Analysis of Sensor Effects for a Position Measurement System in Harsh Environments

Gruber, Günter; Neumayer, Markus; Schweighofer, Bernhard; Leitner, Thomas; Berger, Matthias; Klösch, Gerald; Wegleiter, Hannes

doi:10.1109/i2mtc48687.2022.9806484

Cited by 3 publications

(10 citation statements)

References 14 publications

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“…The impedance

is measured and depends on the displacement, the geometry of the sensing coil and the target, the temperature, the humidity, and the measurement frequency. Based on the ECM in Figure 2 , the impedance of the sensor,

, neglecting the capacitance

, can be derived as follows

and was previously determined in [ 9 , 22 ]. The first term in Equation ( 1 ) describes the influence of the sensing coil, and the second term in Equation ( 1 ) describes the joint influence of the target and the sensing coil on the impedance

.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…From the impedance

, we calculate the inductance

and substitute

with the time constant

[ 9 , 11 ]. The inductance of the sensor

can be described by the sensor model

where

describes the inductance of the air coil (in the absence of the target) that takes temperature drifts into account.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…The time constant

represents the electrical and magnetic properties of the target. This model description is found in [ 9 , 11 ].

can be seen as the coupling coefficient of an ideal ECDS, i.e., an ECDS that measures the distance to a target of infinite conductivity (

).…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…By choosing the product term

, as recommended in [ 8 , 9 ], the inductance

becomes more insensitive with respect to the properties of the target. For the resistance

, a dependence of the target and the sensing coil remains in the fraction term

in Equation ( 3 ).…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…Figure 1 depicts a typical ECDS, comprising a sensing coil and a target. The displacement x between the sensing coil and the target is determined from changes in the impedance

, particularly the change in inductance

[ 8 , 9 , 10 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

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Eddy Current Position Measurement in Harsh Environments: A Temperature Compensation and Calibration Approach

Gruber,

Schweighofer,

Berger

et al. 2024

Sensors

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Eddy current displacement sensors (ECDSs) are widely used for the noncontact position measurement of small displacements (lift-offs). Challenges arise with larger displacements as the sensitivity of the ECDSs decreases. This leads to a more pronounced impact of temperature variations on the inductance and, consequently, an increased position error. Design solutions often rely on multiple coils, suitable coil carrier materials, and compensation measures to address the challenges. This study presents a single-coil ECDS for large displacement ranges in environments with high temperatures and temperature variations. The analysis is based on a sensor model derived from an equivalent circuit model (ECM). We propose design measures for both the sensing coil and the target, focusing on material selection to handle the impact of temperature variations. A key part of improving performance under varying temperatures includes model-based temperature compensation for the inductance of the sensing coil. We introduce a method to calibrate the sensor for large displacements, using a modified coupling coefficient based on field simulation data. Our analysis shows that this single-coil ECDS design maintains a position error of less than 0.2% full-scale for a temperature variation of 100K for the sensing coil and 110K for the target.

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“…The impedance

, neglecting the capacitance

, can be derived as follows

.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…From the impedance

, we calculate the inductance

and substitute

with the time constant

[ 9 , 11 ]. The inductance of the sensor

can be described by the sensor model

where

describes the inductance of the air coil (in the absence of the target) that takes temperature drifts into account.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…The time constant

represents the electrical and magnetic properties of the target. This model description is found in [ 9 , 11 ].

can be seen as the coupling coefficient of an ideal ECDS, i.e., an ECDS that measures the distance to a target of infinite conductivity (

).…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…By choosing the product term

, as recommended in [ 8 , 9 ], the inductance

becomes more insensitive with respect to the properties of the target. For the resistance

, a dependence of the target and the sensing coil remains in the fraction term

in Equation ( 3 ).…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…Figure 1 depicts a typical ECDS, comprising a sensing coil and a target. The displacement x between the sensing coil and the target is determined from changes in the impedance

, particularly the change in inductance

[ 8 , 9 , 10 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

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