TESTING CRITICAL MEDICAL TUBING USING HIGH FREQUENCY EDDY CURRENT COILS.

Encircling coil eddy current testing of thin walled small diameter tube is inspected as it travels through a coil excited with one or more high frequency signals. The composition of the material under test influences the selection of the test frequency. Usually these materials have very low conductivity and small dimensions that require a high test frequency. In the past, these materials were tested at a maximum of 1 MHZ due to coil design and limitations to the input stages of electronics. With new electronics which are linear and coil designs which are low impedance, it is possible to test these materials with greater S/N (signal to noise) and use the phase response to reject mechanical, permeability and dielectric noise. This paper will discuss the advantages obtained by testing these types of materials at higher frequencies using new coils designs. Permeability is the ability of a material to concentrate magnetic flux. Soft iron is a material that is easily magnetized