The Eddyliner™ P, Eddynomic™ and Eddysort™ Eddy current instruments operate on differential coils. Two separate coils are required for testing. One (the measuring coil) reads the characteristics of the part being tested. The other (the compensation coil) provides a compensating electrical vector. The instrument measures the differential voltage between the two at several selected frequencies. Resultant voltages of the complex impedance planes are displayed on either a CRT or LCD display and are stored in computer memory. Locus curves develop for the spread of frequencies, creating specific patterns for the materials characteristics under review.

There are important advantages of this method compared to the single coil (absolute) approach. Changes of differential vector are more pronounced, resulting in better resolution and greater precision. Drift is virtually eliminated. Temperature stability is enhanced.

Introducing new technologies, ibg has succeeded in compensating temperature fluctuations between measuring and compensation coils tenfold over previous practice.

For more information see ibg’s website at