Eddy Current Probe Performance Requirements

Abstract : This study resulted in the development of a procurement specification for single-coil, absolute eddy current probes (shielded and nonshielded) which are used by the USAF with the Hocking UH-B (or equivalent) instruments for inspection of aluminum airframe structures. The specification was necessary because the USAF currently has no adequate means of assuring the quality of eddy current probe performance. The specification establishes minimum performance requirements and associated test methods for determining performance. It also establishes a standard nomenclature for the salient features of probes and a standard probe numbering system that allows the basic characteristics of the probes to be identified on the probe in a uniform manner. A simplified field test procedure for these probes which incorporates a subset of the tests in the specification was also developed. To establish performance requirements for the specification, the major parameters determining probe performance were defined. Acceptance limits for these parameters were guided by measurements from 30 shielded and 30 nonshielded probes. The probes were obtained from USAF inventory at numerous Air Force bases and were representative of proves in current use. The acceptance limits were set to reject probes with poor performance and not reject a high percentage of probes with typical performance. Keywords: Flaw detection probe standards; Electrical measurement test methods.