DAKOTA ULTRASONICS PZX-7 User manual

OPERATION MANUAL
DAKOTA ULTRASONICS
P
PZ ZX X- -7 7
Precision Ultrasonic
Thickness Gauge
P/N P-307-0002 Rev 1.00, January 2019

CONTENTS
CHAPTER ONE INTRODUCTION ...................................................................... 1
1.1 DISCLAIMER ......................................................................................................................... 1
CHAPTER TWO KEYPAD, MENU, DISPLAY & CONNECTORS ..................... 2
2.1 ON/OFF/ENTER KEY… ..................................................................................................... 2
2.2 PRB 0 KEY… ....................................................................................................................... 2
2.3 CAL KEY…. ......................................................................................................................... 3
2.4 GAIN KEY…. ....................................................................................................................... 3
2.5 SCAN KEY…. ...................................................................................................................... 3
2.6 +/- INCREMENT/DECREMENT KEY’S…. .................................................................................. 3
2.7 MODE KEY…. ..................................................................................................................... 3
2.8 MENU KEY… ...................................................................................................................... 4
2.9 THE DISPLAY ....................................................................................................................... 5
2.10 TOP & BOTTOM END CAPS ................................................................................................. 8
CHAPTER THREE PRINCIPALS OF ULTRASONIC MEASUREMENT ......... 10
3.1 TIME VERSUS THICKNESS RELATIONSHIP ............................................................................. 10
3.2 SUITABILITY OF MATERIALS ................................................................................................. 10
3.3 RANGE OF MEASUREMENT AND ACCURACY .......................................................................... 10
3.4 COUPLANT ......................................................................................................................... 10
3.5 TEMPERATURE ................................................................................................................... 11
3.6 MEASUREMENT MODES ...................................................................................................... 11
CHAPTER FOUR SELECTING THE MEASUREMENT MODE ....................... 13
4.1 WHICH MODE & TRANSDUCER DO I USE FOR MY APPLICATION? ............................................ 13
CHAPTER FIVE MAKING MEASUREMENTS ................................................. 15
5.1 PROBE ZERO ...................................................................................................................... 15
5.2 MATERIAL CALIBRATION ..................................................................................................... 16
CHAPTER SIX THROUGH PAINT MEASUREMENT - MULTIMODE ............. 2 3 
6.1 INTRODUCTION ................................................................................................................... 23
6.2 MULTI MODE TRANSDUCERS .............................................................................................. 23
CHAPTER SEVEN VELOCITY GAUGE ........................................................... 25
7.1 VELOCITY GAUGE (VX) ....................................................................................................... 25
7.2 CALIBRATION TO A KNOWN THICKNESS ................................................................................ 26

7.3 CALIBRATION TO A KNOWN VELOCITY .................................................................................. 27
CHAPTER EIGHT ADDITIONAL FEATURES ................................................. 29
8.1 GAIN ................................................................................................................................. 29
8.2 HIGH SPEED SCAN ............................................................................................................. 30
8.3 ALARM ............................................................................................................................... 31
8.4 DIFFERENTIAL .................................................................................................................... 32
8.5 UNITS ................................................................................................................................ 33
8.6 LITE ................................................................................................................................... 34
8.7 BEEP ................................................................................................................................. 35
8.8 PROBE TYPE ...................................................................................................................... 36
8.9 VELOCITY (VX) .................................................................................................................. 37
8.10 LOCK ............................................................................................................................... 38
8.11 FACTORY DEFAULTS ........................................................................................................ 39
CHAPTER NINE CONNECTIVITY & POWER ................................................. 40
9.1 CONNECTIVITY ................................................................................................................... 40
9.2 INSTALLING SERIAL DRIVER (CDC) ..................................................................................... 40
9.3 LINE POWER ...................................................................................................................... 42
APPENDIX A - VELOCITY TABLE .................................................................. 43
APPENDIX B- APPLICATION NOTES ........................................................... 45

1
CHAPTER ONE
INTRODUCTION
The Dakota Ultrasonics model PZX-7 is a precision ultrasonic micrometer. Based on
the same operating principles as SONAR, the PZX-7 is capable of measuring the
thickness of various materials with accuracy as high as  0.0001 inches, or  0.001
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.
Dakota Ultrasonics maintains a customer support resource in order to assist users
with questions or difficulties not covered in this manual. Customer support may be
reached at any of the following:
Dakota Ultrasonics Corporation
1500 Green Hills Road, #107
Scotts Valley, CA 95066
Tel: [phone]
Fax: [phone]
www.dakotaultrasonics.com
1.1 Disclaimer
While the PZX-7 is a basic digital instrument, it is equipped with a number of
measurement modes and transducer options for additional versatility. It is strongly
recommended that the contents of this manual be read in its entirety to avoid
erroneous measurements based on operator error. The user is solely responsible for
proper use, setup and interpretation of the measurements acquired.

