16
#2
#1
Coating
Substrate
Probe
Couplant
Measurement of dense (hard) coatings.
A significant echo occurs at the probe/coating
interface. The relative strength of this echo
compared to the coating/substrate echo requires that
Gate
A
be increased.
Measurement of total thickness in multi-layer
coating applications.
Multiple coating/coating/substrate interfaces may
generate several echoes. The user may need to
adjust Gates to ignore echoes from coating/coating
interfaces.
limits of the gage and assumes the largest “echo” is
the coating/substrate echo (single coating
applications only). Adjustable measurement Gates
have been provided for the user to force the
instrument to ignore echoes from unwanted
boundaries within the sample. Several examples
below help to illustrate the use of Gates for specific
applications.
Measurement of coatings with rough surfaces.
When rough coatings are measured, the gage
typically identifies the thickness from the top of the
coating peaks down to the substrate (#1). Couplant
fills the voids between the probe and the coating (#2)
creating an additional interface. If echoes from the
couplant/coating interface (#2) are stronger than the
coating/substrate interface (#1), an adjustment
(increase) of Gate
A
may be required for the gage to
display the weaker (#1) echo.
