Checkline DFX-7 User Manual
Page 129
DFX-7
Ultrasonic Flaw Detector
125
10.11 Polarity
The DFX-7 is equipped with an option to select the polarity, or phase +/-, for the
purpose of detection. The phase can be a very valuable feature to have when the
signal returning from the test material is marginal, a low frequency transducer is
being used, and the user has a very weak positive or negative cycle, while trying to
measure very thick materials. There is a possibility that signal will become so weak
that it falls below the threshold, and peak jumps to the next cycle altogether. This
peak jump represents a shift of the detection further out in time, resulting incorrect
measurements. The material being measured will appear thicker than it actually is.
Refer to the diagram below: