Synthesis of inductive displacement-measuring system using computer-aided design

A rigorous method used to model linear variable differential transformers (l.v.d.t.s) is applied to a variable-inductance displacement transducer. This method known as `field modelling¿ uses a knowledge of the magnetic flux distribution within the transducer. This flux distribution is obtained from the solution of Maxwell´s equation, with boundary conditions deriving from the geometry and material properties of the transducer. The field equations are expressed in terms of the magnetic vector potential and, with the use of axial symmetry, reduced to an elliptic boundary value problem. This problem is approximated by finite-difference equations and solved, numerically, by the method of successive overrelaxation (s.o.r.). A transducer design is modelled, using this method, and the model is used in the synthesis of a displacement-measuring system. The sensitivity of the synthesised system is compared with experimental results obtained from a system with the same design specifications. The sensitivities of the two systems agree to within 2%. The design of the system is then altered, to improve sensitivity, and the sensitivities of the synthesised and experimental systems are again compared.