DeFelsko PosiTector 100 v.4.0 - Manual (Page 17)

100 Series Page 17
Since a potentially large number of echoes could occur, the Gage will choose the
strongest echo for use in coating thickness measurements. The assumption is
that the coating/substrate interface will provide the largest distance corrected
echo within the bracketed echo window (as defined by Gates A and B). The
coating thickness is calculated from the measured propagation time and the
velocity of propagation (sound velocity constant, v
s
) of the coating material. The
velocity of propagation is determined during optimization of the Gage against a
known coating thickness standard (pg.26).
The Model 100 uses deconvolution techniques to filter and enhance closely
spaced digitized echoes. These techniques make it possible to measure thin
coatings and coatings on acoustically similar substrates.
A menu is provided that allows an operator to select from a number of pre-
configured coating and substrate classes. Using these class selections, the Model
100 can quickly be optimized to different coating/substrate combinations.
Couplant
Unless the coating is soft, couplant is required by the probe to transmit the
ultrasonic pulse into the coating. Water is an ideal couplant for smooth coatings.
Use the supplied glycol gel for rougher coatings. While it is unlikely that the
couplant will damage the finish or leave a stain on the surface, we suggest
testing the surface by using the couplant on a sample. If testing indicates that
staining has occurred, a small amount of water can be used instead of the
couplant. Consult the enclosed Material Safety Data Sheet and your coating
supplier if you suspect the couplant may damage the coating. Other liquids such
as liquid soap may also be used.
Power-up / Power-down
When any of the LCD buttons is depressed the Model 100 powers-up, performs
a self test and displays the last measurement(s). It then waits for the probe
switch to indicate the beginning of a measurement cycle. To preserve battery life
the Gage automatically powers-down after 2 minutes of inactivity when
operating on battery power or 8 minutes when operating off the optional AC
adapter (pg.35). There is no OFF button. All settings and readings are
maintained during power-down including the last measurement.