Electromagnetic characterization of three RF leak detectors

Three electromagnetic leak detectors have been evaluated as quantitative hardness surveillance tools. The leak detectors included a low-frequency (150 kHz) twin-loop system that measured shielding effectiveness according to the MIL-STD-285 definition, a unit that used skin current injection and a ferrite coil sensor, and a transmitter/receiver that operated in the UHF range (462 MHz). First, the electromagnetic characteristics of the leak detectors were measured. Then the performance of the leak detectors was determined in the laboratory using a set of calibrated apertures whose shielding effectiveness had been predicted using polarizability theory. The leak detectors were used to measure the shielding effectiveness of hardened and unhardened apertures on a large commercial aircraft. It is noted that, with some modification to the operating procedures, each of the leak detectors could be used in a semiquantitative manner.<>