Design of a Linear Variable Differential Transformer With High Rejection to External Interfering Magnetic Field

The sensitivity of linear variable differential transformer (LVDT) position sensors to external slowly varying magnetic fields represents a critical issue when these sensors are installed close to high-current cables or electrical motors with significant fringe fields. The resulting position error can reach several hundreds of micrometers against a specified uncertainty normally below a few micrometers. In this paper, the design of a LVDT position sensor with high rejection to external constant or slowly varying magnetic fields is addressed by exploiting the finite element method (FEM) simulator FLUX. A shield, isolated from the sensor's magnetic circuit, has been considered to reduce the effect of magnetic fields on the secondary voltages of the LVDT. In addition, a dc current is used in order to polarize the magnetic circuit to reduce the sensitivity of the sensor to external interferences.

[1]  Jan K. Sykulski,et al.  FINITE ELEMENT MODELLING OF INDUCTIVE SENSORS , 1992 .

[2]  S. Marshall,et al.  An analytic model for the fluxgate magnetometer , 1967 .

[3]  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].

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

[5]  I. Sasada,et al.  Orthogonal fluxgate mechanism operated with dc biased excitation , 2002 .

[6]  Shang-Teh Wu,et al.  An LVDT-based self-actuating displacement transducer , 2008 .

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

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

[9]  G. Panda,et al.  A novel method for designing LVDT and its comparison with conventional design , 2006, Proceedings of the 2006 IEEE Sensors Applications Symposium, 2006..

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

[11]  P. Odier.  DCCT technology review , 2004 .

[12]  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).

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