mvip@mitech-ndt.com
The transducer is the “business end” of the instrument. It transmits and receives ultrasonic
sound waves that the instrument uses to calculate the thickness of the material being measured.
The transducer connects to the instrument via the attached cable, 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 instrument.
The transducer must be used correctly in order for the instrument to produce accurate,
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 wearface are
visible, as is the barrier separating them. One of the semicircles is responsible 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 wearface 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 wearface seated flat against the surface of the material
being measured.
3.2 Condition and Preparation of Surfaces
In any ultrasonic measurement scenario, the shape and roughness of the test surface 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
grinding 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 excessive 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 wearface. If
the wearface is worn on one side more than another, the sound beam penetrating the test material
may no longer be perpendicular to the material surface. In this case, it will be difficult to exactly
locate tiny irregularities in the material being measured, as the focus of the sound beam no longer
lies directly beneath the transducer.
4 Startup
4.1 Power Supply
Two AA size alkaline batteries are needed as the power supply.
The battery compartment is situated at the instrument back. The cover is fastened with two