DeFelsko PosiTector 100 v.4.0 - Manual (Page 16)

Page 16 100 Series
A visual inspection, such as that obtained by microscopically viewing a cross-
sectional cut of the material, often reveals useful information about your
application. It may also explain why the Gage behaves the way it does when
measuring your part.
Finally, you are always welcome to contact us at [email protected] with
your inquiries. Be sure to include as much information about your application
and about the results obtained from known samples such as the plastic shims as
well as from the unknown material you are trying to measure. Provide us with
the Gage serial number and details about the material you are measuring and the
size and shape of the part. If all else fails you are welcome to send us a sample
of your application for measurement by our lab technicians.
Theory of Operation
The Model 100 uses an ultrasonic pulse echo principle. By transmitting an
ultrasonic pulse into the coating/substrate specimen and determining the time
taken for the pulse to travel to the coating/substrate interface and back to the
transducer, a coating thickness can be calculated.
The Gage transmits a high frequency, ultrasonic vibration into the coating using
a single element transducer. The vibration travels through the coating material
until a material with different mechanical properties is encountered, typically the
substrate. The vibration will be partially reflected and transmitted at the
interface between the dissimilar materials. The reflection will propagate back
through the coating and will be detected by the transducer. The transmitted
vibration will continue to travel into the substrate material and will also
experience reflections and transmissions at any material interfaces that are
encountered.
The transducer converts the reflections into an electrical signal which the Gage
digitizes. The digitized echo wave form is then analyzed to determine the exact
propagation time of the vibration.
Layer 1 is 2.5 mils thick. Layer 2 is 1.5 mils thick.
Layer 3 is 1.5 mils thick. Total thickness is 5.5 mils.
The most distinct interface is between layers 2 & 3.