Electromagnetic fields in relation to eddy current gauging
The work presented in this thesis describes some theoretical and experimental aspects of the relationships between electromagnetic fields and a non-contact type of eddy current gauge, which utilises a cylindrical solenoid and coaxially positioned metallic bar, either ferrous or non-ferrous. A rigorous mathematical analysis of the eddy current gauging system is presented, together with an evaluation of the solutions produced. This rigorous mathematical treatment is simplified, and the mathematical model thus produced is verified experimentally. The simplified mathematical model is used as a basis for a practical eddy current gauge operating at a frequency of 10 kHz, using ferrous or non-ferrous metal. A novel technique is then described in which the simplified mathematical model is used as part of a practical microprocessor-aided eddy current gauging system, which allows appropriate compensation to be introduced into the system for ferrous metallic conductors with magneticflaws present. This system uses a type of magnetic saturation technique.