A Linear Differential Inductive Displacement Sensor With Dual Planar Coils
TL;DR: In this paper, a non-contact displacement sensor employing a couple of planar coils etched on printed circuit boards (PCBs) and an E-type soft ferromagnetic core is proposed.
Abstract: A non-contact displacement sensor employing a couple of planar coils etched on printed circuit boards (PCBs) and an E-type soft ferromagnetic core is proposed here. The E-type soft ferromagnetic core moves over two triangular shaped spiral coils etched on a couple of PCBs. The variation in the inductances of the two coils has a cubic polynomial relationship with the displacement of the core. An appropriate signal conditioning technique operates on the inductances and provides an output that varies linearly with the displacement. The symmetrical structure of the sensor provides negligible cross axis sensitivity. Simulation studies and results obtained from a prototype sensor having a 70-mm range and a resolution of $2~\mu \text{m}$ , built and tested, establish the efficacy of the proposed technique. The worst-case nonlinearity observed from the prototype is 0.4%.
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TL;DR: In this paper, a distance sensor based on a spiral resonator (SR) label printed on a dielectric substrate and remotely interrogated through a small loop antenna acting as reader is presented.
Abstract: A distance sensor based on a spiral resonator (SR) label printed on a dielectric substrate and remotely interrogated through a small loop antenna acting as reader is presented. The proposed system is working at a single frequency (856.5 MHz) and could be compliant with conventional RFID readers. The measurement of distance is carried out by observing the magnitude variation of the response at resonance, namely the real part of the input impedance of the probing loop. Indeed, the latter response changes as a function of the distance between the tag and the loop due to the variation of mutual coupling between the pair. The proposed sensor is capable of providing estimates of the distance with high resolution within the specified range of operation. The results also show that the sensitivity of the sensor, which is quantified by the change of input impedance over distance, decreases at large displacements, eventually reaching a saturation point which defines the maximum detectable distance. The sensing principle is verified using simulations and measurements. It is also demonstrated that the maximum readable distance is comparable to the size of the SR. Finally, the effect of lateral displacement was investigated experimentally to demonstrate how the sensor performs in conditions where perfect axial alignment cannot be guaranteed. Thanks to its scalability potential, the proposed sensor is suitable for various practical scenarios.
21 citations
TL;DR: In this article , the authors investigated key factors of sensor structure and material, signal conditioning and interface, and fixtures for time drift to permanently installed applications, and compared two kinds of signal conditioning methods using resonance circuits and inductance-to-digital converter (LDC) chips.
Abstract: An edge displacement sensor is one of the key technologies for building large segmented mirror astronomical optical telescopes. A digital interface is one novel approach for sensor technologies, digital transformation and the Internet of Things (IoT) in particular. Frequency output sensors and inductance-to-digital converter (LDC) demonstrated significant advantages in comparison with conventional sensors with analog-to-digital converter (ADC) interfaces. In order for the differential inductive frequency output displacement (DIFOD) sensor to meet the high-stability requirements of segmented mirror astronomical telescopes, it is important to understand the factors for time drift of the sensor. This paper focuses on the investigation of key factors of sensor structure and material, signal conditioning and interface, and fixtures for time drift to permanently installed applications. First, the measurement principle and probe structural characteristics of the sensor are analyzed. Then, two kinds of signal conditioning and digitalization methods using resonance circuits and LDC chips are implemented and compared. Finally, the time drift stability experiments are performed on the sensors with different signal conditioning methods and fixtures under controlled temperature. Experimental results show that the magnetic shield ring effectively improves the sensitivity and quality factor of the sensors, the time drift stability of the sensor using the signal conditioning based on resonance circuits is better than that of the sensors using LDC chips, and the root mean square (RMS) of the sensor time drift meets the requirement of 0.01 μm/24 h. This study will help further development of high-stability of frequency output sensors and IoT-based systems for scaled-up applications in the future.
11 citations
TL;DR: In this paper, an improved driver circuit of eddy current sensor is proposed to generate a stable oscillating source with high stability and good precision of frequency, using a crystal oscillator circuit with power boost.