2
CHAPTER TWO
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 PZX-7 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 fixed value. Refer to page 15 for
further explanation of this important feature.

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2.3 CAL Key
The CAL key is used to enter and exit the PZX-7's calibration mode. This mode is
used to adjust the sound velocity value that the PZX-7 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 page 16 for an
explanation on the various calibration options.
2.4 GAIN Key
The PZX-7 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 five gain settings (VLOW, LOW, MED, HIGH, VHI) when pulse-echo or
thin PLAS mode is selected, and three gain settings (LOW, MED, HIGH) for all other
modes where automatic gain control is used. Refer to page 29 for details regarding
the gain feature.
2.5 SCAN Key
The PZX-7 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 to page 30 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 MODE Key
The MODE key toggles the measurement modes. If a delay line transducer (dLY) is
selected from the PROB menu option, echo-echo (E-E) and interface-echo (I-E)
modes will be toggled. If a contact transducer (Con) is selected, pulse-echo (P-E)
and echo-echo (E-E) modes will be toggled. Finally, if the plastic transducer (PLAS)
option is selected, the thickness options thin (thin) and thick (thK) will be toggled. The
measurement modes and transducer styles offer the flexibility to address specific

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application scenarios. Refer to page 11 for an explanation on the various calibration
options.
2.8 MENU Key
The MENU key is used to access and set all of the additional features of the PZX-7
that are not at the top level of the keypad with a dedicated key. The features and
setting are outlined in the table below:
Menu Feature Items:
Matl Scan Alarm Diff Unit Lite Beep Probe VX
Aluminum On On On English On On Delay On
Steel Off Off Off Metric Off Off Plastic Off
Stainless Options Options Options Options Contact
Iron Set Lo Set
Nominal
Low Lo Options
*
Plexiglass Set Hi High Med .125
PVC High .250
Plastic .375
Poly Urea .500
User 1
User 2
* Diameter options are only available for contact transducers.
Here’s a quick overview of navigating through the various features in MENU:
Navigating the Features in Menu
1) Press the key once to enter the sub menu items.
2) Press the keys to toggle through the features.
3) To enable or edit the status of any feature, press the key.
4) The edit icon will start blinking to indicate that the PZX-7 is currently in EDIT
mode.
5) Press the keys to toggle through the setting options.

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6) Press the key to accept changes and return to the top level of
features, or the key at any time to abort changes and return the
measurement screen.
2.9 The Display
The PZX-7 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:
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 group of icons indicates which measurement
mode the PZX-7 is currently using. The modes are pulse-echo, echo-echo,
interface-echo, and plastics (PLAS).
D. Stability/Repeatability Indicator: This is used in conjunction with the
thickness measurement as a reference for the validity of the measurement.
The PZX-7 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 PZX-7 has remaining.

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F. Backlight : When this icon is illuminated, it indicates the backlight is on.
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 PZX-7 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 PZX-7 DL. In P-E
mode the options are VLOW, LOW, MED, HIGH, VHI, and LOW, MED, HIGH
with modes E-E, I-E, and PLAS. MED is the default setting.
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. The plus/minus icon is illuminated when the DIFF
(differential) feature is activated.
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 PZX-7, Refer to page 4 for a list. The PZX-7 can be locked
once calibrated, to avoid accidently changing the calibration. When this icon is
illuminated, the PZX-7 is in lock mode. Refer to page 38 for an explanation on
locking the PZX-7.

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Delay Line Contact
The Transducer is the “business end” of the PZX-7. It transmits and receives
ultrasonic sound waves that the PZX-7 uses to calculate the thickness of the material
being measured. The transducer connects to the PZX-7 using a single shielded
coaxial cable with microdot connectors.
Delay Line Transducer
The single element delay line transducer is commonly used with the PZX-7 for
materials with an approximate range of 0.006” to 1.00” in steel. The measurement
modes used with this style of transducer are echo-echo (E-E) and interface-echo (I-
E). Echo-echo mode will be used for the lower end of the measurement range, while
interface-echo for the upper end of the measurement range. Interface-echo mode
measures from the end of the delay line to the first return echo from the back wall of
the material, while echo-echo measurements are made between the first and second
return echoes from the back wall of the material. The frequency range for the
versions Dakota commonly supply are from 10MHz to 20MHz.
The Delay line is fastened to the transducer with a retaining ring. A drop of couplant
is applied between the delay line and transducer body. Refer to the diagram above.
The couplant should be checked on a regular basis to keep it from drying out. To
replenish, unscrew the retaining ring counterclockwise, separate the delay line from
the body, ‘clean both surfaces’, apply a drop of couplant, and reassemble.
Delay Line Graphite Tip (For use with Plastics Mode)
The PZX-7 has a special “PLAS” mode that uses the standard delay line transducer,
as described above, but with a replaceable graphite delay tip. This mode and tip
should be used when the velocity of the plastic material measured is similar to the
velocity of the standard acrylic delay tip, and not achieving any signal/measurement.
The graphite tip creates a ‘mismatch’ between the tip material and the plastic material
measured.
The Delay line is fastened to the transducer with a retaining ring. A drop of couplant
is applied between the delay line and transducer body. Refer to the diagram above.
The couplant should be checked on a regular basis to keep it from drying out. To

