8
mvip@mitech-ndt.com
counts while it is not highlighted.
Transducer Model:
Current transducer model setting in the instrument
Sound Velocity:
Current sound velocity setting
Thickness Reading
：
Display present single time measured value.
means exceeding upper
measuring limit.
means lower than bottom measuring limit.
Units Label
：
When the
mm
symbol is on, the instrument is displaying the thickness value in
millimeters and the sound velocity value in
m/s
. When the
in
symbol is on, the instrument is
displaying the thickness value in inches and the sound velocity value in
inch/us
.
2.4 Keypad Definitions
Turn the instrument
on and off
Exit from current
selection
Turn on/off the EL
backlight
Enter
Probe
Zero
operation
Plus or scroll up
Switch
selection
among items
Minus or scroll
down
Data Save or Data
Delete
3 Preparation
3.1 Transducer Selection
The gauge is inherently capable of performing measurements on a wide range of materials,
from various metals to glass and plastics. Different types of material, however, will require the use
of different transducers. Choosing the correct transducer for a job is critical to being able to easily
perform accurate and reliable measurement. The following paragraphs highlight the important
properties of transducers, which should be considered when selecting a transducer for a specific
job.
Generally speaking, the best transducer for a job is one that sends sufficient ultrasonic energy
into the material being measured such that a strong, stable echo is received by the gauge. Several
factors affect the strength of ultrasound as it travels. These are outlined below:
Initial Signal Strength. The stronger a signal is to begin with, the stronger its return echo will
be. Initial signal strength is largely a factor of the size of the ultrasound emitter in the transducer. A
large emitting area will send more energy into the material being measured than a small emitting
area. Thus, a so-called “1/2 inch” transducer will emit a stronger signal than a “1/4 inch”
transducer.
Absorption and Scattering. As ultrasound travels through any material, it is partly absorbed. If
the material through which the sound travels has any grain structure, the sound waves will
experience scattering. Both of these effects reduce the strength of the waves, and thus, the
gauge’s ability to detect the returning echo. Higher frequency ultrasound is absorbed and
scattered more than ultrasound of a lower frequency. While it may seem that using a lower
frequency transducer might be better in every instance, low frequencies are less directional than
high frequencies. Thus, a higher frequency transducer would be a better choice for detecting the