Abstract: Displacement sensor is the key component of the magnetic levitation system. Reducing complexity and improving reliability of the sensor circuits are very important to mass production of magnetic levitation devices. In this article, an improved driver circuit of eddy current sensor is proposed. In order to generate a stable oscillating source with high stability and good precision of frequency, a crystal oscillator circuit with power boost is used to replace the traditional Colpitts oscillator circuit. The improved modulation circuit is composed of passive components with a simple structure for improving reliability. The parameters design method of the modulation circuit is analyzed in detail, which greatly affects the sensitivity and linearity of the sensor. The experimental results show that the designed eddy current sensor has good linearity (1.12%) and sensitivity (2.14 V/mm), and it can ensure the stable operation of the magnetic levitated turbomolecular pump at the rated speed.
10 citations
TL;DR: In this paper , an absolute linear displacement sensor based on orthogonal dual traveling wave magnetic field is presented. But the measurement accuracy of the sensor is limited to ±15 ±15 µm within the measurement range of 0-80 mm.
Abstract: This paper presents an absolute linear displacement sensor, which is based on orthogonal dual traveling wave magnetic field. The sensor consists of two groups of field coils and inductive coils. Two groups of field coils with ‘ ${N}$ ’ and ‘ ${N}$ -1’ pitches generate two groups of traveling wave magnetic field which move in orthogonal directions. Then, the mixed magnetic field is picked up and induced by two groups of inductive coils. Two roads of electrical traveling wave signals are generated. Absolute position measurement is realized by comparing the phase differences of two groups of electrical signals. Compared with the traditional structure of the absolute sensor, the sensor combines dual tracks into a single track. Accordingly, the width of the sensor can be reduced. In order to be sensed effectively, dual traveling wave magnetic fields move orthogonally. The angular separations with the direction of measurement are 45° and −45°. The structure and measurement principle of the sensor are described in detail. A sensor prototype is fabricated by printed circuit board technology, and the experiment is brought out. The experimental results show that the sensor can achieve absolute displacement measurement, and the measurement accuracy is ± $15 ~\mu \text{m}$ within the measurement range of 0–80 mm.
8 citations
TL;DR: In this article, a novel displacement sensor with nanometric resolution based on magnetoelectric effect was developed, which combines equivalent magnetic circuit method and equivalent circuit method for magneto-lectric effects using the nonlinear constitutive parameters.
Abstract: Micro-displacement measurement is essential in precision fields, such as precision positioning, micro-vibration control and biological engineering. Conventional sensors have disadvantages of susceptibility to environmental, high cost and difficulty in integration. To address these deficiencies, this paper developed a novel displacement sensor with nanometric resolution based on magnetoelectric effect. Combining equivalent magnetic circuit method and equivalent circuit method for magnetoelectric effect using the nonlinear constitutive parameters, an equivalent circuit model of the proposed sensor is established to analyse and predict the performance of displacement sensor. Then a prototype of sensor based on Terfenol-D/PZT composites is fabricated, and the performance of prototype for dynamic displacement amplitude and static position measurement are tested. The results not only validate the developed equivalent circuit model, but also evidence the potential of magnetoelectric displacement sensor. Especially for dynamic displacement amplitude measurement, the resolution of it is better than 13.27 nm, which is close to or even beyond commercial laser displacement sensor.
8 citations
References
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TL;DR: In accordance with the sensor analysis presented in this paper, design strategies to compensate for important sensor imperfections are recommended and challenges that are associated with ECS interfaces are identified, with focus on advanced industrial applications.
Abstract: This paper presents a comprehensive study of the design aspects of eddy-current displacement sensor (ECS) systems. In accordance with the sensor analysis presented in this paper, design strategies to compensate for important sensor imperfections are recommended. To this end, the challenges that are associated with ECS interfaces are identified, with focus on advanced industrial applications. This paper also provides a technical overview of the design advances of ECS interfaces proposed in the last decade and evaluates their pros and cons. Recently reported interface solutions for demanding industrial applications with respect to high resolution, stability, bandwidth, and low power consumption, at a sufficiently high excitation frequency, are addressed in more detail.
120 citations
"A Linear Differential Inductive Dis..." refers background in this paper
...Design aspects for eddy current displacement sensors involving planar coils are discussed in [16]....
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TL;DR: In this paper, the authors present a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications.
