constant voltage transformers, and if electrical interference on the a/c. circuit is suspected, special transformers are
available to block such interference.
Figure 5-65. Double Shield for Reducing External Noise Signals.
For most applications ultrasonic techniques used in the field are established at the depot or ALC. In certain situations
it may be necessary to develop a technique in the field. If such a need arises, the following information will aid in
developing the required techniques. The information may also lead to a better understanding of established techniques.
When establishing an ultrasonic inspection technique, it is first necessary to obtain as much information as possible
about the test part. Information required is as follows:
a. Type of material to be inspected, and heat treatment.
b. Surface condition.
d. Shape/geometry of test part.
e. Type of discontinuity to look for.
f. Expected location of discontinuity.
g. Expected orientation of discontinuity with respect to sound path.
h. Acceptance/rejection criteria.
i. Inspection method required.
j. Inspection zones, if applicable.