324 / | HD | ELECTRICITY: MEASURING AND TESTING |
200 | DF | MAGNETIC {24} |
228 | DF | .~ With means to create magnetic field to test material {5} |
239 | DF | .~.~ Induced voltage-type sensor {2} |
240 | DF | .~.~.~ Material flaw testing {2} |
241 | .~.~.~.~ Opposed induced voltage sensors |