Study of Magnetic Interference on an LVDT: FEM Modeling and Experimental Measurements

Static or slowly varying magnetic fields can affect the performances of linear variable differential transformer by inducing a position reading drift. The problem is barely addressed in LVDTs' datasheets, and no quantitative information on the induced error is given. An LVDT finite element model is here presented together with its experimental validation in order to propose a tool for the study of the effects of external magnetic fields on LVDTs and for the design of less sensitive devices. The LVDT model has been validated in standard working conditions and in presence of an external magnetic field by means of a complete set of experimental measurements performed on a custom prototype, manufactured following the FEM guidelines.

[1]  Daniele Marioli,et al.  Application of an FFT-based algorithm to signal processing of LVDT position sensors , 1998, IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222).

[2]  Gary R. Consolazio,et al.  Finite Elements , 2007, Handbook of Dynamic System Modeling.

[3]  S. C. Saxena,et al.  A self-compensated smart LVDT transducer , 1989 .

[4]  G. Spiezia,et al.  Design of a Linear Variable Differential Transformer With High Rejection to External Interfering Magnetic Field , 2010, IEEE Transactions on Magnetics.

[5]  J. Simkin,et al.  Engineering analysis for design optimisation of differential transformers , 1988 .

[6]  Alessandro Masi,et al.  Automatic Test Bench for Measurement of Magnetic Interference on LVDTs , 2011, IEEE Transactions on Instrumentation and Measurement.

[7]  I. K. Kang,et al.  Some Concepts Concerning the New High‐Permeability 50–50 Nickel—Iron Alloys , 1967 .

[8]  K. Ara.  A Differential TransformerWith Temperature- and Excitation-Indep endent Output , 1972 .

[9]  A. Masi,et al.  LHC Collimators Low Level Control System , 2007, IEEE Transactions on Nuclear Science.

[10]  Y. Kano,et al.  New linear variable differential transformer with square coils , 1990, International Conference on Magnetics.

[11]  Alessandro Masi,et al.  An analytical model of the effect of external DC magnetic fields on the AC voltages of an LVDT , 2010, 2010 IEEE Instrumentation & Measurement Technology Conference Proceedings.

[12]  E. Sykulska,et al.  Application of finite element modelling in LVDT design , 1992 .

[13]  R. M. Ford,et al.  Test and comparison of LVDT signal conditioner performance , 2000, Proceedings of the 17th IEEE Instrumentation and Measurement Technology Conference [Cat. No. 00CH37066].

[14]  A. Masi,et al.  LVDT Conditioning on the LHC Collimators , 2008, IEEE Transactions on Nuclear Science.