DeFelsko PosiTector 100 v.4.0 - Manual (Page 36)

Page 36 100 Series
Measuring Notes
Rough Substrates
In smooth coating/substrate conditions where there is a distinct interface, the
echo is clear and sharp. This results in a repeatable measurement with a sharp,
narrow peak on the graphical display. When the substrate has a surface
consisting of many peaks and valleys, numerous and varied echoes are received
from the interface.
The Model 100 tends to average these reflections and presents them graphically
as a wide peak. Although successive measurements are not repeatable, they
should be close, depending upon the amount of roughness. It is a good idea to
use a statistical average (
Modes
q q
Statistics ON - pg.12) to determine
thickness. When peak and valley depths are consistent, sometimes a “shoulder”,
or attached peak, is visible. This secondary peak can be measured by positioning
the cursor (
Setup q
q Gate/Zoom Control - pg.32) over it.
Transition Layers
Some coatings “blend” into previous coats or into the substrate. This indistinct
interface produces an echo that is neither clear nor sharp. In these situations it is
difficult to obtain a repeatable measurement. The graphical display shows a
wide peak with a rounded top.
In this occurrence, the Gage received the strongest echo from the
peaks and measured the coating thickness as 25.7 mils. The cursor
has been turned on and located over the 2
nd
attached peak to
estimate the coating thickness over the valleys as 28.4 mils.