An analytical model of the effect of external DC magnetic fields on the AC voltages of an LVDT

2010 IEEE Instrumentation &Amp; Measurement Technology Conference Proceedings

Martino

et al. 2010

Abstract-This paper proposes an automatic test bench, based on a rigorous and repeatable measurement procedure, for the analysis of a position sensor linear variable differential transformer (LVDT). The test bench allows complete characterization of an LVDT sensor working in an interfering magnetic field by evaluating the uncertainty and nonlinearity of the sensor. This issue is addressed in neither the sensor datasheet nor the scientific literature. The potential of the method and the performance of the automated test bench are proven by measuring the main sensor characteristics such as nonlinearity and uncertainty, and the error of a position reading due to external magnetic interference on two commercial LVDTs. The sensors are based on two different reading techniques, and both are analyzed using current and voltage excitations. In fact, the test bench permits to study the robustness of the sensor with respect to external magnetic fields by comparing position drifts due to interference at varying source excitations and reading techniques.Index Terms-Automatic testing, magnetic field effects, magnetic field measurements, magnetic variable measurements.

“…The variation of the primary voltage is less important in the case of a voltage excitation. Further details on the phenomenon model are given in [16]. …”

Section: Discussionmentioning

confidence: 99%

Automatic test bench for the measurement of the magnetic interference on LVDTs

Spiezia

2010 IEEE Instrumentation &Amp; Measurement Technology Conference Proceedings

Martino

et al. 2010

“…Anyway, an analytical model for the magnetic interference on LVDTs, when the supply is performed with a current signal, can be found in [15]. The study of an analytical model in voltage, together with further measurements with different materials and particular adjustments of simulation parameters are currently matter for future works.…”

Section: Discussionmentioning

confidence: 99%

Study of magnetic interference on a LVDT prototype

Masi

Danisi

2010 IEEE Instrumentation &Amp; Measurement Technology Conference Proceedings

et al. 2010

Self Cite

Abstract-This paper presents a prototype o Differential Transformer, which has been d and produced in order to observe, study an effects on its working of an external interfer The LVDT prototype has been first simulated conditions and in case of external interference, software FLUX. The design guidelines c simulations have been used to develop the complete set of measurements has been pe comparison between simulations and meas proposed.

“…Therefore, the low-frequency components will be filtered out, and no cross effect on the main harmonics will be present, with the whole system described in the model being linear. These performances have been experimentally observed in [12] and cannot be obtained with LVDTs due to the nonlinear ferromagnetic materials, whose permeability is modulated by the external field [7], [9], [10].…”

Section: B Derivation Of Electrical Magnitudesmentioning

confidence: 97%

“…whereas the sense voltages can be obtained, starting from (9) and considering I 2 = −I 1 = I, as follows:…”

Section: B Derivation Of Electrical Magnitudesmentioning

confidence: 99%

“…On the other hand, a transversal magnetic field has shown negligible influence on the LVDT position reading [6]. Analytical study of the phenomenon [9], characterizations through finite-element method (FEM) simulations [7], [10], and experimental measurement campaigns [7], [11] have demonstrated the unavoidability of this effect for typical LVDT structures due to the presence of ferromagnetic materials with a nonlinear B-H relation, which are part of the intrinsic design of an LVDT. Such nonlinearity between the field and flux densities makes even a dc or slowly varying magnetic field affect the harmonics of the sensor windings' voltages, therefore affecting the position reading.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Electromagnetic Analysis and Validation of an Ironless Inductive Position Sensor

Danisi

Masi

IEEE Trans. Instrum. Meas.

et al. 2013

Self Cite

Abstract-The ironless inductive position sensor is a linear position sensing structure, which exhibits intrinsic immunity to external magnetic fields since it is characterized by air-cored windings. This new solution may be of major interest for applications where external magnetic fields can be a source of interference. In this paper, an analytical model of the working principle of the sensor is proposed. The effect of the moving coil flux on the overall sensed magnetic flux is described. The model is preliminarily verified by simulations on a finite-element structure of the sensor, in order to assess its soundness. Finally, experimental measurements on a custom sensor's prototype give the definitive benchmarking of the model as a valid design tool, in the framework of the design and synthesis of the device.Index Terms-Air-cored coils, electromagnetic modeling, ironless position sensor, linear variable differential transformer (LVDT), mutual inductance.