Checkline MX-5 - Manual (Page 15)

MX-5 Ultrasonic Thickness Gauge
11
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 23 for information on transducer
selection.
While the transducer is in contact with the material that is being
measured, the MX-5 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 MX-5 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 thickness value is observed while the
transducer is in place, and another value is observed after the transducer is
removed.