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replenish, unscrew the retaining ring counterclockwise, separate the delay line from
the body, ‘clean both surfaces’, apply a drop of couplant, and reassemble.
Contact Transducer
The single element contact style transducers are commonly used for materials with
an approximate range of 0.040” to the maximum range of the PZX-7 rated in steel
and depending on the transducers diameter and frequency. The frequency range is
5.0 to 10 MHz, with diameters available at 0.125, 0.250, 0.375 and 0.500 inches.
The measurement modes used with this style of transducer are pulse-echo (P-E) and
echo-echo (E-E).
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" fluid, commonly called "couplant". This fluid serves to "couple", or
transfer, the ultrasonic sound waves from the transducer, into the material, and back
again. Before attempting to make a measurement, a small amount of couplant
should be applied to the surface of the material being measured. Typically, a single
droplet of couplant is sufficient.
After applying couplant, press the transducer (wear face down) firmly 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 PZX-7 has been
properly "zeroed" (see page 15), only if P-E mode is currently selected, 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 five bars darkened, or the numbers on the
display seem erratic, first check to make sure that there is an adequate film of
couplant beneath the transducer, and that the transducer is seated flat against the
material. If the condition persists, it may be necessary to select a different transducer
(size or frequency) for the material being measured. See page 13 for information on
transducer selection.
While the transducer is in contact with the material that is being measured, the PZX-7
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.
2.10 Top & Bottom End Caps

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The top end cap is where all connections are made to the PZX-7. 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 PZX-7’s top end cap. The transducer connector is a Lemo “00”.
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 firm contact.
Important: Be sure the battery polarity is correct, which can be found on the back
label of the PZX-7.
Note: Rechargeable batteries can be used, however they must be recharged outside
of the unit in a standalone battery charger.
USB-C Connector
Refer to Diagram: The USB-C connector, located on the bottom end cap, is a mini
type C female connector. It is designed to connect directly from the PZX-7 to a
standard USB type A port on a PC. The cable supplied with the PZX-7 is a USB type
C to a USB type A (pt# N-003-0330). See page 40 for information on connectivity.
Note: This connector is also used to upgrade the PZX-7 with the latest version of
firmware.

10
CHAPTER THREE
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 difficult include some cast materials,
concrete, wood, fiberglass, and some rubber.
3.3 Range of measurement and accuracy
The overall measurement capabilities, based on the wide variety of materials, are
determined by the consistency of the material being measured (homogeneity). 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 and
frequency. 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 efficiently. 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. Multi-echo techniques
offer temperature compensation to help minimize these errors.
3.6 Measurement Modes
This section will cover the different measurements modes of the PZX-7, the
transducers required, and the reasons for using specific modes:
Pulse-Echo (P-E) Mode:
Pulse-echo mode measures from the initial pulse (sometimes referred to as an
artificial zero) to the first echo (reflection). In this mode, a manual zero using the disk
(battery cover) will need to be performed prior to calibrating the PZX-7. The
transducer is placed on the reference disk located on top of the PZX-7, and the PRB
0 key pressed to establish a zero point for the transducer connected.
Errors from surface coatings and temperature variations can occur in pulse-echo
mode. Therefore, coatings should be removed, and frequent probe zero’s should be
performed if experiencing temperature gradients.
Echo-Echo (E-E) Mode – Through paint
The echo-echo mode measures between the first and second return
echoes/reflections. This mode is most commonly used with the high frequency delay
line style transducers for thin materials, and will also eliminate compensate for
temperature. This technique will also eliminate error due to epoxy based coated
surfaces by eliminating the error from the coating and measuring only the second
layer or base material without having to remove the coating. The disadvantage is

