KERN & SOHN TN 60-0.01EE - Manual (Page 7)

TN_EE-BA-e-1410 7
The transducer is the “business end” of the instrument. It transmits and receives ul-
trasonic sound waves that the instrument uses to calculate the thickness of the mate-
rial being measured. The transducer connects to the instrument via the attached ca-
ble, and two coaxial connectors. When using transducers, the orientation of the dual
coaxial connectors is not critical: either plug may be fitted to either socket in the in-
strument.
The transducer must be used correctly in order for the instrument to produce accu-
rate, reliable measurements. Below is a short description of the transducer, followed
by instructions for its use.
Left figure is a bottom view of a typical transducer. The two semicircles of the bearing
face are visible, as is the barrier separating them. One of the semicircles is responsi-
ble for conducting ultrasonic sound into the material being measured, and the other
semicircle is responsible for conducting the echoed sound back into the transducer.
When the transducer is placed against the material being measured, it is the area
directly beneath the center of the bearing face that is being measured.
Right figure is a top view of a typical transducer. Press against the top with the thumb
or index finger to hold the transducer in place. Moderate pressure is sufficient, as it is
only necessary to keep the transducer stationary, and the bearing face seated flat
against the surface of the material being measured.
Tabelle Nr. 3-1 Suitable Measurement head
Model
Frequence
MHz
Φmm
Measurement
range Lower limit Annotation
P5EE
5 10 P-E: 2~600 mm
E-E:3~30/60 mm
Φ20 mm×3,0 mm Standard
measurement
3.2 Condition and Preparation of Surfaces
In any ultrasonic measurement scenario, the shape and roughness of the test sur-
face are of paramount importance. Rough, uneven surfaces may limit the penetration
of ultrasound through the material, and result in unstable, and therefore unreliable,
measurements. The surface being measured should be clean, and free of any small
particulate matter, rust, or scale. The presence of such obstructions will prevent the
transducer from seating properly against the surface. Often, a wire brush or scraper
will be helpful in cleaning surfaces. In more extreme cases, rotary sanders or grind-
ing wheels may be used, though care must be taken to prevent surface gouging,
which will inhibit proper transducer coupling.
Extremely rough surfaces, such as the pebble-like finish of some cast iron, will prove
most difficult to measure. These kinds of surfaces act on the sound beam like frosted
glass on light, the beam becomes diffused and scattered in all directions.
In addition to posing obstacles to measurement, rough surfaces contribute to exces-
sive wear of the transducer, particularly in situations where the transducer is
“scrubbed” along the surface. Transducers should be inspected on a regular basis,
for signs of uneven wear of the bearing face. If the bearing face is worn on one side
more than another, the sound beam penetrating the test material may no longer be