Checkline TI-MINIMAX - Manual (Page 42)

Dakota Ultrasonics
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Bolt ends with recessed grademarks, as shown at left of Figure 3. Couplant
can be used to fill recessed grademarks. Small indentations cause some loss
of signal strength, but normal measurement is still possible. Large or
numerous indentations cause the signal to be too weak for a reliable
measurement.
•
Bolt ends with raised grade marks, or indentations with a raised edge, which
cause the transducer to be seated at an angle to the axis of the bolt, thus
preventing adequate contact, as shown at right of Figure 3.
Figure 3 Effect of lowered and raised grade marks
6.3 Bolt end reflectors
Smooth, flat reflecting bolt ends that are perpendicular to the axis of the bolt are
required for accurate echo reception. Bolt ends may need to be cleaned, ground,
etc. to achieve the required surface.
Note: Misalignment exceeding 2 degrees can cause significant errors.
Avoid:
•
Rough reflecting bolt ends. As shown in Figure 4, if the reflecting end of the
bolt is rough or curved, most of the reflected energy will be dispersed and a
weak or distorted echo will be received.
•
Reflecting bolt ends not perpendicular to the axis of the bolt. Sonic energy will
be reflected toward the sidewall of the bolt, as shown in Figure 5.
•
Nonperpendicular reflecting bolt ends due to bending of the bolt as shown in
Figure 6.