Abstract: Noncontacting inductive sensors are applicable on a large scale for position detection or travel measurement in industrial applications. Reasons for such broad acceptance in many sectors of industry are noncontact and wear-free sensing of the target (any metal object), reliability and robustness, resistance to fouling, water tightness and compact size. The present work is intended to be a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications. It starts with the fundamentals of inductive sensing and presents the physical basics gained by modern analytic and simulation methods, as well as high-level integrated circuits for inductive sensors. The following sections deal with present-day inductive analog proximity sensors and with the distinctive technological innovation offered by the new inductive linear displacement sensors and with miniaturization results achieved through consistent integration.
112 citations
"A Linear Differential Inductive Dis..." refers background in this paper
...Most of the existing sensors employing a planar coil and a core to measure displacement are sensitive to vertical misalignments [13]–[17]....
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...Hence any misalignment in mounting of the sensors would lead to errors [13]–[17]....
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TL;DR: In this article, an absolute capacitive angular-position sensor with a contactless rotor is presented, which is mainly composed of three parts: the capacitive sensing element, a signal processor, and a microcontroller.
Abstract: This paper presents an absolute capacitive angular-position sensor with a contactless rotor. The sensor is mainly composed of three parts: the capacitive sensing element, a signal processor, and a microcontroller. The electrically floating rotor can be either conductive or dielectric. For the dielectric material, we chose plastic, and for the conductive rotor, we chose aluminum. The sensing element has a redundant structure, which reduces mechanical nonidealities. The signal processor has a multicapacitance input and a single output, which is a period-modulated square-wave voltage. The microcontroller acquires output data from the processor and sends them to a PC, which calculates the rotor position. Theoretical analysis, supported by experimental results, show that the sensitivity to mechanical nonidealities of the sensing element is higher in the case of a conductive rotor. The resolution of the capacitive angular-position sensor over the full range (360/spl deg/) was better than 1". The measured nonlinearity was /spl plusmn/ 100" and /spl plusmn/ 300" for the dielectric and the conductive rotor, respectively.
75 citations
"A Linear Differential Inductive Dis..." refers methods in this paper
...Different techniques of non-contact displacement sensing such as: resistive [1], capacitive [2], inductive [3]–[5] and optical [6] techniques are in vogue....
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TL;DR: In this paper, the authors proposed an error-compensation model that can effectively reduce the impact of the incident angle error of a laser displacement sensor (LDS) that measures accuracy.
Abstract: This paper proposes a novel error-compensation model that can effectively reduce the impact of the incident angle error of a laser displacement sensor (LDS) that measures accuracy. The laser triangulation method is an effective method of measurement. It is characterized by non-contact, large measuring range and high measuring efficiency. However, the measurement accuracy is affected by the incidence angle. To improve the measurement accuracy, a practical measurement strategy is presented. The experiment was carried out using a standard hard alloy ball calibration LDS. By introducing the error model, the experimental data were improved. Finally, in the application of an aero-engine blade measurement, the crossed curves method was used to calculate incidence angle of the measuring point. By comparing the LDS with a high-precision coordinate measuring machine (CMM) in experiments, the LDS accuracy is significantly improved; the results show that the laser measuring system has the thinner structure and higher efficiency than the CMM, so this paper is worth promoting.
61 citations
"A Linear Differential Inductive Dis..." refers methods in this paper
...Different techniques of non-contact displacement sensing such as: resistive [1], capacitive [2], inductive [3]–[5] and optical [6] techniques are in vogue....
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01 Jan 1995
TL;DR: In this paper, a very linear oscillator is used in the processing circuit to convert the position quantity to a period-modulated signal which can be read out directly by a microcontroller.
Abstract: A novel smart resistive-capacitive angular position sensor is presented. The main advantages of this low-cost system are its simplicity, high stability and high reliability. A very linear oscillator is used in the processing circuit to convert the position quantity to a period-modulated signal which can be read out directly by a microcontroller. The system does not need an A/D converter. The nonlinearity of the smart angular position sensor system is less than /spl plusmn/0.3% (/spl plusmn/0.9/spl deg/) over the range of 270. >
56 citations
"A Linear Differential Inductive Dis..." refers methods in this paper
...Different techniques of non-contact displacement sensing such as: resistive [1], capacitive [2], inductive [3]–[5] and optical [6] techniques are in vogue....
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