POSITECTOR UTG Quick Manual
Quick Guide v. 3.0
Ultrasonic Thickness Gage
Advanced model
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Introduction
Introduction
The PosiTector UTG is a hand-held Ultrasonic Thickness Gage
that uses the non-destructive ultrasonic pulse-echo principle to
measure the wall thickness of a wide variety of materials. It
consists of a body (Standard or Advanced) and probe (UTGC or
UTGM, see pg. 2).
The PosiTector UTG powers-up when the center navigation
button is pressed. To preserve battery life, the instrument
powers down after approximately 5 minutes of no activity. All
settings are retained.
1. Remove the protective rubber cap from the probe.
2. Power-up Gage by pressing the center navigation button.
3. Zero the probe (see pg. 6)
4. Select the correct velocity of sound (see pg. 7)
5. Measure the part (see pg. 3)
Quick Start
Quick Start
Typical Display
Current
Measurement
Currently
selected
material
Unit of
Measurement
The Coupled Symbol appears when the
probe is ultrasonically connected with a
surface.
inch
Steel
Battery
Icon
Measurement
Mode currently set
to multiple-echo
(UTGM probe only)
1
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2
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Probes
Probes
PosiTector UTG probes transmit an ultrasonic pulse into the
material to be measured. This pulse travels through the material
towards the other side. When it encounters an interface such as air
(back wall) or another material, the pulse is reflected back to the
probe. The time required for the pulse to propogate through the
material is measured by the Gage, represented as t1and t2 below.
PosiTector UTGC and UTGM (in single-echo mode) probes
determine thickness by measuring t1(uncoated) or t2 (coated),
dividing it by two and then multiplying by the velocity of sound for
that material (steel). See Figure 1.
For uncoated materials t1relates directly to material thickness.
When a material is coated the propagation time is increased and
is shown above as t
2
.
Coatings such as paint have a slower velocity of sound than that
of metal. Thus the single-echo technique will produce a thickness
result greater than the actual combined coating+metal thickness.
steel
coating
steel
2
t
>
1
t
Figure 1
2
t
1
t
Probe
Probe
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How to Measure
How to Measure
The PosiTector UTGM in multiple-echo mode determines
thickness by measuring the time between at least three consecutive back wall echoes.
steel
Probe
1
t
2
t
3
t
1
t
2
t
3
t
Co
a
ting
Figure 2
Probe
In the figure above, multiple-echo mode measures only the time
between echoes. Regardless of whether the steel is coated or not,
all times between echoes are the same. In multiple-echo mode
the Gage determines thickness by measuring t1+t2+t3, dividing it
by six and then multiplying by the velocity of sound for that material. The resultant thickness calculation made by the instrument is
therefore an accurate measurement of the steel thickness only,
disregarding the coating thickness.
The velocity of sound is expressed in inches per microsecond or
meters per second. It is different for all materials. For example,
sound travels through steel faster (~0.233 in/µs) than it travels
through plastic (~0.086 in/µs).
1. Remove rubber cap from probe. Couplant (glycol
gel - included) must be applied to the surface to be
tested to eliminate air gaps between the wear face
and the surface. A single drop of couplant is sufficient
when taking a spot measurement.
2. Place the probe flat on the surface. Use moderate pressure to
press against the top of the probe with the thumb or index finger.
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