In order for the TI-25MX to make accurate measurements, it must be set to the correct
sound velocity of the material being measured. Different types of materials have
different inherent sound velocities. For example, the velocity of sound through steel
is about 0.233 inches per microsecond, versus that of aluminum, which is about 0.248
inches per microsecond. If the gauge is not set to the correct sound velocity, all of the
measurements the gauge makes will be erroneous by some amount.
The One Point calibration is the simplest and most commonly used calibration method
—optimizing linearity over large ranges. The Two Point calibration allows for greater
accuracy over small ranges by calculating both the probe zero, as well as the material
velocity. The TI-25MX provides three simple methods for setting the sound-velocity
outlined on the following page:

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Known Velocity
If the material velocity is known, it can be manually entered into the TI-25MX, rather
than have the TI-25MX calculate the velocity value using a known thickness of the same
material type. The steps for entering the velocity are outlined below:
1. With the transducer free from contact with the material, press the key to
display the current velocity.
2. Use the and keys to scroll the velocity to the known target
value.
NOTE: The longer the keys are pressed and held, the faster the value will increment/
decrement.
NOTE: Pressing the key prior to pressing the key will abort the cal routine without
saving any changes.
3. Press the key to set the velocity value and return to the measurement
screen. The new velocity value will be shown at the top of
the display.
Known Thickness
Often times the exact sound velocity of a material is unknown. However, a sample
with one or two known thicknesses can be used to determine the sound velocity. As
previously discussed, the TI-25MX has a one or two point calibration option. The
one point calibration option is most suited for linearity over large ranges. When using
the one point option, the calibration should be perform on the thickest side of the
measurement range for the best linearity for that range. For example, if the measurement
range is .100” (2.54mm) to 1.0” (25.4mm), the user should calibrate on a known
thickness sample close to 1.0” (25.4mm). Note: It’s always handy to carry a set of
mechanical calipers to use in conjunction with the TI-25MX for calibration of various
materials in the eld:
One Point Calibration
NOTE: Be sure that a probe zero has been performed prior to performing this
calibration procedure.
1. Physically measure an exact sample of the material, or a location directly on the
material to be measured, using a set of calipers or a digital micrometer.
NOTE: A sample or location on the test piece should be used as close to the maximum
thickness of the test range to minimize error.
2. Apply a drop of couplant on the transducer and place the transducer in steady
contact with the sample or actual test material. 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. Press the key to enter the calibration edit screen displaying the current
measurement value.

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4) Use the and keys to scroll to the known thickness value.
NOTE: The longer the keys are pressed and held, the faster the value will increment/
decrement.
NOTE: Pressing the key prior to pressing the key will abort the CAL
routine without saving any changes.
5. Once the known thickness value is being displayed, press the key to display the
calculated material velocity edit screen.
NOTE: The calculated velocity can be edited, if needed, by pressing
the and keys to scroll and edit the velocity value.
6. Press the key to set the calculated material velocity and return to the
measurement screen.
CHECK YOUR CALIBRATION! Place the transducer back on the calibration point
and verify the thickness. If the thickness is not correct, repeat the steps above.
Two Known Thicknesses
The two point calibration should be considered when an application requires improved
accuracy over a small measurement range based on tolerance requirements. This
calibration option calculates both the ‘probe zero’ and ‘velocity value. If the two point
option is used, a probe zero is not required. For example, if the measurement range was
.080” (2.03mm) to .250” (6.35mm), two known samples or locations on the test material
would be needed for the minimum and maximum boundaries of the test range. Using the
range above, a one point calibration would be performed at .250” (6.35mm) and a two
point calibration at .080” (2.03mm), or something close to the min/max values of the
measurement range.
NOTE: The TI-25MX also offers the capability of setting the ‘probe zero’ to use any
reference standard as the ‘probe zero’ standard. For clarication, if it’s desired to use a
one inch reference of a specic material type as the ‘zero’ reference, performing the rst
point of a two-point calibration sets the internal zero of the TI-25MX. This should be
used only in manual probe zero mode “on block”.
The following steps outline this procedure:
Two Point Calibration
1. Physically measure a minimum and maximum calibration point of the exact sample
material, or locations directly on the material to be measured, using a set of calipers
or a digital micrometer.

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NOTE: A sample or location on the test piece should be used as close to the minimum
and maximum thickness of the test range to minimize error and improve linearity.
2. Apply a drop of couplant on the transducer and place the transducer in steady
contact with either the minimum or maximum sample or actual test material. 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. Press the key to enter the calibration edit screen displaying the current
measurement value.
4). Use the and keys to scroll to the known thickness
value.
NOTE: The longer the keys are pressed and held, the faster the value will increment/
decrement.
NOTE: Pressing the key prior to pressing the key will abort the cal
routine without saving any changes.
5. Once the known thickness value is being displayed, press the key to display
“1 of 2”, which sets the zero value and returns to the measurement screen.
NOTE: The internal zero of the TI-25MX is now set. The procedure above can be used
to set the internal zero of the TI-25MX to use any reference standard as the ‘probe zero’
standard if desired.
6. Repeat steps 2-4 on the second test point/location.
7. Press the key to display the calculated velocity edit screen.
NOTE: The calculated velocity can be edited, if needed, by pressing the keys to scroll
and edit the velocity value.
8. Press the key to set the calculated material velocity and return to the
measurement screen.
NOTE: CHECK YOUR CALIBRATION! Place the transducer back on the calibration
points. The thickness readings should now match the known thickness values with
minimal error. If the thicknesses are not correct, repeat the steps above.
Basic Material Type
If the material velocity is unknown, a sample thickness cannot be taken directly from
the material, but the general type of material is known, selecting a basic material type
from the common material (MATL) list in the TI-25MX would offer a reasonable
approximation of the thickness. There are 9 common materials and 2 user programmable
settings available. It’s important to note that these velocities will not always be an

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exact representation of the material being tested. Use these values only if a close
approximation is acceptable. Follow the steps below to select a basic material type:
Selecting a Basic Material Type
1. Press the key to access the material list. The edit icon will be illuminated
and ashing.
2. Use the and keys to scroll through the material options.
3. When the desired MATL setting is displayed, press the key to set the
material velocity and return to the measurement screen.
NOTE: Pressing the key prior to pressing the key will abort to the
measurement screen without saving any changes.
4. If USR1 or USR2 were selected, the velocity edit screen will be displayed and edit
icon illuminated and ashing.
5. Use the and keys to scroll to the desired material velocity.
NOTE: The longer these keys are held, the faster the velocity value is incremented.
6. When the desired velocity setting is displayed, press the key to set the material
velocity and return to the measurement screen.
NOTE: Pressing the key prior to pressing the key will abort to the
measurement screen without saving changes.