• Journal of Magnetics
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• v.17 no.3
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• pp.210-213
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• 2012

To detect the surface and the opposite side cracks on iron specimen under AC and DC magnetic fields, the planar inductive coil sensors were employed. When the induced signals were measured, the planar inductive coil sensor and the magnetic field source were lifted off about 2 mm from the top surface of the specimen. AC magnetic fields and DC magnetic fields were applied to the specimens by single straight Cu coil and NdFeB permanent magnet, respectively. The detected signals at crack positions were good coincidence with those of the simulation results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.868-874
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• 2011

In this paper, a new structure to improve the resolution of an inductive torque sensor is proposed. The new coupling structure and the change of number of turns for the receiving coil increase the resolution of the torque sensor. Because this torque sensor has non-contact points, it has no abrasion at the contact point, and is very durable. Also, the torque sensor has less variation due to vibration or strain, and it has a good EMC(Electromagnetic Compatibility) and thermal characteristics.

• Proceedings of the KWS Conference
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• 1994.05a
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• pp.171-174
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• 1994

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.5
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• pp.395-400
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• 2008

Alternating magnetic field was used for detection of surface flaws on nonmagnetic and magnetic metallic specimens. The nondestructive sensor probe was composed of the planar coil with inductive magnetic thin film yoke as a sensing component and a single straight typed exciting coil. The planar inductive coil sensor with magnetic yoke was fabricated by sputtering, electroplating, dry etching and photolithography process. The alternative currents with the range of 0.1A to 1.0A (0.7 MHz to 1.8 MHz) were applied to the exciting coil. The specimens were prepared with the slit shaped artificial surface flaws (minimum depth and width; 0.5 mm) on metallic plate (Al; nonmagnetic metal and FeC; magnetic metal). The detected signal for the positions and shapes of surface flaws on specimens were obtained with high sensitivity and high signal to ratio. The measured output signals by the non-contacted scanning on surface of FeC specimen with micron-sized crack were converted to the images of the flaws. And these results were compared with the optical images, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.232-239
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• 2008

The position sensors used in a magnetic bearing system are desirable to provide some degree of fault-tolerance as the rotor position is necessary for the feedback control to overcome the open-loop instability. In this paper, we propose an inductive position sensor that can cope with a partial fault in the sensor. The sensor has multiple poles which can be combined to sense the in-plane motion of the rotor. When a high-frequency voltage signal drives each pole of the sensor, the resulting current in the sensor coil contains information regarding the rotor position. The signal processing circuit of the sensor extracts this position information. In this paper, we used the magnetic circuit model of the sensor that shows the analytical relationship between the sensor output and the rotor motion. The multi-polar structure of the sensor makes it possible to introduce redundancy which can be exploited for fault-tolerant operation. The proposed sensor is applied to a magnetically levitated turbo-molecular vacuum pump. Experimental results validate the fault-tolerance algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.48-55
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• 2010

We have development the steering angle sensor using not only detecting parts but also integrating technique with semiconductors for automobile applications. The performance design and analysis of the steering angle sensor for intelligent vehicles is complicated due to variety of parameters. In this study, the performance characteristics of the angle sensor were analyzed using test rig. By means of magnetic induction technique, these new the steering angle sensors showed excellent magnetic characteristics. The detection range of steering angle sensor obtained was ${\pm}800^{\circ}$, the maximum non-linearity is 0.744% Full Span and the temperature range was $-40^{\circ}C{\sim}+125^{\circ}C$. With this conclusive, the inductive angle sensor was quite satisfactory for many applications in intelligent vehicles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.995-999
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• 2015

Inductive sensors are versatile and economical devices that are widely used to measure a wide variety of physical variables, such as displacement, force, and pressure. In this paper, we propose a simple inductive sensor consisting of a thin partial ring and a coil set. The self-inductance of the sensor was estimated using magnetic circuit analysis and validated through finite element analysis (FEA). The natural frequency of the ring was estimated using Castigliano's theorem and the method of equivalent mass. The estimation was validated through experiments and FEA. A prototype sensor with a signal processing circuit is built and applied to noninvasively sense the pressure inside a flexible tube. The obtained sensor outputs show quadratic behavior with respect to the pressure. When fitted to a quadratic equation, the least-square measurement error was less than 2%. The results confirm the feasibility of pressure sensing using the proposed inductive sensor.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.223-232
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• 2014

An inductive sensor system is proposed to detect the gear location and angular position of a geared shaft for automatic feeding of the shaft into the proper cutting position of the other end. The system consists of two set of coils, bridge circuit, signal condition circuit, and microprocessor. The coil sensors of the system measure changes of inductance along with the surface position of a geared shaft. The inductance changes are transformed to voltages by the bridge circuit, which are then conditioned and processed for the recognition of the gear. In order to incorporate with the experimental results with the sensor system, a finite element method (FEM) simulation for the magnetic field between the sensor and the shaft was carried out. The predicted results and the experiments revealed that the sensor system was appropriate for sensing the position of gear and the angular position of gear tooth of a geared shaft.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.524-530
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• 2008

The spin valve tunneling magnetoresistance (SV-TMR) sensor performance is analyzed using Stoner-Wohlfarth model for the detection of eddy current signals in nondestructive testing applications. The SV-TMR response in terms of the applied AC magnetic field dominantly generates the second harmonic amplitude in hard axis direction. The second harmonic eddy current signal detection using SV-TMR sensor shows higher performance than that of the coil sensor at lower frequencies. The SV-TMR sensor with high sensitivity gives a good solution to improve the low frequency performance in comparison with the inductive coil sensors. Therefore, the low frequency eddy current techniques based on SV-TMR sensors are specially useful in the detection of hidden defects, and it can be applied to detect the deeply embedded flaws or discontinuities in the conductive materials.

• Journal of Sensor Science and Technology
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• v.23 no.6
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• pp.409-415
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• 2014

We had presented an inductive type intraocular pressure sensor (L-sensor) in previous work. The distance between a micro coil and a ferrite on the membrane was modulated by pressure, and as a result the inductance and resonant frequency were changed. However, L-sensor has some problems to implant in eyes. First problem is low sensitivity. When L-sensor was implanted in rabbit's eyes, resonant frequency of L-sensor was very hard to detect. Second problem is biocompatibility. Size of L-sensor is $6{\times}7{\times}1.2mm$. When L-sensor was implanted in the eyes, it caused the inflammation. Therefore, this study suggests an inductive and capacitive type IOP sensor (LCsensor). The sensitivity of the LC-sensor 27.3 kHz/mmHg under 60mmHg. It is much larger than 14 kHz/mmHg of the L-sensor. And the size of LC-sensor is 47% smaller than L-sensor. After 2 weeks from the implantation of LC-sensor into rabbit eyes, we measured the changes of resonant frequency of LC-sensor according to increased IOP by Balanced Salt Solution (BSS) injection. As a result, the sensitivity of LC-sensor in in vivo test is 25 kHz/mmHg. That is similar to the sensitivity of in vitro test.