DeFelsko PosiTector UTG v.3.1 Full Manual - Manual (Page 8)

5
The PosiTector UTG M 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
Coating
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 t
1
+t
2
+t
3
, 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).
Additionally, the PosiTector accepts a number of probe types
including magnetic and eddy current coating thickness, surface
profile, environmental and ultrasonic wall thickness probes.
Perform the latest software Updates (pg. 35) to ensure probe
compatibility with your Gage. For the latest information on probe
interchangeability see www.defelsko.com/probes