Dakota Ultrasonics VX - Manual (Page 14)

Dakota Ultrasonics
10
If the Stability Indicator has fewer than five bars darkened, or the
numbers on the display seem erratic, first check to make sure that there is
an adequate film of couplant beneath the transducer, and that the
transducer is seated flat against the material. If the condition persists, it
may be necessary to select a different transducer (size or frequency) for
the material being measured. See page 17 for information on transducer
selection.
While the transducer is in contact with the material being measured, the
VX will perform four measurements every second, updating its display as it
does so. When the transducer is removed from the surface, the display will
hold the last measurement made.
IMPORTANT
Occasionally, a small film of couplant will be drawn out between the
transducer and the surface as the transducer is removed. When this
happens, the VX may perform a measurement through this couplant film,
resulting in a measurement that is larger or smaller than it should be. This
phenomenon is obvious when one value is observed while the transducer
is in contact with the material, and another value is observed after the
transducer is removed.