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that two return echoes are required to effectively measure the test material. As a
result, the type and thickness of the coating will affect the ability to achieve a
successful measurement. Both delay line and contact style transducers can be used
for through paint/coating measurements.
Interface-Echo (I-E) Mode
The interface-echo mode measures from the end of the “‘interface/delay line” to the
first return echo/reflection. This mode can be used for thicker materials up to 1”, and
for attenuative materials that don’t produce a sufficient second echo. The standard
measuring range is approximately 0.060” up to 1.00” rated in steel, and offers
temperature compensation for the heating and cooling of the transducer itself.
Plastics (PLAS) Mode
The plastics mode is a special setup for measuring thin plastics using a modified
interface-echo mode. When the standard acrylic delay tip is similar in velocity to the
plastic material measured, a return echo is not possible. Simply replacing the acrylic
tip with our graphite tip and using the ‘plastics’ mode will provide the necessary
mismatch necessary to measure the plastic successfully. The approximate range is
0.005” up to 0.300” depending on the type of plastic measured. This mode
additionally offers temperature compensation for the heating and cooling of the
transducer.

13
CHAPTER FOUR
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. Thicker cast
iron and plastics applications will generally require lower frequencies depending on
the material type and thickness. Frequencies from 2.25MHz to 10MHz are common.
Larger diameters offer greater penetration power based on the size of the crystal.
Thin Materials & Tough Access Areas
The high frequency delay line transducers are suitable when measuring thinner
consistent materials that pass sound easily, such as steel, aluminum, titanium, etc.
They offer temperature compensation with a suitable range up to 1” depending on
the delay line used. Replaceable cone tip options are also useful for difficult access
areas and diameters.
Thru Paint & Coatings
It’s common that users will be faced with applications where the material will be
coated with some type of protective paint or other epoxy based material. Since the
velocity of the coating is approximately 3 times slower than that of steel, pulse-echo
mode will produce an error if not removed. However, echo-echo mode can be used
with either delay line or contact style transducers to eliminate the error from the
coating, and measure only the base material. High damped or high frequency
transducers are most suitable for echo-echo measurement mode.
Plastics
Thin plastics are best suited using the delay line transducer with either the acrylic
delay tip in echo-echo or interface-echo modes. If the plastic measured is similar in
velocity to the acrylic tip and not measuring adequately, the replaceable graphite tip
and plastics mode will serve as the best option. Thicker plastics will generally require
a lower frequency contact style transducer for additional penetration. Increasing the
diameter of the transducer will also offer greater output.
High temperature
High temperature applications will require a special delay line material that isn’t as
absorptive of temperature.
Noisy Material
Materials such as titanium, stainless steel, and aluminum may have inherent surface
noise issues (mirroring effect). This can be avoided using a high frequency delay line

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transducer in either echo-echo or interface-echo modes. If using a contact style
transducer, a high frequency option should be considered.
Restricted access
Measuring materials with extreme curvatures or restricted access are best suited for
higher frequencies and smaller diameter transducers or tip options.

15
CHAPTER FIVE
MAKING MEASUREMENTS
The steps involved in making measurements are detailed in this section. The
following sections outline how to setup and prepare your PZX-7 for field use.
In pulse-echo mode the probe zero must be performed on the reference disk (battery
disk) attached to the top of the instrument. This compensates for variation in the
transducer. In all modes the sound velocity must be determined. The sound velocity
is used to convert the transit time to a physical length. The sound velocity can be
selected from the material chart at the end of this manual, or for greater precision
determined by measuring and calibrating from a known thickness of the actual
material. 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 on page 16.
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 is not used, and considered a ‘two-point’ calibration
described on page 19.
5.1 Probe zero
A probe zero is only necessary if a contact style transducer is used in pulse-echo
mode, and the contact option is enabled in the menu. A probe zero should be done
prior to calibrating the instrument, and done on a periodic basis when a temperature
gradient is an issue. If the PZX-7 is not zeroed correctly, all measurements will be in
error by some fixed value. In order to perform a probe zero, you must be in pulse-
echo mode.
Setting the zero point of the PZX-7 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 PZX-7 is not zeroed correctly, all the measurements taken may be
in error by some fixed value. The zero can only be performed with the measurement
mode set to pulse-echo (P-E). Therefore, if the PZX-7 is to use the echo-echo (E-E)
measurement mode and a manual zero is being performed, the PZX-7 will argue by
briefly displaying the message “ERR”.
The procedure to zero the transducer is outlined as below:
Performing a Manual Probe Zero (On Block)

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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 briefly be
displayed on the screen, indicating the zero calculation is being performed.
5.2 Material Calibration
In order for the PZX-7 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 PZX-7 provides three simple methods for setting the sound-
velocity outlined below:
Known Velocity
If the material velocity is known, it can be manually entered into the PZX-7, rather
than have the PZX-7 calculate the velocity value using a known thickness of the
same material type. The steps for entering the velocity are outlined below:
Using a Known Material Velocity