DeFelsko PosiTector UTG Full Manual page 8

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t
Probe
1
Figure 1
t
For uncoated materials relates directly to material thickness.
1
When a material is coated the propagation time is increased and
t
is shown above as .
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
The PosiTector UTG M and UTG P in multiple-echo mode
determine thickness by measuring the time between at least three
consecutive back wall echoes.
Probe
t t
1 2 3
Figure 2
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
six and then multiplying by the velocity of sound for that material.
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t
Probe
2
t t
>
2 1
+
metal thickness.
t t
1
2 3
t t t
+ + , dividing it by
1 2 3
5
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