DeFelsko PosiTector UTG v.3.1 Full Manual - Manual (Page 10)

7
Surface Conditions Surface Conditions
Ultrasonic measurements are affected by the condition,
roughness and contour of the surface to be tested.
Measurement results may vary on coarse surfaces. Where
possible, it is recommended to seat the transducer on a smooth
flat surface that is parallel to the opposite side of the material.
On rough surfaces, the use of a generous amount of couplant
minimizes the surface effects and serves to protect the transducer
from wear, particularly when dragging the probe across a surface.
During scanning operations, the probe can be become physically
decoupled, that is physically separated, from the material, either
due to the rough and/or scaly surface of the material or due to
user operation. Avoid this by using the Smart Couple
TM feature
(pg. 17)
On smooth, uncoated metal surfaces the Gage
(in multiple-echo mode) may occasionally be unable to give a
measurement result even when the "coupled" symbol
appears. Use additional couplant and lighter pressure on the
probe when measuring. Alternatively, laying a plastic shim on the
surface with couplant applied to both sides to simulate a painted
surface will help produce a steel-only thickness measurement
(multiple-echo mode). Switching the Gage to single-echo SE
mode (pg. 16) will also help produce a steel-only thickness
measurement.
UTG M Probes: