DeFelsko PosiTector UTG v.2.2 - Manual (Page 2)

Introduction Introduction
2
The PosiTector UTG ME is a hand-held Ultrasonic
Thickness Gage that uses the non-destructive ultra-
sonic pulse-echo principle to measure the wall thick-
ness of a wide variety of materials. The default and
most common setting for the PosiTector UTG is
multiple-echo (ME) mode. In ME mode the Gage
measures the metal thickness of a painted structure,
disregarding the paint thickness. The user can
switch the gage to single-echo mode by selecting SE
Mode from the Gage menu (see pg.15).
The probe (a single element contact transducer)
transmits an ultrasonic pulse into the material to be
measured. This pulse travels through the material
towards the other side. When it encounters an inter-
face such as air (back wall) or another material, the
pulse is echoed back to the probe. The time required
for the pulse to propogate through the material is
measured by the Gage, represented as t
1
and t
2
below.
In single-echo mode (see Figure 1) the Gage
determines thickness by measuring t
1
(uncoated) or
t
2
(coated), dividing it by two and then multiplying by
the velocity of sound for that material (steel).
steel
coating
steel
2
t >
1
t
For uncoated materials t
1
relates directly to material
thickness. When a material is coated the propaga-
tion time is increased and is shown above as t
2
.
Coatings such as paint have a slower velocity of
Figure 1
2
t
1
t
Probe
Probe